Introduction to Anthropology Textbook Chapter 4 Biological Evolution and Early Human Evidence

Biological Evolution and Early Human Evidence . Figure The Grand Gallery of Evolution in the National Museum of Natural History in Paris , France displays specimens of the estimated millions of species that currently live or once lived on the Earth in its collections . In addition to educating the public about the mechanisms of evolution , the exhibitions in the museum honor the scientists who helped contribute to our current understanding of the history of life on Earth . credit Great Gallery of Evolution by Mustang , Public Domain ) CHAPTER OUTLINE What Is Biological Anthropology ?

What in a Name ?

The Science of Taxonomy It All in the Genes ! The Foundation of Evolution Evolution in Action Past and Present What Is a Primate ?

Origin of and of Primates Our Ancient Past The Earliest INTRODUCTION This chapter applies evolutionary concepts to the understanding of human origins and explains the biological variation seen in our ancestors across time . Chapters , Biological Evolution and Early Human Evidence and Chapter , The Genus Homo and the Emergence of Us , represent a of study that is probably the most dynamic , controversial and highly debated of anthropology . Perspectives and opinions vary not only within the mindset of the general public but also amongst scientists and

98 Biological Evolution and Early Human Evidence anthropologists alike . As the human fossil puzzle begins to in with new discoveries , we ourselves gaining valuable insights into what makes us human and the ways in which we are a part of , not separate from , the natural world . Despite our advances in the , we also have to be prepared for the possibility we may end up with more questions than answers ! It is these very reasons that explain why so many of us this such a fascinating and why so many of us take it so personally . It is after all a journey into the discovery of who we are and where we came from and that should be of interest to all of us as members of the Home genus . What Is Biological Anthropology ?

LEARNING By the end of this section , you will be able to Identify the of biological anthropology . Explain how each of the contributes to our understanding of human origins and evolution . Understand the historical context of the of biological anthropology . Looking to the Deep Past Biological anthropology , also referred to as physical anthropology or evolutionary anthropology , is one of the four major of anthropology . While the other focus on current and relatively recent human cultures , biological anthropology looks to the deeper past , asking questions about what it means to be human by exploring where humans came from as a species . Biological anthropology comprises numerous areas of study human biological variation , paleoanthropology ( human and primate evolution ) the study of nonhuman primates ) the study of bones found at archaeological sites ) and genetic anthropology ( the application of molecular science to archaeological , historical , and linguistic evidence to reveal the history of ancient human origins and migration ) Each of these areas of study contributes something to anthropologists understanding of current human physical characteristics and behaviors . Exploring What It Means to Be Human Studies of human biological variation evaluate the physical similarities and differences between human populations across both time and space . Differences in morphology include features such as height , jawline , eye sockets , and ear and nose shape and size . Biochemical differences account for variations in the sense of smell , mutations in the gene that offer resistance to HIV , and variations in skin pigmentation in response to levels of exposure to ultraviolet rays from the sun . FIGURE These variations in modern human skin pigmentation are the result of evolutionary adaptations to different levels of exposure to ultraviolet rays from the sun . credit School Diversity Many Hands Held Together by Wonder , BY ) The study of human biological variation is closely linked to the original conception of biological anthropology , Access for free at

which was formalized in 1930 with the establishment of the American Association of Physical Anthropologists , recently renamed the American Association of Biological Anthropologists . The change in name is an effort to move away from the term physical anthropology , which has come to be associated with views promoting racism that no longer represent or align with views held by anthropologists today . In 1951 , American anthropologist Sherwood introduced a new physical anthropology , changing the focus from racial typology and to the study of human evolution and the evolutionary process . This new focus expanded anthropology as a to include paleoanthropology and Paleoanthropology looks at the fossil evidence of humanity ancestors along with ancient material culture such as tools and other human artifacts . The physical morphology ( shape and size ) of skulls and other material ( skeletal remains other than the skull ) allow to form hypotheses about important milestones in human evolution over time . examines the behavioral and physical attributes living and fossil primates as well as their relationships with their environments . Humans are primates who share a common ancestry with nonhuman primates . By studying nonhuman primates , anthropologists can gain a better understanding ofwhat it means to be a primate and what it means to be human . Genetic anthropology is used within several areas anthropology . In this specialized area , DNA testing is combined with archaeological , historical , and linguistic evidence to reveal the history of ancient human migration or to track human disease . Forensic anthropology is a of biological anthropology that applies methods to the analysis of human remains for the purposes of identifying a victim and determining the possible cause of death . A major difference between forensic anthropology and other types of biological anthropology is that forensic anthropology is usually focused on crime scenes involving the death of an individual , whereas other types primarily focus on understanding patterns and features that may appear in a group or an entire population . Beginning in World War II , forensic anthropologists have been instrumental in helping identify victims ofwar and disasters . They have played critical roles in identifying victims of the Thailand tsunami in 2004 and the destruction of the World Trade Center on September 11 , 2001 . Today , most forensic anthropologists work in a medical examiner , assisting with autopsies and examinations of skeletal remains . studies human remains in archaeological settings with a focus on what skeletal material can reveal about the culture , diet , and presence in a population . are also interested in the system of a population , which helps anthropologists better understand the roles of environmental and ecological pressures and in shaping cultural identity , social inequity , sustainability , and access to and use of resources . Based on the biological remains found at archaeological sites , explore questions pertaining to social and funerary behavior , diet and nutrition , health , and disease . offers a window into the connections among biology , society , and culture . An example of what a might study is skeletal evidence of infant cranial boarding , which was practiced by many cultures , including the ancient Maya , the Inca , and some Native North American groups . The process involved binding a child head to a board in order to deform the skull , possibly to meet an aesthetic ideal or to signify social status . have found that variations in how the board was attached to the skull provide important information about an individual social identity .

FIGURE This elongated skull is from a member of the culture , which flourished in what is now Peru in the years 100 to 800 CE . It long , oval shape is the result of infant cranial bonding , the practice of deliberately shaping the development of an infant skull by bonding it to stiff boards . credit Peru Deformed Skull by , BY ) SE PROFILES IN ANTHROPOLOGY Ann Rosalie David FIGURE Professor Ann Rosalie David , and forensic and biological anthropologist at the University of Manchester , UK . credit Professor David , Public Domain ) Personal History Professor Ann Rosalie David was born in Cardiff , UK and earned a bachelor of arts degree in ancient history from University College London in 1967 and a doctorate from the University of Liverpool in 1971 . Her thesis was on ancient Egyptian temple rituals .

Area The focus of Professor David work has been biological anthropology and . Accomplishments In the Field Professor David is a Director of the Centre for Biological and Forensic Studies in at the University of Manchester . In this role , she established the Ancient Egyptian Mummy Tissue Bank , one of the only such tissue banks in the world . She served as the keeper of at the Manchester Museum and has often worked in collaboration with Egypt Ministry of Health and Population on public health projects . One such project involved the of antibodies against schistosomiasis , a parasite spread by freshwater snails , in Egyptian mummies . David was made an of the Order of the British Empire ( OBE ) in 2003 for her work in . David has appeared in or consulted on several documentaries , including the television miniseries Private Lives ofthe Pharaohs ( 2000 ) and Secrets ofthe Pharaohs ( 2001 ) and the documentary short Mummies Secrets ofthe Pharaohs ( 2007 ) Importance of Her Work Ann Rosalie David was the woman in Britain to hold a professorship in . She was a pioneer in biomedical research , conducting research on disease , diet , and lifestyles in ancient Egypt . In 2010 , her work on ancient Egyptian mummies found evidence to suggest that cancer may be a disease , attributable in part to modern pollution and changes in lifestyle and diet ( David and 2010 ) PODCAST In this ( Professor Rosalie discusses her work with ancient Egyptian mummies . What in Name ?

The Science of Taxonomy LEARNING OUTCOMES By the end of this section , you will be able to Describe the historical context of binomial nomenclature and . Distinguish between the different categories of groups found in . Explain the different of species and how they are applied to different populations . the Science of Taxonomy Taxonomy is as the and naming of things . Taxonomy organizes things into groups based on criteria . The criteria can be as simple as color or height or as complex as the presence or absence of a trait , gene , or behavior . Taxonomy is a critical component of biological anthropology because it helps anthropologists organize humans and their evolutionary ancestors both spatially ( by location ) and temporally ( through time ) Taxon refers to a subgroup , such as the genus . is the plural form of taxon , used to refer to all groups . The system used for organizing living organisms was originally developed in the century by Swedish botanist Carolus . His system , which he called the , uses a structure known as binomial nomenclature . Binomial nomenclature assigns two Latin names to each organism . The is termed the genus name . The second is the or the trivial name , commonly called the species name . In print , genus and species names are . The letter of the genus is capitalized , while the species or trivial name is lowercase . For example , the name for the house cat is Felis cams , and the name for modern human beings is Homo . binomial nomenclature established a shared language that would become universal across countries and cultures , avoiding the confusion caused by regional and colloquial names . In addition to establishing a shared language , naming system groups organisms that share common traits . For example , he grouped together animals with mammary glands into the category mammals . Mammals were further broken down according to other traits . For example , mammals that have opposable

thumbs were grouped together as primates , and those without opposable thumbs were grouped as non primates . This is a hierarchical scheme , meaning that organisms are grouped into successive levels from the broadest category to the more level of species . When created his , he built hierarchical levels into his taxonomy kingdom , class , order , genus , and species . Humans are in the kingdom , the class , the order Primates , the genus Homo , and the species sapiens . Over time , many levels have been added to the system of , including domain , phylum , subclass , superorder , family , and tribe . The addition of these taxon groups has enabled biological anthropologists to better understand the variations present in various groups of organisms . However , biological anthropologists spend the majority of their time trying to understand the species level . Kingdom Phylum Class Lepidoptera Family FIGURE This chart details the hierarchical for the monarch butterfly . The broadest category , Life , appears at the top of the chart , with of increasing at each level that follows . Species is the most granular level . attribution Copyright Rice , under By license ) Species While species is a word that most people are familiar with and comfortable using , just what determines a species is incredibly to . At the most basic level , a species comprises a group of organisms with shared characteristics that distinguish them from other groups . Most scientists distinguish a species based on behavior , genetics , morphology . Species are the basis for names . The common name of a species , on the other hand , is usually based on general physical characteristics noted by a culture or local population . Common names are also referred to as folk taxonomy or ( by culture , There is a growing interest among anthropologists and the community in preserving Indigenous of the natural world and connecting them with . Decisions related to often involve tremendous taxonomical controversy , especially within the of biological anthropology . There are more than 20 distinct species , or ways of categorizing or distinguishing one type of organism from another . Below are the four most common of a species . Biological Species The biological species states that a species is a group of interbreeding organisms that are

reproductively isolated from other groups of organisms . Reproductive isolation means that members of a species are not able to mate successfully with members outside their species . Gorillas , for example , can not successfully breed with Pan paniscus , the bonobo . The biological species uses the ability to interbreed as its foundation because successful mating leads to gene , or the movement of genetic material from one population to another . Ecological Species The ecological species emphasizes the role of natural selection in maintaining species boundaries . This concept is based on the idea that gene is neither necessary nor to maintain species boundaries . Instead , natural selection plays an important role in maintaining the boundaries between species . In nature , species boundaries are often maintained even though there is a substantial amount of gene between species . Gene between species generally occurs at places called hybrid zones , areas of overlap where two species are known to successfully breed . A classic example of a hybrid zone occurs on the island of in Southeast Asia , where maura ( the moor macaque ) and ( the macaque ) are known to have successfully for more than 150 years . Despite this , the integrity of the two distinct species has been maintained . Phylogenetic Species The biological species is based on breeding behavior , whether species are capable of mating with one another . This foundation is problematic when trying to identify species over time . It is hard to know whether two fossil specimens were capable of interbreeding . It is also in the fossil record to distinguish between variation ( differences between members of two different species ) and variation ( variation within a species ) Imagine the bones of two individuals , one feet tall and the other six feet four inches . Identifying whether these individuals were members of two different species ( variation ) or representative of the normal variation within a given species would be extremely challenging . These problems are addressed by the phylogenetic species . The phylogenetic species states that a species can be determined by shared possession ofone unique characteristic . For example , imagine you found a group of fossil leg bones . In order to decide if they were from the same species , you would need to determine if they had a trait in common that only these fossil leg bones possessed . If the bones all possessed trait A and this trait was not found in any other species already , then you would have a new species , and all of the fossil leg bones could be placed in that species . Mote Recognition Species The mate recognition species states that a species is a set of organisms that recognize one another as potential mates . A classic example of a group of species that can be distinguished using this is American crickets . Within a single habitat in the United States , there might be over 30 different species of crickets . Each species of cricket is known to produce a distinct song . Despite all these different species living side by side , the female cricket of each species will only mate with a male after hearing the male sing her song . The song , and the female recognition of it , constitutes a mate recognition system . This is analogous to the biological species in that the song acts as a reproductive isolating mechanism . All in the Genes ! The Foundation of Evolution LEARNING OUTCOMES By the end of this section , you will be able to alleles , genes , and . Distinguish the process of mitosis from the process of meiosis . Explain how laws of heredity affect human variation . Explain how the multitude of evolutionary forces contribute to variation in the human condition . The Units of Life Cells are the basic units of life in all organisms . They are the smallest entities that are capable of reproduction . There are two main types of cells and cells , named for the types of

organisms in which they occur . are organisms , such as bacteria and . are more complex , multicellular organisms , such as plants and animals ( including humans ) One of the most important components of cells is the enclosed nucleus at the center of the cell cells do not have this nucleus . The nucleus of a cell houses all of the genetic material , or DNA ( deoxyribonucleic acid ) that controls cellular function . Normally , the DNA forms a long string within the nucleus . There are two main types of cells somatic cells and sex cells ( also known as ) The somatic cells make up the structural components of a body , such as the tissues , muscles , and organs . The sex cells are involved in reproduction . The function of the sex cells is to unite with a sex cell from another individual to form a fertilized egg , also known as a zygote . In animals , there are two types of sex cells ova , or eggs , and sperm . Cell division is the process that results in the production of new cells . However , sex and somatic cells divide differently . The cellular division of somatic cells is known as mitosis , while the cellular division of sex cells is known as meiosis . Mitosis of somatic cells is sometimes referred to as simple cell division because the parent cell divides once to produce two daughter cells that are genetically identical to each other and identical to the original parent cell . During mitosis , the DNA genetic material forms structures known as chromosomes . Each daughter cell inherits an exact copy of all 46 chromosomes found within the parent cell . Two diploid DNA cells replication , mi Mitosis FIGURE In somatic cell division , also known as mitosis , the parent cell divides to produce two daughter cells that are genetically identical to each other and to the parent cell . credit Major events in mitosis by Commons , Public Domain ) Meiosis , or sex cell division , is more complicated . This type of cellular division only occurs in the testes of males and the ovaries of females . Instead ofjust one division , meiosis results from two cellular divisions that produce four daughter cells . In meiosis , the four daughter cells each receive half of the original genetic material from the parental cell . Thus , each daughter cell only has 23 chromosomes . It is on the chromosomes that genes are housed . Genes are the fundamental unit of heredity . They are best understood as the sequence or ordering of the DNA material that is housed in the nucleus . The genotype is the genetic material found within an organism cells and it is the expression of these genes that will produce the phenotype or observable trait . Sometimes , the sequencing of the DNA material produces a variation of a gene , known as an allele . An allele is defined as a similar but slightly different form of the same gene that can activate the expression of a trait . Gregor and the Laws of Heredity The true nature of inheritance was not really understood until the beginning of the century , when the work of Gregor , a Catholic priest from , was rediscovered . While in college , Gregor was introduced to cell theory , which states that all organisms are composed of cells and that cells are the fundamental unit of all living things . Cell theory raised many questions in mind , including whether both parents contribute equally to the cells in their offspring . In 1854 , began a series of experiments with pea plants to help resolve this question and better understand how traits are inherited from generation to generation .

It All in the Genes ! The Foundation of Evolution FIGURE Gregor was a Catholic priest whose experiments with selective breeding of pea plants established many of the rules of heredity . credit Gregor Monk by William , Principles of A Commons , Public Domain ) The stage of experiments was identifying plants that breed true , meaning that each parent only produces one kind of offspring when . A is essentially a some plants , such as peas , have both male and female parts and can . Not all are the same as the parent plant , however . For example , pea plants that have yellow pods sometimes produce offspring with yellow pods and sometimes produce offspring with green pods . continued to selectively breed only those pea plants that produced offspring that were the same as the parents . He called them and referred to them as the generation . It took him more than two years to establish plants that always bred true . Then selected seven traits of his pea plants that each had two distinct , or observable expressions of the trait . For example , seed shape can be either round or wrinkled , while pod color can be either yellow or green . Over the next eight years , studied the mating and resulting traits of more than plants . round of experiments used his purebred pea plants to create what is known as a monohybrid cross . A monohybrid cross is a mating between two purebred individuals who differ in a single characteristic . In monohybrid crosses , the parent pea plants differed from one another in terms of whether the pods of the parental pea plants were yellow or green or whether the seeds of the parental pea plant were wrinkled or round . 105

Characteristics of pea plants Gregor used in his inheritance experiments Seeds , Stem position form of size yellow ' roundish axial long wrinkled green green terminal short the seeds FIGURE a number of distinct characteristics observable in the seeds , flowers , pods , and stems of pea plants . He used these observable traits as the basis for his breeding experiments , taking note of which traits were dominant and which unexpressed ( or recessive ) in offspring . credit Genetics by Commons , Public Domain ) In his first monohybrid crosses , mated a purebred yellow pea plant with a purebred green pea plant . He found that all the offspring resulting from this monohybrid cross were yellow , even though when the green peas , all their offspring were green . In other words , all the hybrid offspring were yellow in color . A hybrid plant is one in whose parents differ in a term of a characteristic , such as pod color or seed shape . The trait that was expressed ( yellow ) referred to as dominant , and the trait that disappeared ( green ) he referred to as recessive . next set of experiments involved mating two hybrid other words , those that resulted from the monohybrid cross . In these experiments , he found that the recessive traits reappeared in a ratio of three dominant to one recessive . Kev Purebred Yellow Hybrid Yellow Purebred Green FIGURE These diagrams are examples of squares , a simple method for predicting the observable results of breeding experiments . In the top square , a purebred green plant ( is crossed with a hybrid yellow plant ( The four possibilities for offspring appear in the four interior squares of the diagram . In this case , half of the offspring will be hybrid yellow and half will purebred green . The bottom diagram shows the results of a cross between a purebred green and a purebred yellow plant in this case , all offspring are hybrid yellow . credit Copyright Rice , under BY license ) experiments suggested two very important facts . First , noted that various expressions ofa trait ( such as pea color ) were controlled by discrete units that occur in pairs and that offspring inherited one

unit of each pair from each parent . This observation became law of inheritance , the law of segregation , which states that the two alleles for each trait segregate , or separate , during the formation of ( eggs and sperm ) and that during the reproductive process , the alleles combine at random with other alleles . Today , we know that the process of of sex law of segregation . Each of the seven traits by is controlled by a pair of genes in the plant , one on each chromosome . During the reproductive cycle , the chromosomes separate from one another so that each gamete has only one allele for each trait . During fertilization , the alleles combine , and the state is restored . After established his first law of inheritance , he extended his studies to more complex situations . He began performing experiments with two set of traits , using dihybrid crosses . A dihybrid cross is a cross between individuals who differ with respect to two gene example , a cross between a plant with a round yellow pea and a plant with a wrinkled green pea . Because yellow and round are both dominant traits and wrinkled and green are both recessive , all the offspring resulting from the mating were 100 yellow and round . The green color and the wrinkled pea shape had disappeared . However , these recessive traits reappeared in a ratio of three dominant to one recessive when two round yellow individuals from the dihybrid cross were mated . The green color and the wrinkled pea shape had not truly disappeared . In the second generation of the dihybrid cross , found that of the offspring were round and yellow , were wrinkled and yellow , were round and green , and were wrinkled and green . The results of these dihybrid crosses indicate that the two color and pea independently . The expression of one trait is not by the expression of the other trait . This is known as the law of independent assortment , which is second law of inheritance . There is nothing to dictate that round peas will be yellow or that wrinkled peas will be green . The alleles that code for different traits sort independently of one another during sex cell division ( meiosis ) Inheritance in Humans laws of inheritance also apply to humans . Indeed , the principles of segregation and independent assortment account for the transmission of certain human traits . Human blood type is one of the most familiar traits . Blood type has three , and on three alleles ofa single gene . Ifonly the A allele or both the A and alleles are present , the phenotype is Ifonly the allele or both the and alleles are present , the phenotype is . If both A and are present , the phenotype is AB . If neither A nor is present , the phenotype is . Note that is recessive to both A and , while A and are codominant . means that instead of one allele masking the other , the products of both alleles are observed . Additional examples of traits , or those controlled by a single gene , include Huntington disease , widow peak , cystic , sickle cell anemia , disease , hemophilia , and color blindness . or Online Inheritance in Man ( hosts an online database of almost human traits . It is important to note that the majority of human traits are not controlled by a single pair of genes . More often , a single gene can have multiple effects . Even more commonly , multiple genes are needed to produce a single effect . These are referred to as polygenic traits . Most human traits are polygenic , not . A good way of determining if a trait is polygenic is to assess whether the trait can be measured . Traits that can be measured , such as height or weight , are polygenic . Also , traits that have a wide range or lots of variability and can be affected by environmental factors are probably polygenic . The survival ofa species depends on genetic diversity and variation . If there is a reduction ofa gene pool due to geographic isolation or other environmental factors than a species is at risk of extinction .

Evolution in Action Post and Present LEARNING OUTCOMES By the end of this section , you will be able to Identify the major contributors to evolutionary theory and their theoretical contributions and historical context . Explain the theory of evolution and how it applies to the understanding of human origins . Identify the key differences between and . key evolutionary processes such as genetic drift , allopatric speciation , etc . Contemporary biological anthropologists utilize an evolutionary perspective . This means that the principles of evolution are used to understand how and why living organisms , including people , thrive in almost every environment on Earth . More , natural selection is accepted as the guiding force that shapes why living things are the way they are . Out of all the possible variations of beings competing for the same resources on Earth , those that prospered were the ones better suited to their environments than all other competitors . The principles of evolution and natural selection will be discussed in some detail in the next few sections , but it is important to establish at this early point that this chapter relies on the foundational assumption that natural forces are the only forces directing the development of life on Earth . Early Evolutionists and the Fixity of Species Evolution is as change in the allele frequency within a gene pool that can lead to changes in an organism morphology ( form and structure ) over time . Evolution involves the processes of mutation , natural selection , and speciation , which will be introduced in upcoming sections . Prior to the century , the prevailing idea in Western thought was that nature was and static it was made by a supreme being in the form it currently appeared , and it did not change . Within this natural system , living creatures were arranged within a set order that was considered to have been decreed by God , known as the great chain of being . This order featured God at the top , angels beneath God , and then humans . Below humans were various types of animals , followed by plants and minerals . This hierarchy was both because it placed some creatures above others and because it distinctly separated humans from the rest of the animal world . During a period stretching from the through the centuries , some people began to question whether the natural world was as static as it was traditionally perceived to be . The British scientist and architect Robert is remembered as the person in the Western world to claim not only that nature has changed over time but also that evidence of these changes remain . He hypothesized that fossils are the remains of actual and animals that were once alive . This conclusion was contrary to the previously accepted conclusion that fossils were nothing more than stone images . also noted that many marine fossils were located far away from any existing ocean , and he came to the then radical conclusion that Earth geography and physical had experienced dramatic changes . The person to propose a mechanism by which species could change was French naturalist , best known for having developed the theory of macroevolution , a hypothesis about how the actual transformation from one species into another species could occur . theory relied on the now defunct idea of the inheritance of acquired characteristics . argued that the usefulness ofa trait or organ could be ascertained based on its complexity or size . In , he believed that the usefulness of an organ could be judged by its size and the usefulness ofa trait by its complexity . He speculated that organs and traits that help a creature to survive will become bigger and more complex over time , while those that are of little use will become smaller and simpler and eventually disappear . His classic example of this theory in action is the long neck of a giraffe . speculated that as giraffes stretched their necks to reach the leaves at the tops of trees , their necks would grow longer , and furthermore , these longer necks would be inherited by the subsequent generations . This theory of the inheritance of acquired characteristics is also known as inheritance . One of the interesting things about theory is that he believed that wishes , desires , wills , and needs were all to motivate change . That is , wishing for or desiring a change in ones physical characteristics could make that change happen .

There are two primary problems with inheritance . First , desires , wishes , and needs do not change physical characteristics without a deliberate change in behavior . Someone may wish for blue hair , but their hair color will not change without dye . The second problem is that the inheritance of acquired traits is not possible . If someone dyed their hair blue , their children would not inherit blue hair . Traits that are acquired during a lifespan are not passed onto subsequent generations . Just because theory of macroevolution is not correct does not mean that it is . recognized the importance of interactions between organisms and their environments in the evolutionary process and was the to propose a mechanism by which evolutionary change from one species into another could actually occur . Georges , another Frenchman and a leading scientist in the early century , made numerous contributions to evolutionary thinking . He is best known for his theory of catastrophism , which he developed to explain the increasing number of fossils that were being found , some displaying impressions of creatures no longer found anywhere on Earth . Catastrophism proposes that , earthquakes , and other natural within the theory as acts of been responsible for killing all the animals alive in certain places at certain times . According to , either new animals have been created or the areas had been by animals from neighboring areas . To be consistent with emerging fossil evidence indicating that organisms had become more complex over time , proposed that new organisms with a more modern appearance were the result ofa more recent creation event . While scientists no longer adhere to catastrophism as a viable theory , idea of extinction continues to be an important component of evolutionary thinking today . Another major contributor to evolutionary thinking was Scottish geologist Charles , known as the father of modern geology . He wrote a treatise , Principles ( in which he argued that contemporary geological processes were the same as those that occurred in the past . These processes , such as wind and rain , produced the contemporary geological landscape . Mountains , lakes , and rivers were all created by these geological processes , many of them slow moving . This theory has come to be known as the principle of uniformitarianism . suggested that in order for such forces to produce momentous change , Earth must be much older than previously suspected . Prior to publication , the majority of natural historians believed that the earth was less than years old , a number arrived at through calculations made based on the Old Testament . By altering the suspected age of the earth from several thousand years to millions of years , changed the framework within which scientists viewed the geological past . Charles Darwin Role in Changing Views of the Natural World Charles Darwin introduced a new way of seeing the world that was both highly criticized and acclaimed in the community of his time . In spite of resistance by various segments of society , his theories of natural selection became the foundation of biological science . New knowledge pertaining to genetics and molecular science has strengthened Darwin theories rather than weakened them . Darwin the Apprentice When he was 17 years old , well before he gained a reputation as a naturalist , scholar , and scientist , Darwin was studying to be a medical doctor at the University of Edinburgh . Like many young people , he began to question his original choice of studies , and he decided to instead learn taxidermy under John . John was born enslaved and grew up on a plantation owned by a Scottish politician in what is now in South America . Charles , the of the plantation owner and a renowned naturalist , would visit the plantation often . He started inviting to accompany him on his frequent travels into the rainforest . On his travels , gained considerable knowledge about the and fauna America along with impressive taxidermy skills . After gaining his freedom in 1817 , John taught taxidermy at the University of Edinburgh , where he served as a mentor to Darwin over a period of several months . It is believed that Darwin relationship with may have his abolitionist views , which were later strengthened by accounts of slavery while Darwin was on his infamous voyage to the Islands off the coast of Ecuador .

110 Biological Evolution and Early Human Evidence FIGURE At the University of , John taught Darwin how to preserve birds . This is an example of , the great , collected by Charles Darwin in in May of 1833 . credit , Great , skin . Syntype . 19600 by Michelle Museums Victoria , BY 40 ) Darwin the Explorer and Scholar Charles Darwin left the University of Edinburgh and decided to pursue theology at Christ College , Cambridge . His studies there led to his appointment in 1831 as a naturalist on the Beagle for a expedition around the world . During this voyage , Darwin collected , dissected , and organized various specimens , especially in the Islands , a chain of islands off the western coast America . His observations in the marked a crucial point in his thinking on evolution . He noted that the fauna and of the western coast of South America were similar to those he observed in the , but still distinct enough to be considered different species . More surprisingly , the animals of the various islands in the chain differed slightly from one another . Darwin observed 13 different types of throughout 13 different small islands . The birds on each island differed in the structure of their beaks , their body form , and the color of their feathers . Each species was adapted to the habitats on each of the islands . Darwin used the techniques that taught him to preserve the , which became key pieces of evidence supporting Darwin theory of natural selection . Access for free at

FIGURE Charles Darwin is acknowledged as the father of the theory of natural selection . His work built upon the ideas of many other thinkers . His great contribution was in synthesizing these ideas into a coherent theory explaining the diversity of life on earth and the great changes in life over geological time . credit , Cambridge Philosophical Society , Cambridge University Commons , Public Domain ) During his travels on the Beagle , Darwin had been thinking about selective breeding of animals to produce traits that humans useful , commonly associated with the process of domestication . Darwin understood that selection provided important clues about the natural evolution of species . While on board the Beagle , Darwin read a book by English economist Thomas Robert titled An Essay on the Principle ( 1798 ) Darwin obtained two important points from this book . The was that human populations , if unrestrained , will grow exponentially . This means that they will double each generation . The second point was that food resources increase much more slowly than population does . noted that the growth of human populations is kept in check by a limit of food resources , which creates a struggle for existence . The struggle for existence is notjust about getting enough food but also about survival . In other words , it is about an individual ability to both enough food and not become another organism food . This simple concept , the struggle for existence , provided Darwin with a mechanism for how evolution could occur . Darwin realized that individuals with favorable characteristics for living in an environment are the ones that will survive to the age at which they reproduce , while those with less favorable variations will not . This mechanism for selecting for certain traits and features is known as the theory of natural selection . Darwin concluded from his observations that when a group of animals of the same species are geologically separated , they develop into separate species . This evolutionary process is commonly referred to as allopatric ( or geographic speciation ) and is based on the principles that related species share a common ancestor and that species change over time . Darwin did not originate the idea of evolution . Many of the ideas used by Darwin in his theory of natural selection were developed by other thinkers . Darwin was also not the only person thinking about natural selection . Another British natural historian , Alfred Russel Wallace , developed the same idea at roughly the same time , entirely independently of Darwin . Whereas Darwin developed his ideas based on his travels to the , Wallace thinking was by his own travels through the Archipelago between

112 Biological Evolution and Early Human Evidence and Australia . Wallace outlined his theory of evolution by natural selection in a letter written to Darwin while he was in Malaysia . As Darwin had not yet published his own work , Wallace and Darwin jointly presented papers introducing the theory of natural selection . In 1859 , Darwin published his book On the Origin of Species , some 20 years after his voyage on the Beagle . Understanding Darwin Theory of Natural Selection The theory of natural selection has main components . All organisms are capable offspring faster than the food supply increases . All organisms show variation . There is a struggle for existence , and those with the most suitable variations are most likely to survive and reproduce . Variations , or traits , are passed on to offspring ( inherited ) Small changes in every generation lead to major changes over long periods of time . A popular but concept related to natural selection is the term survival of the . Survival of the does not necessarily mean that the biggest and fastest survive instead , it refers to those who are most . This means that an organism has traits that are for survival and will be passed on to future generations . The term survival of the not even introduced by Darwin rather , it was used by English philosopher , anthropologist , and sociologist Herbert Spencer , who promoted the now discredited ideology of social . Social applied the concept of Darwin biological evolution to human societies , proposing that human culture was progressing toward the perfect human . Spencer writings became integrally related to the rise of racism and European colonialism . FIGURE This peppered moth is well camouflaged on the trunk of this tree . A darker colored moth would more easily be seen and eaten and would thus be less likely to pass on its genes to offspring . Natural selection relies upon the ability of natural variations to increase an individual chances of reproduction . credit Ben Commons , BY ) Examples of Darwin theory of natural selection can be found throughout the natural world . Perhaps one of the best known is the color change observed in peppered moths in England during the century . Before the Industrial Revolution , peppered moths in England were a light grey color , well on tree branches and less likely to be eaten by birds . Occasionally , through the process of mutation , black moths would appear in the population , but these were usually quickly eaten because they were more visible against bark . When soot from coal factories began to cover the bark of the trees , the black moths became better and the white moths were now more visible . Consequently , the black moths were the ones to survive to reproduce , while the white ones were eaten . In a few decades , all the peppered moths in the cities Access for free ot

were black . The process was termed industrial melanism . As coal usage decreased and the bark of the trees once again became lighter in color , white moths again dominated the urban areas . Examples of natural selection in modern times are numerous . Pesticide resistance in insects is a classic example . Pesticide resistance refers to the decreasing susceptibility of a pest population to a pesticide that previously was effective at controlling it . Pest species evolve pesticide resistance via natural selection , with the most resistant individuals surviving to pass on their ability to resist the pesticide to their offspring . Another good example is the rise of , bacteria that have become increasingly resistant to antibiotics . The Processes of Evolution Mutation is the creative force of evolution and represents the first stage of the evolutionary process . Mutation is as an alteration in a genetic sequence that results in a variant form . For a mutation to have evolutionary , it must occur in the sex cells ( sperm and ova ) This is because only genetic information that is in the sex cells is passed on from generation to generation . Mutations in chromosomes will not be passed on from one generation to the next . Whereas other evolutionary forces can modify existing genetic material , only mutation can produce new genetic material . One of the most interesting things about mutations is the fact that they are random . There is no way when a mutation will occur all scientists can do is estimate the probability of a mutation occurring . Mutations do not necessarily appear when they are needed . The conventional view is that mutations are harmful , but this is not always true . Some mutations are harmful , some are advantageous , and some are neutral . Advantageous mutations lead to changes that improve an individual survival chances of reproduction . The mutation that confers resistance to insecticide in mosquitos led to changes that improved their survival . Likewise , the mutation for black coloration in peppered moths led to increased survival during the Industrial Revolution . Neutral mutations have no effect on survival or reproduction . And some mutations are in fact quite harmful and do negatively affect certain individuals survival and reproduction . Mutations generally occur spontaneously in response to conditions in the body or in the environment . The exact cause of a mutation can not usually be determined , and the rate of mutation is very to determine . This is because mutations that are neutral or do not lead to obvious changes often go unnoticed . The probability of a mutation at any given gene is between in and in . While the probability that a point in an individual genetic material will have a mutation is clearly very low , the probability that the totality of an individual genetic material will have at least one mutation is much higher . The point is that while rare , mutation is also common . For example , although many mosquitoes have adapted to insecticides through a mutation that confers some resistance to the chemicals , if the mutation had not already been present in the population , the mosquitoes would have died out . The need for a mutation had no effect on whether the mutation appeared or not . There is currently a controversial pilot program in Florida aimed at dealing with mosquitoes against which insecticide sprays have increasingly become ineffective . The genetically mosquitoes were released in the Florida Keys in May of 2021 . The genetically altered mosquitoes produce female offspring that die in the larval stage , preventing them from growing to adulthood , in which they can then bite and spread disease . Genetic science currently has the power to use mutations to control or even wipe out an entire species . Genetic engineering has the potential to humanity , but it will undoubtedly also raise ethical questions and controversy .

How Insects Carry Genetic Time Bomb ) Genetically Genetically genes are introduced mosquitoes breed with into mosquitoes . the wild population . 55 it Mosquito population gene Larvae with the is greatly reduced . activates , killing gene mingle with the larvae . larvae . FIGURE Genetically mosquitoes are currently being bred that will die in the larval stage , thus greatly reducing the mosquito population . attribution Rice University , under BY license ) Genetic Drift Genetic drift is as the effect of random chance on a population , notably the way in which it determines whether an individual survives and reproduces or dies . Imagine that you stick your hand into a bucket with Halloween candy . What is the probability you will withdraw a Snickers bar ?

The composition candy in your bucket will be affected by the proportion ofpeople handing out Snickers bars compared to other candy . If each bucket of Halloween candy were a population , then one could say that genetic affecting the composition of the candy in your Halloween bucket . An important point about genetic drift is that it is directly and inversely related to population size . The smaller the population , the larger the of genetic drift the larger the population , the smaller the of genetic drift . In a large population , say , removing a couple of individuals will have a truly miniscule effect on the population . Note that in early human evolution , however , population sizes were small , so the effect of genetic drift may have been substantial . Gene Flow Gene is another important evolutionary force , involving the exchange of genetic material between populations and geographic regions . Without gene , there would be no without diversity , a species is at higher risk of extinction . Gene can be seen in the process of pollination , in which bees or carry and transfer pollen from one area to another . Anytime a gene is introduced to a new population where it did not exist before , that is gene flow .

FIGURE The process of pollination is a good example of gene flow . In this case , bees and butterflies transfer genetic material , in the form of pollen , from one flower to another . credit Honey Bee on a Dandelion , Sandy , by , BY ) Speciation is the rise ofa new species in response to an environmental change or pressure . Allopatric speciation , mentioned previously , is the most common form of speciation event . During allopatric speciation , a species when two populations become isolated from one another and continue to evolve . This isolation is created by geographic barriers such as mountains , rivers , or oceans . A good example of allopatric speciation is the different species of squirrel found on the two sides of the Grand Canyon . Descended from a common ancestor , the squirrels became reproductively isolated from one another by the Grand Canyon , eventually resulting in different species . FIGURE An example of allopatric speciation is the different species of squirrels that inhabit the Grand Canyon . The squirrel on the left is a Harris antelope squirrel and the one on the right is a antelope squirrel . They look similar but are different species . credit left , Harris Antelope Squirrel by Saguaro National , BY right , Antelope Squirrel by Renee , BY ) Sympatric speciation involves species that are descended from a common ancestor and remain in one location without a geographic barrier . A good example is the East African cichlid fish , which experience reproduction isolation due not to a physical barrier but to females selection of mates with certain coloration . The amount of light that reaches different levels and depths of the lake impacts how colors in the males appear to the females . The East African cichlid are also a good example of adaptive radiation . Adaptive radiation is seen when one or more species give rise to many new species in a relatively short time . Research shows that an explosion of about 250 very diverse species of in Lake occurred in less than 10 million

116 Biological Evolution and Human Evidence years ( and 2011 ) Other research suggests that the common ancestor was the result ofa hybrid swarm from two different locations , as seen in Figure . Meier et al . 2017 ) um , aw . EN ! i Am . su . mi cries um Africa En . FIGURE There are more than 250 different species of East African cichlid , all traceable to two common ancestors . The process through which a great number of species arises from a common ancestor within a relatively short period of time is known as adaptive radiation . credit by Phylogeny , BY ) In speciation , members of the same population are separated and over time evolve as separate species . Ring speciation is considered by some to be a type of speciation . Ring speciation occurs when several species coexist for a time in a region near one end of a geographic barrier . When part of the population migrates away from the original population ( or gene pool ) to the other side of the barrier , reproductive isolation results . Reproductive isolation is strongest for that part of the population that is farthest away from the original population . When too much variation has occurred between two groups , they will no longer interbreed , and as a result , development of two separate occur . While fairly rare , ring speciation is believed to explain the different species of the California salamander genus . Access for free ( it

I I I I , I 200 FIGURE This map shows the range of different species of the California salamander genus , believed to have developed through the process of ring speciation . In ring speciation , reproductive isolation leads to the development of new species from a common ancestor , due to separation caused by distance a physical barrier . credit Thomas , Stuart , and Craig Commons , BY ) Evolution Biological anthropologists are interested not only in how a species is best but also in how often and by what means new species are developed . The traditional view of evolution assumes that morphological , behavioral , and genetic changes occur gradually and accumulate in a single unbroken and unbranching line this view of evolution is known as gradualism . If this perspective is correct , scientists would expect to numerous fossils exhibiting evidence that they are slowly and gradually transitioning into new and distinct species . However , while fossils are rare , fossils showing evidence of transitional forms are even rarer . While the dearth of transitional fossils is often attributed to the incompleteness of the fossil record , it has caused some biological anthropologists to question if evolution is truly gradual . What can be observed in the fossil record are static populations that are interrupted by sudden bursts of change . This phenomenon of long periods of stasis , or no change , followed by quick periods of change is known as punctuated equilibrium . Instead of a gradual accumulation of small changes , punctuated equilibrium suggests that rapid changes due to a variety of environmental factors , including climate change , are characteristic of the formation of new species . The fossil data for a large number of organisms periods of stasis followed by rapid and massive change . The scarcity of intermediary forms in the fossil record has led some to conclude that punctuated equilibrium is the dominant theory . However , the fact that intermediary forms do exist suggests that gradualism is also an important factor in the evolution process . One research study found that 30 to 35 percent of speciation events occurred as the result ofa sudden event or change , while the remainder showed evidence of gradualism ( Phillips 2006 ) In both the gradual and punctuated models , speciation takes the form of branches through time rather than a linear progression . Evolution is neither linear nor progressive , but rather a branching tree of life containing both areas of divergence and points of a shared common ancestry .

118 Biological Evolution and Early Human Evidence The Tree of Life Showing Evolutionary Relationships FIGURE This sketch made by Charles Darwin illustrates his attempts to think through the branches of evolutionary relationships . credit Charles Commons , Public Domain ) During Darwin time , evolutionary relationships had to be determined largely by structural and physical characteristics . Molecular science had not yet been developed . The binomial nomenclature discussed earlier not only allowed distinction between species but also provided clues to evolutionary relationships . For example , which of the below species of would be the most distantly related ?

Dana us Dana us Dana us The answer , of course , would be , the viceroy , which is a mimic of the monarch ( The part of the viceroy name , is the genus . The fact that it is different from the others shows that it is more distantly related . this image are examples of two different species , one a monarch and the other a Viceroy butterfly . What differences can you see ?

credit left , Today Mass Extinction and Thermal Maximum by , Public Domain right , A Viceroy Butterfly by Benny , BY ) It is important to note that the system has limits . Sometimes , species can be to identify by physical characteristics alone . Species that exhibit mimicry and larval forms in different stages of Access for free at

development can take on the appearance of other organisms , resulting in errors in . Can you tell which of the in Figure is the monarch ?

Close examination reveals that the markings on the wings are a bit different . The monarch is on the left , and the monarch mimic , the viceroy , is on the right . Likewise , in Figure , you can see how it might be to correctly classify barnacles , crabs , and based on physical appearances . One may be tempted to classify the barnacle and the limpet as being closely related due to the conical shells that they share , when in actuality , the barnacle is more closely related to the crab , as they are both crustaceans . The conical shells of the barnacle and the limpet are similar adaptations in response to similar environmental pressures , not evidence that they are closely related or share a common ancestor . There are limitations in the of organisms based on physical appearances alone . Crabs ( crustacean ) The shells of and barnacles , while similar , do not mean they are closely related . are actually aquatic snails , while barnacles are more like shrimps , which makes them more closely related to crabs . gastropod ) FIGURE Classifying species based on physical similarities alone can lead to false conclusions . Although barnacles and look much more like one another than they do the crab on the left , barnacles are actually more closely related to the crab . credit left , by Sally , BY top right , Barnacles by Mo , BY bottom right , Limpet Family at Sunny Cove by Tim , BY ) Structural as Evidence of Relationship Structural similarities may be derived traits ( homologous structures ) inherited from a common ancestor , or they may have developed independently ( analogous structures ) An example of a homologous structure is the grasping hand found in both humans and chimpanzees , which suggests that humans and chimpanzees share a common ancestor that also had a grasping hand . Analogous structures are seen in the wing ofa and the wing of a bat . While both wings serve a similar function , these two organisms likely developed their wings independently and do not necessarily share a common ancestor . Identifying is essential for creating hierarchies of phylogenetic relationships because homology indicates that shared features are due to common descent . However , can be to identify in nature , and they are easy to confuse with analogous traits .

Human Dug Bird Whale FIGURE The structural similarities visible in these various species are homologous , meaning that the similarities are the result of these animals common ancestor . attribution Rice University , under BY license ) or the use of , is a method of visually distinguishing between homologous ancestral and derived characteristics . Ancestral characteristics are found in the common ancestor of the species being , whereas derived characteristics are only found in the groups in question . An ancestral characteristic that humans share with common ancestors is opposable thumbs . In contrast , a derived trait that is only found in modern humans is the chin . By exclusively looking at derived characteristics , biological anthropologists can develop a clearer understanding of the relationships between the groups being studied . The Molecular Tree of Life and The emergence of genetic and molecular science has provided additional tools and lines of evidence to verify evolutionary relationships . The phylogenetic tree is a model used by modern to reveal the complexity and diversity of life and its many branches . Phylogenetic trees show how species and other taxon groups evolved from a series of common ancestors . They are based on both physical and genetic evidence . FIGURE Phylogenetic trees illustrate how old species are believed to be and their degree relatedness to one another . This particular tree pertains to primate species . credit Commons , Public Domain )

What Is a Primate ?

LEARNING OUTCOMES By the end of this section , you will be able to primate . Describe the relationship between primate behavior and environment . Identify and classify the key taxonomic groups of primates . What Is a Primate ?

FIGURE Orangutans , the only great ape from Asia , are one of many living primate species . Others include lemurs , monkeys , gibbons , and human beings . credit Dawn Commons , Public Domain ) human characterized by a number of distinct physical features that distinguish them from other mammals . These include opposable thumbs and ( in nonhuman primates ) opposable big toes the presence of digits ( or toes ) on the appendages nails instead of curved claws pads at the tips of the made up of deposits of fat and nerves reduced reliance on sense of smell and a relatively small snout depth perception binocular vision ( being able to see one image with both eyes ) a relatively slow reproductive rate relatively large brain size and postorbital bars ( bony rings that completely surround the eyes )

FIGURE The hands of this bonobo , including its opposable thumbs , look very similar to human hands . Opposable thumbs or toes are a primate trait shared by no other group of mammals . credit Bonobo by Marie van , BY ) The four traits enhance dexterity and enable primates to use their hands and feet differently from other mammals . Other traits on this list represent a shift in emphasis among the sense organs between primates and other mammals . Primates are characterized by a greater emphasis on vision and a reduced reliance on smell relative to other mammals . Primate Behavioral Variation Anthropologists regularly ask , What makes us human ?

Comparative studies of humans with nonhuman primates help answer this question . Comparing the behavior of nonhuman primates and the behavior of human beings helps anthropologists identify what culture is and develop operational for it . Without the comparative perspective provided by , anthropologists would be missing an important piece of the puzzle of what makes humans human . Without , anthropologists would not be able to fully understand humankind . Studying nonhuman primates in their environment is key to understanding variations in behavior and can shed light on humanity ancient past . are studying the chimpanzees at National Park in , where they live in the rainforest . The behavior of chimpanzees that live in the tropical regions of Africa is quite different from the behavior of chimpanzees that live in the savanna at in , in West Africa . chimps hunt red colobus monkeys without the use of tools , just catching them with their hands , while the chimpanzees hunt ( also known as bush babies ) using sticks that they adapt and used as spears ( et al , 2015 ) The two environments also show differences in gender roles with both males and females in the savannah group involved in hunting while only male chimpanzees hunt in the rainforests . Studying how these nonhuman primates both make and use tools is critical for understanding how humans fossil ancestors may have used and constructed tools . An important question that and biological anthropologists seek to answer is the question , do nonhuman primates have culture ?

Whenever we see an exchange of ideas where one individual is involved in teaching another and when that knowledge is passed on to others in a group is according to anthropologists , a What a Primate ?

form of culture . We see this happen in chimpanzee groups where older chimpanzees teach the young how to use sticks to , the process of extracting termites from a termite mound using a stick . FIGURE This chimpanzee lives in the National Park in . Chimps living in rainforest environment have developed a very different set of hunting techniques and tool use from their relatives living in the grassy savannah . credit Chimp Eden Sanctuary Mimi by , BY ) Explaining Primate Success Why primates evolved as they did and how they and exploited the range of ecological niches they now are questions that have not yet been adequately addressed . Over the last century , various hypotheses have been raised to account for the evolution of primates and their unusual anatomical characteristics . These theories include the arboreal theory , the visual predation hypothesis , and the angiosperm theory . The arboreal theory proposes that primates evolved the traits they did as an adaptation to life in the trees . primates evolved thumbs and big toes that are perpendicular to the other digits to help them grasp onto branches . Matt , a professor of anthropology at Boston University who spent his career trying to understand why primates evolved the way they did , has complicated this theory . recognized that eyes are characteristic not only of primates but also of predators such as cats and owls that prey on small animals . Thus , eyes , grasping hands and feet , and the presence of nails instead of claws may not have arisen as adaptations to an arboreal environment . Rather , they may be adaptations that helped early primates succeed as predators . According to the visual predation hypothesis , primate features are adaptations for hunting insects and other small prey in the shrubby forest undergrowth and the lowest tiers of the forest canopy . The angiosperm theory states that the basic primate traits developed in with the rise of plants , also known as . Flowering plants provide numerous resources , including nectar , seeds , and fruits , and their appearance and were accompanied by the appearance of ancestral forms of major groups of modern birds and mammals . Some argue that visual predation is not common among modern primates and that eyes and grasping extremities may have arisen in response to the need for visual and tactile discrimination in order to feed on small food items , such as fruits , berries , and seeds , found among the branches and stems of plants . Primate and Taxonomy Scientists generally classify the order Primates into two ( and ( and ) The or The are considered to be primitive primates that evolved much earlier than other primates . This 123

suborder includes lemurs and . All the primates , or , possess numerous anatomical traits that distinguish them from the primates , or . These include a nail on the second toe , referred to as a grooming claw , and incisors in the that are tightly packed together and protrude from the mouth , forming what is called a toothcomb . There are seven families of living , and all of them are found in what anthropologists refer to as the Old World , which consists of the continents of Africa , Asia , and Europe . Five groups of living are found only on the island of Madagascar off the coast of Africa . Two additional families are found in Africa and Asia . FIGURE The pygmy slow loris ( is an example of a primate . Pygmy slow be found in Vietnam , and a province of China . credit Lionel Commons , Public Domain ) The or The are broken down into two further , and , and the are further divided into and . The , or , are exclusively found in the New World ( Central and South America ) and are colloquially referred to as New World monkeys . Their name is derived from the rounded shape of their external nostrils , which open off to the sides . New World monkeys are also distinguishable by their prehensile tails that serves as an extra limb for extra support when moving in the trees . The , or , are found throughout Africa and Asia . They differ from the New World primates in that they possess narrow nostrils that face downward . The contain two , and , and are exclusively Old World . The contain two main groups cheek pouch monkeys ( and monkeys ( The most distinctive feature of the cercopithecoid primates is their molars , which exhibit two parallel ridges . The most distinguishing feature of the is that they do not have tails and are largely terrestrial , or . Examples of include gibbons , chimpanzees , gorillas , orangutans , and humans . The Puzzle The tarsier , which belongs to the family , has both prosimian and anthropoid characteristics , which has made it for scientists to classify . are currently within their own under the . One of the characteristics that share with other , including humans ) is the inability to manufacture their own Vitamin They are the smallest known primate and are nocturnal , with extremely large eyes that take up much of the space in their skull . Due to their size of the eyes , the tarsier can not rotate them instead , it can rotate its head 360 degrees like an owl . are also the only primate carnivore , eating largely insects and sometimes small animals like bats and lizards . do not do well in captivity . They are extremely sensitive to noise and can become easily stressed . In fact , they can

become so stressed that they die by suicide by banging their heads against tree trunks . FIGURE The Philippine tarsier ( Carlito ) is found only in the southern portion of the Philippine islands . The tarsier has been challenging for scientists to classify , exhibiting both prosimian and anthropoid characteristics . credit Tarsier Monkey by Jacky , BY ) Origin of and of Primates LEARNING OUTCOMES By the end of this section , you will be able to Explain the concept of deep time . fossils and explain some dating methods used on fossils . Identify some of the key characteristics of early primate fossils , including their respective time periods . Understanding Concepts of Time Geologists divide deep history into time periods known as eras . Eras are generally based on the fossil life forms observed . The oldest of the geological eras is the , which began approximately four billion years ago . The majority of the fossil evidence that we have for primate evolution comes from the current geological era , dating from 65 million year ago ( to the present . The era is divided into a series of . Each epoch is associated with forms that evolved during that time period . Fossils and Dating Methods Biological anthropologists primarily , although not exclusively , study fossil artifacts . A fossil is any remainder ofa plant or animal that has been preserved in the earth . Upon the death of an organism , its body slowly decomposes until all that remains are the teeth and the bones or a mere impression of the organism original form . Under most conditions , teeth and bones and impressions eventually deteriorate , too . However , occasionally conditions are favorable for preservation . Examples of favorable materials for fossil formation include volcanic ash , limestone , and groundwater . Scientists do not have fossils of everything that lived in the past , and in some cases , remains from only a few individuals of a species have been found . The fossil record is very incomplete . Robert Martin , a curator at the Field Museum of Natural History in Chicago ,

estimates that there have been more than primate species , while the remains of only percent have been found . Fossils are very rare , but they are extremely informative about human biological evolution . Making Sense of Fossils An important part fossils is determining how old they might be and putting them in chronological order . In order to use a primate fossil to reconstruct the evolutionary history of primates , anthropologists must be able to estimate approximately how old that fossil is . For some time , relative dating methods were the only methods available for dating fossils . Relative dating calculates the approximate age of a fossil in comparison to other fossil specimens . The last half century has seen important advances in absolute dating , including techniques that have made possible the dating of the earliest phases of primate evolution . Absolute dating calculates the actual biological age of a fossil in years within a range of years . Relative Dating Techniques Stratigraphy is the and most commonly used method of relative dating . Stratigraphy is based on the observation that soil is deposited in successive layers , or strata . The oldest layers of soil ( and any artifacts or fossils within them ) will appear beneath more recent layers of soil ( and any artifacts or fossils within them ) In addition to using the location of layers of soil to date fossils deposited within these layers , biological anthropologists also sometimes make use of other items consistently found in a layer of the soil . These items are referred to as indicator artifacts because they help indicate the relative age of fossils and other artifacts . The best indicator artifacts are those that have a wide geographic distribution , are presence for a short period of geological time , are from a species that underwent rapid evolutionary change . Different indicator artifacts have been used to ascertain relative age in different areas of the world . In Africa , elephants , pigs , and horses have been used to establish relative dates of different geological strata . The stratigraphy at Gorge in East Africa , for example , was established based on fossil pigs . The various species of pig in successive strata are different and distinct , allowing to distinguish the strata based on the pig species found within them . Once the stratigraphy of an area is established , the relative ages of two different fossils in different sites can be determined by the associated indicator artifacts . If a site has been disturbed , stratigraphy will not be a satisfactory way to determine relative age . In such a situation , it may be possible to use absolute dating methods to estimate the age of fossils found together in a disturbed site . Absolute Dating Techniques Many absolute dating methods are based on the rate of decay of a radioactive isotope . A radioactive isotope is a chemical element that dissipates excess energy by spontaneously emitting radiation . These emissions happen at known and stable rates . Once the rate of a radioactive isotope is established , the age of a specimen containing that isotope can be estimated within a range of possible error . 14 The method for determining the absolute age of fossils is or ( pronounced ) dating . All plants and animals contain the isotope ( Plants absorb from the air , and animals ingest plants containing the isotope . Because plants only absorb when they are alive and animals only consume plants when they are alive , scientists can determine how long ago an animal or plant died based on the amount of that remains in their cells . has a known of years . This means that approximately half of the original in an organism will be eliminated in years after its death . For example , if an organism had an original value of 100 , then after years , only 50 units of would be present . Thermoluminescence Another absolute dating technique that is frequently used by is thermoluminescence dating . Thermoluminescence dating requires that either the fossils to be dated or the sediments that the fossils are within have been exposed to a event , such as a volcanic explosion . During such a high temperature event , all the radioactive elements within the material are released . Consequently , the amount of

radioactive elements that have accumulated in the artifact since the time of the event can be used to calculate the artifact age . Primates of the Epoch The epoch began approximately 65 and ended about 54 . It is the most poorly understood epoch of the era , as it is the time period with the fewest fossils to represent it . However , this epoch is considered important to primate evolution because it offers the unequivocal record of the earliest primates . Evidence of the most primitive primate yet was found in the US . state of Montana , in a geological deposit that was dated to the earliest part of the . This creature is known as . is similar to extinct and living primates and distinct from other mammals in the presence of an elongated last lower molar and an enlarged upper central incisor ( resulting in what one could think of as Bugs Bunny teeth ) These two characteristics , which are shared by all living primates today , suggest that may be the common ancestor of later primates . unio Scale inches ( from head to tip of tail FIGURE unio may be the common ancestor of all later primate . Remains of unio have been found in deposits dated to be about 63 million years old . attribution Rice University , under BY license ) of the Epoch The epoch , which began approximately 54 and ended about 34 , is marked by the disappearance of and the appearance of primates that more closely resemble primates , especially in the fact that they possess postorbital bars composed entirely . A postorbital bar is a bony ring surrounding the entirety of the eye orbit . This contrasts with other mammals whose postorbital bars are part bone and part cartilage . Some fossil specimens also possess a toothcomb a grooming claw , characteristics that are exclusively found in primates today . Other anatomical characteristics that are significant would be the ankle bones which researchers believe played a key role in the evolutionary success of primates . The evolution during the was tremendous . It has been hypothesized that there were four times as many primates during the than there are living primates today . Fossil primates in deposits are common in North America and Europe and are becoming known in Asia and Africa . However , there are currently no known fossil primates from the in South America or Antarctica . of the Epoch The epoch , which began approximately 34 and ended about 22 , marks the appearance of the fossil monkeys . The earliest unambiguous fossils were found at the , an archaeological site about 60 miles from Cairo , Egypt , that today represents part of the Sahara . The primates are divided into two main groups and . Based on their teeth , these primates are believed to be the earliest New World and Old World monkeys , respectively . Teeth are generally described according to a dental formula that indicates the number of each type of teeth in each quadrant of . An organism with a dental formula has two incisors , one canine , two , and three molars in each quadrant of their upper and . Based on the presence of a third premolar , a

trait found in all New World monkeys , it is probable that represents the earliest New World monkeys , even though they evolved in Africa . Likewise , it is probable the represent the earliest catarrhine primate , as they are the fossil monkeys that possess a dental formula of found in catarrhine primates . Apes The epoch contains fossil evidence of some of the earliest apes such as Proconsul which lived in Africa from 23 to 14 . The earliest ape , found in Africa , is Proconsul . Unlike apes , the Proconsul lacked long , curved digits , suggesting that they were able to hang from branches but more often moved about on all four of their limbs . Proconsul also lacked a tail , which is why they are considered apes and not monkeys . Like all Old World monkeys and apes , including humans , their teeth show a pattern of . Another ape from the is . fossils are very common throughout Asia , with a particularly large number having been found in Turkey . Like modern day humans , they exhibit very thick dental enamel , suggesting that these apes regularly ate very hard foods . The most intriguing aspect of morphology is that the skulls show a tremendous resemblance to the living orangutan in features such as its tall nasal openings and high eye sockets . FIGURE is one the earliest known ape species . Fossil remains exhibit the tall nasal openings and high eye sockets currently visible in orangutans . credit ( Fossil Ape ) Formation , Upper Plateau , Pakistan ) by James , BY ) While it is known that orangutans probably evolved from a ape , there are no clear candidates for the ancestors of modern African great apes . There have only been two fossils found that clearly and unequivocally belong to the ancestors of modern African apes . is a large late ape found in northern Kenya . It is known to resemble modern African apes . It differs from other fossils in having molar teeth that are elongated in a direction from the front of the mouth toward the back , instead of from cheek to tongue . Another fossil from the late ( that is sometimes as an ancestor of modern African apes is , found in Greece , which has facial morphology that links it to both African apes and humans .

Our Ancient Past The Earliest LEARNING OUTCOMES By the end of this section , you will be able to Compare and contrast some early species . Walking on Two Feet The term refers to all species considered to be Identify some key adaptations and characteristics found in early . Identify key adaptations and derived traits that emerged in changing environments . in direct lineage to humans , which include the genera Homo , and . Hominids refers to all modern and extinct great apes , which include humans , gorillas , chimpanzees , been understood to represent different things over the orangutans and their ancestors . These terms have ears , but the provided here are the most current . While all may differ in varying ways from one another , they all share one anatomical behavioral complex bipedal locomotion . Scientists can hypothesize about how a creature moved analyzing several aspects of its morphology . animals that move by swinging from branch to branch , generally have long arms , while , animals that propel their bodies through the force of the primates have arms and legs of equal length . In bipedal other is called the step leg . While the stance leg is on the ir lower limbs , have relatively long legs . Arboreal , one leg is called the stance leg , and the ground , the step leg is off the ground and striding forward . During normal walking , both feet are on the ground only about 25 percent of the time . As speed of locomotion increases , the percentage of time that both feet are on the ground decreases . As a result , for most of the time that bipedal organisms are moving , their is balanced on only one of their legs ( the stance leg ) To ensure that bipedal organisms do not fall over while balanced on their stance leg , they have undergone many anatomical changes since the earliest ancestors . One of the most important anatomical changes that successful is the angling of the femur ( upper leg bone ) inward at what is referred to as a valgus angle , which positions the knees and feet under the center of the pelvis . Bipedal have also evolved spinal curves that make it possible for the hips to balance the weight of the upper body . The evolution of the arch in the foot as well as the realignment of the big toe so that it is parallel to the other toes is also instrumental in transmitting weight during the step phase of bipedal locomotion .

130 Biological Evolution ond Human Evidence Valgus Angle The appearance of a valgus angle provides evidence of . Femoral head is angled . Femur is angled straight the Femur angles in toward knees in humans . FIGURE In humans , the femur bones angle inward . This adaptation , known as the valgus angle , makes bipedal locomotion ( walking upright ) more comfortable and more . attribution Rice University , under BY license ) The most important evidence of early is provided by the work of English paleoanthropologist Mary . In the , Mary discovered a trail of footprints made by three bipedal individuals who had crossed a thick bed of wet volcanic ash about . These footprints were found in East Africa at the site of . Based on the date and the location , it is probable that these footprints were made by . Analysis of the footprints indicates a modern striding gait . FIGURE These replicas of the footprints found in by Mary are on display at the National Museum of Nature and Science in Tokyo , Japan . credit Fossil Hominid Footprints ( Ma Area , Northern , Eastern Africa ) by James , BY ) The evolution of required complex anatomical reorganization . For natural selection to produce such a tremendous amount of change , the of these changes must have been great . There have been dozens for these changes , ranging from freeing hands to carry tools , food , or offspring to increasing energy efficiency or thermoregulation ( the ability to maintain the body temperature ) by exposing Access for free at

more of the body surface . None of the hypotheses are testable , making it truly challenging to understand why humanity ancestors made such a huge behavioral shift . The next sections explore some of the key discoveries of early fossils in which anthropologists see some of the earliest indications of the adaptation of in the human story . Hominids The hominid fossils appear in the late , 10 to . Sometime between and , hominids moved out of the trees and began to adapt more fully to a living niche . Unfortunately , the fossil evidence from this time period is extremely sparse , but new continue to be discovered . A complete cranium of was found in 2002 by French paleoanthropologist Michel Brunet and his team in Chad in West Africa . is a fossil ape that lived approximately and is claimed by some researchers to be the last common ancestor of humans and chimpanzees . Genetic studies indicate that humans and chimpanzees diverged from one another sometime between and , so this species lived right at the time of the divergence . The cranial capacity is a mere 350 cubic centimeters ( which is equivalent to a chimpanzee the modern human cranial capacity is approximately . also has a very large brow ridge ( the large bone above the eyes ) and the location of the magnum , the opening at the base of the skull where the spinal column enters the skull , suggests that its head was not held over its spine and thus it was not bipedal . was found in Kenya in 2001 by geologist Martin of the College de France and paleontologist Brigitte of France National Museum of Natural History . was dated to approximately . was proposed to be a due to anatomical traits that suggest . For example , the femoral head ( the big , rounded ball at the top of the leg bone that connects the leg to the hip ) is much larger than in quadrupedal apes , suggesting the femur was being used to support the weight of the upper body . The muscles attached to the femur also suggest bipedal movement . Another feature that suggests that is truly a is the teeth , which exhibit thick dental enamel and small , square molars , much like modern humans . The epoch extended from to . Fossils from the show evidence of the evolution of that are clearly bipedal . They also show evidence of clear , albeit primitive , cultural behavior . Climatically , the was colder than the preceding , which resulted in changing sea levels and an increase in ice at the poles , opening up some previously inaccessible areas . During this period , North and South America became connected through the Isthmus of Panama , and a land bridge across the Bering Strait appeared between Alaska and Siberia . was found in Ethiopia in 1992 by American paleoanthropologist Tim White and was dated to about . This is the discovered species to be dated to the era . Based on the forward position of the foramen magnum , it can be concluded that was bipedal . Also , the upper arm bones are very small , suggesting that the arms were not used to support weight during locomotion . possesses numerous traits , such as thin dental enamel , evidence ofa reduced canine , and an opposable big toe . As a result of the latter trait , many believe that was bipedal on the ground and quadrupedal in the trees . This hypothesis is supported by the fact that the fossil bones were found in relatively heavily forested environments . The reduced canine is a derived trait appearing even earlier than and is not what we would typically see in African ape males who have large intimidating canines . Current hypotheses suggest that over time smaller canines became dominant when there became less need to show aggression along with a female preference for males with milder temperaments ( et al . 2021 )

132 Biological Evolution Evidence FIGURE These skeletal remains have been as , the first species discovered that has been dated to the Era . credit Commons , BY 30 ) The Robust and The next few sections will examine various australopithecine species that had diverse physical characteristics related to morphology of the teeth and skull . Based on these characteristics , these species into gracile and robust forms , as illustrated in Figure . Gracile species had a more pronounced projection of the jaw ( prognathism ) less cheeks with no sagittal crest , and smaller teeth and jaws . The sagittal crest in the robust accommodated large jaw muscles for chewing tough plant materials . Robust australopithecine Gracile australopithecine Sagittal crest More pronounced projection of face ( prognathism ) FIGURE Australopithecine species are as either robust or gracile . A feature of the robust species is the sagittal crest visible on the on the left . Gracile species , such as , on the right , display more pronounced projection of the face ( prognathism ) credit left , Commons , Public Domain right , Fossil Hominid ( Eastern Africa ) by James , BY ) Species considered to be the gracile include , Access for free at

and . The robust ( under the genus ) include , and . The gracile species emerged around and disappeared , while robust species continued to exist for another million years . The next sections will first take a look at some of the gracile forms of australopithecine , followed by the robust forms . was the australopithecine discovered , in 1924 , and was described by Australian anatomist and anthropologist Raymond Dart , who found the fossil in a box of fossils sent to him by lime quarry workers at a site called in South Africa . The most notable specimen in the box was a skull from a child , which Dart had to chip away from the stone it was embedded in . It took Dart four years to separate the teeth . The skull is now known as the skull or child . Dart argued that the child represents an extinct race of apes intermediate between living and man ( Wayman 2011 ) He noted that the skull was long and narrow , not rounded as in modern humans , and its brain averaged a mere 422 , equivalent to a chimpanzee . However , the child did not possess brow ridges , had circular orbits , and had minimal prognathism as well as small canines and no diastema ( space in the jaw for large canines to be positioned when the mouth closes ) These latter traits are all analogous to modern humans . Most importantly , Dart noted that the forward position of the foramen magnum indicated that the skull was poised on top of the vertebral column , suggesting and an upright posture . FIGURE This partial skull is from a specimen known as the child . The species , displays traits that resemble modern humans in some ways but not others . credit Commons , Public Domain ) In 1973 , a good portion ofa skeleton ( about 40 percent ) was found in the Afar region of Ethiopia by American paleoanthropologist Donald . He called the skeleton Lucy , after a Beatles song . It was dated to around and was determined to be a member of the species . Like all fossils recently discovered , Lucy was given an identification or accession number , The acronym stands for the Kenya National Museum , where the fossil is housed , and AL stands for the Afar locality where the fossil was found . Since then , more specimens of this species have been found in Kenya , and Ethiopia , all in East Africa .

FIGURE This child stands next to a recreated skeleton of . The long arms and long , curved and toes of are apparent . credit Fossil Hominid ( Lucy Skeleton ) Formation , Ma Area , Afar Triangle , Northern Ethiopia , Eastern Africa ) by James St . BY ) is dated from to with an endocranial capacity of around 400 , which is approximately the same as a common chimpanzee . There are two morphological features that provide evidence that moved more like a great ape than a human . First , it had arms that were substantially longer than modern humans . Long arms are generally found in animals that hang from branches , suggesting that also exhibited this behavior . Also , possesses and toe bones that are long and curved , another characteristic of animals that hang from branches . However , there is one important morphological feature ofA . that suggests that this species may have moved somewhat like modern humans . The shape ofA . pelvis ( hip bones ) looks substantially more like a modern human than it does an ape . Instead of the hip bones being long and narrow , they are short and wide . Most believe that this change in pelvic shape indicates that moved like modern humans do , on two legs . While may have , the morphological differences between and modern humans suggest they did not move in exactly the same way . Current consensus is that was both tree dwelling and bipedal . Other anatomical evidence includes a more anterior position of the foramen magnum and the angle of the femoral head and neck . Also found in Ethiopia , is dated to approximately . Its cranial capacity is slightly greater than , at 450 . has incisors that are larger than those of any of the known or Homo . The function of the large incisors is not yet known . The most exciting aspect ofA . is that it provides evidence of the earliest use of stone tools by a . fossils were found with fossil bones of , such as antelopes , that displayed numerous cut marks . Cut marks are made on bones by the process of removing meat from the bones with stone or metal tools . Based on this , biological anthropologists have hypothesized that used some type of stone tool for butchering .

In 2008 , the clavicle bone was discovered by Matthew Berger , the son of American paleontologist Lee Berger , in , South Africa . Further excavation in a cave feature uncovered two partial skeletons , one of an adult female and the other a . is considered an important species because it appears in the fossil record around the time of the first emergence of the genus Homo around . The ofA . was initially to determine , due to its complex overlapping features , which include humanlike spine , pelvis , hands , and teeth and a foot . This combination of traits suggests both tree climbing and bipedal adaptations . After studying the characteristics collectively , anthropologists as a species . It is considered a direct ancestor of Homo erectus and Homo , which are discussed in Chapter , The Genus Homo and the Emergence of Us . It is believed that could be a descendent of , which suggests the species may be a dead end within the lineage to humans . Its and relationship with the genus likely remain highly debated . FIGURE These bones are from , which displays a humanlike spine and pelvis but a foot . credit Commons , BY ) Thirteen years after Raymond Dart discovery , South African paleontologist and medical doctor Robert Broom discovered at a site called in South Africa . The most obvious difference between Dart and Broom respective fossils , and ! is that the morphology fossil is much larger . Its features include a sagittal crest and a zygomatic arch for the attachment ofa large muscle for chewing a diet reliant on hard nuts and seeds . This interpretation was further supported by scanning electron microscopy ( SEM ) which was used to evaluate the markings etched into the teeth . As the teeth increased in size the incisors and canines shrank , giving a face with less projection of the jaw . There are some who argue that depending on the environment and locale , some may have been , with varied diets similar to those of . and van der 2000 ) Following in Broom footsteps , other scientists began searching for fossils in East Africa . Beginning in 1931 , and British paleoanthropologist Louis and his wife , Mary , worked in what is known as the Eastern Rift Valley , which is a trough extending through Ethiopia , Kenya , and . They searched for almost 30 years before they found their first fossil , as 1959 . It is often referred to as the because of its mohawk of bone on the top of the skull . Other features include a low or absent forehead , a face , large jaws , and large attachment sites over the entire skull for chewing muscles .

We have little knowledge about ( shown in Figure , which has been dated to about and is referred to as the black It is believed that this species falls somewhere between the robust and gracile , having characteristics of both . The species was discovered in Ethiopia in 1967 by a French expedition team headed by Camille and Yves . FIGURE Much remains to be learned about , which has characteristics of both the robust and gracile . credit ( Fossil Hominid ) Formation , Upper , Ma , Lake Area , Kenya ) by James , BY ) Landmarks and Questions While the fossils discovered up to this point have provided a small window into the story of humanity past , they have also simultaneously raised numerous questions . Questions related to phylogenetic relationships and points of divergence are challenges for , who have only fragmentary fossil evidence to build hypotheses around . Nevertheless , the discoveries that have been made represent important landmarks in anthropologists understanding , providing clues that will lead to the next steps in the human journey . ACTIVITY Pedestrian Survey Conduct a pedestrian survey to try to locate fossils near where you live ( trilobites in New York , ammonites in Texas , shark teeth near , arrowheads ) Think about where you would most likely a fossil and why . Try to extract one without destroying the environment around it , which provides important context . Try to out what kind of fossil it is by doing some Internet research . Why do you think that this fossil was preserved ?

What information would make the search for fossils easier ?

Key Terms allele an alternative form of a gene that arises by mutation and is found in the same place on a chromosome , directly impacting the expression of a genetic trait or phenotype . allopatric speciation speciation that occurs when two populations of the same species become isolated from each other due to a change in the environment , such as geographic isolation . analogous structures anatomical similarities between two species that suggest not a common ancestor but rather similar environmental adaptations . ancestral characteristics homologous structures or traits that may also be found in the common ancestor of the species being . angiosperm theory a hypothesis that suggests that primate origins and typical primate characteristics developed in response to the emergence of plants . arboreal theory a hypothesis that proposes that primates evolved the traits they did as an adaptation to life in the trees . selection the process of deliberately breeding certain specimens of plants or animals to encourage desired traits . binomial nomenclature the naming system developed by Carolus that represents two parts of a taxonomic name . The name is , the genus is always capitalized , and the species is always . For example Homo sapiens . the study of bones and other biological materials found in archaeological remains . biological species a of species as members that actually or potentially interbreed in nature . a subcategory of the primate that includes any primate considered an Old World monkey , an ape , or in the lineage of humans . This features nostrils and a dental formula . catastrophism the theory that changes in Earth fauna and were caused by supernatural catastrophic forces rather than evolution . a superfamily of the primate , subcategory , that consists of Old World monkeys . the of organisms based on of descendent lineages from a common ancestor derived characteristics physical traits that are present in related organisms but absent from their last common ancestor . They are often associated with a speciation event . diastema a space or gap between the canines and the other teeth that allows for the upper and lower teeth to bite together . ecological species a of species that explains differences in form and behavior as the result of adaptations to the environment and natural selection . the study of organism and developed and used largely by Indigenous peoples and other cultural groups . evolution changes that appear in a species over time . Evolution is dependent on genetic variation and natural selection to pass on traits that will increase survival of the species . foramen magnum the opening at the base of the skull where the spinal column and nerves enter to reach the brain . The position of the foramen magnum can be used to determine if a species was bipedal . forensic anthropology a branch of biological anthropology in which techniques are used to determine the sex , age , genetic population , or other relevant characteristics of skeletal or biological materials related to matters of civil or criminal law . fossils any remains , impression , or traces of living things from a former geologic age . gene alteration of the frequencies of alleles in a population that results from interbreeding with organisms from another population . genetic anthropology a branch of biological anthropology that uses molecular science to explore questions concerning human origins , early human migrations , and the appearance of disease across time . genetic drift random changes in the frequencies of alleles in a gene pool . genotype a complete set of genetic material found in an organism . gradualism the idea that species evolve slowly and continuously over long periods of time . great chain of being a concept detailing a hierarchical structure of all matter and life . a suborder of primates that contains , New World monkeys , Old World monkeys , apes , and humans . hominid the group representing all modern and

extinct great apes , including humans , chimpanzees , gorillas , orangutans , and all their immediate ancestors . the group representing modern humans , extinct human species , and all of immediate ancestors , including the genera Homo , and . a superfamily of the primate , subcategory , that consists of gibbons , great apes , and humanlike primates , including Homo and related fossil forms . homologous structures similar anatomical structures that appear in different species and suggest a common ancestor . hybrid zones areas where two distinct species mate and produce offspring industrial melanism the prevalence of dark colored varieties of animals ( for example , peppered moths ) in industrial areas where they are better against predators than paler forms . inheritance of acquired characteristics the disproved idea that an organism can pass on to its offspring physical characteristics that it has acquired during its lifetime . variation the genetic variation seen between two species . variation the genetic variation seen within a species . law of independent assortment a law of inheritance stating that different genes and their alleles are inherited independently . law of segregation a law of inheritance stating that when two alleles for a trait separate during the formation of new , these alleles will combine at random with other alleles . morphology the physical shape and structural form of an organism or species . mutation a change in the structure of a gene that results in a variant form that may be transmitted to subsequent generations . natural selection the process by which a species that is able to adapt and to pass on traits to its offspring ensures survival of the species formally introduced by Charles Darwin . paleoanthropology the study of the origins and predecessors of the present human species based fossils and other remains . a superfamily of primates from the early that is believed to represent the earliest New World monkeys , though they evolved in Africa . phenotype the set of observable characteristics or traits of an organism , such as color and structural morphology . phylogenetic species a of species based on individuals all possessing derived traits . a subcategory of the primate that comprises New World monkeys polygenic traits traits that are controlled by multiple genes instead ofjust one . the branch of biological anthropology dealing with the primates . Proconsul a genus of ape from the early . prognathism projection of the face , as seen in many nonhuman primates and early . a superfamily of primates from the early that is related to Old World monkeys and is believed to represent the earliest catarrhine primate . punctuated equilibrium a hypothesis holding that the evolution of species proceeds in a characteristic pattern of relative stability for long periods of time interspersed with much shorter periods during which many species become extinct and new species emerge . genus of the earliest primate or primate . reproductive isolation conditions that prevent potentially interbreeding populations from breeding . system the interrelationship between the diversity of plants and animals , humans environments , and the diversity of human culture and language . species a class of individuals that have some common characteristics or qualities . stratigraphy a branch of geology dealing with the , nomenclature , correlation , and interpretation of stratified rocks . a suborder that includes lemurs , and ( bush babies ) survival of the the theory that the most members ofa species will pass on their traits to later generations . sympatric speciation speciation without a geographic barrier . the plural form of taxon , used to signify all taxonomic groups . taxon a group or subgroup of organisms . taxonomy the science or technique of naming and

classifying life . uniformitarianism the concept that Earth surface was shaped in the past by geological processes . Summary Biological anthropology strives to understand how humans interact and behave in the present , how humans evolved biologically , and how humanity ancient ancestors lived in diverse climates and environments . The anthropological approach to exploring these questions is grounded in evolutionary theory . Charles Darwin was one of the to propose a mechanism by which evolution occurred , which he called natural selection . Natural selection is based on the premise that those with more favorable characteristics survive and reproduce at greater rates than those without them . Natural selection depends on the evolutionary processes of mutation , speciation , gene , and genetic drift . Darwin theory did not address how these favorable characteristics could be inherited . Gregor experiments on peas addressed this very question . work resulted in two very important observations . He observed that the two alleles for each trait separate during the formation of the sex cells and that the probability of having one trait does Critical Thinking Questions . How do anthropologists being human ?

What are some of the key differences between and ?

In what ways does the virus exhibit natural selection ?

How do anthropologists a primate ?

What is the difference between absolute and relative dating methods ?

What methods are commonly used when working with Bibliography visual predation hypothesis a hypothesis that explains the origins of unique primate traits as adaptations for preying on insects and small animals . not affect the probability that an individual will have another trait . Carolus is best known for creating the system that use today , which is based on physical similarities and differences . is a hypothesis about how species are related to one another and to a common ancestor . Today , biological anthropologists apply and to the current nonhuman primate and fossil record . It is in the that the fossil apes , such as Proconsul , are seen . The evidence of like fossils appears by the end of the . A large number of morphological changes observed in early suggest considerable environmental and climatic change . During the epoch , extending from to , the evolution of that were clearly bipedal is evident in the fossil record , as is evidence of cultures that used stone tools . The path is now ready for the next group in humanity evolutionary history to enter the scene . fossils ?

What is the difference between a prosimian and an anthropoid ?

What are some of the main differences between Old World and New World monkeys ?

What are some of the key characteristics seen in early , and what environmental forces may have contributed to those changes ?

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