The History of Our Tribe Hominini Textbook Part III Pliocene Epoch Chapter 11 Australopithecus afarensis

11 . southern ape I Afar region of Ethiopia ) Figure Forensic facial of . by Cicero Memes is licensed under . SITES Ethiopia Afar Depression ( and ) Chad el PEOPLE Donald , Mary , 85 INTRODUCTION , or the southern ape from Afar , is a species due to the famous Lucy specimen . It has been extensively studied by numerous famous . As mentioned , it is categorized as a gracile form of . The species survived for over a million years in the ing East African landscape , covering a broad geographic range . The famous footprints are attributed to Au . see Figures and ) They provided support for the then controversial idea of habitual , as well as the species presence in a more open environment . PHYLOGENY The most logical ancestor for Au . is Au . The two species overlapped in time and graphic space . Some have always believed that genus Home is descended from Au . Over time , others have changed their taxonomic scenarios from Au . to Au . which would formerly have been a sister lineage to Au . as our ancestor , and made Au . a side branch of the robust forms . Part of the argument for classifying Au . outside of our lineage had to do with aspects of their anatomy being more derived than our own , eg . the lateral flare of their ilia ( the plural of ilium ) Since the discovery of Au . Chapter 21 ) some scholars are back to favoring Au . in our ancestry . Figure recreation . by is licensed under . DISCOVERY AND GEOGRAPHIC RANGE The geographic range of Au . extends over from the site of in the Afar Depression of Ethiopia to the site in ( see Figure ) The holotype comes from . There is as to whether the Ethiopian and Tanzanian material should be attributed to the same species , since the sites are distant from one another and separated in time by 800 kya . In addition , if Au . ali is included as a geographic variant of the species , their range expands westward into Chad ( 2015 ) Thus this species was very successful at exploiting a variety of environments . 86 The History of Our Tribe

Figure Map showing the major fossil sites where specimens of and have been found . From Clement and ( 2013 , licensed under BY . With the discovery of Lucy ( see Figure ) in 1974 by Donald crew at the site of in the Afar Depression of Ethiopia , paleoanthropology gained momentum and the rush was on in East Africa to find more evidence of human origins . Certainly Louis and Mary recognized the importance of the Great Rift Valley , but upped the ante with his find . In addition , since Lucy skeleton was almost 40 complete ( making it one of the six most complete fossilized skeletons older than 100 kya ) much could be said about her anatomy and locomotor capabilities . Site AL 333 at yielded remains of 13 individuals , referred to as the First Family . Some researchers speculated that they may have died together and thus possibly represent a social group . However , recent examination of the deposition pattern at the site suggests otherwise ( see 2008 ) The more recently discovered Baby ( 33 ) see Figure 114 ) also known as ( meaning peace in the Afar language ) has contributed greatly to our knowledge of development in early . meaning nipple in the Afar language , is the name of the hill at the site of her ery . Discovered by in 2000 , the female has also been dubbed Lucy Baby due to its proximity to where Lucy was discovered . is now the oldest , most complete fossil . It took five years to extract the fossils from the surrounding sandstone matrix in which they were embedded . Thus we can see that not only is there difficulty in locating fossils , along with their living conditions in the desert environments of East Africa , the fossils may take years to process before all of their secrets can be revealed . Even more recent material from the Mille site in the Afar region has some scientists questioning whether the the Au . all fossil material attributed to a particular species ) might sent at least two species . has been suggested for the newer material . 87

Figure Baby . by is licensed under . Figure footprint cast . by Tim is licensed under A . Mary discovered the first and oldest ( Au . material at , and the holotype ( type specimen ) comes from that site . Her team recovered fossil material from 23 individuals , as well as the famous footprints . The trail of footprints extends for almost 25 They were made by two individuals walking side by side , with a possible third , smaller individual hopping within tracks already 88 The History of Our Tribe

Figure Replica of footprints . footprints replica by is licensed under made by one of the adults . The prints were formed when the walked through wet ash that had erupted from a nearby volcano . PHYSICAL CHARACTERISTICS Note Distinguishing primitive versus derived characteristics is difficult because we do not have all body parts to compare from one species to the next . In order to determine what changed , I am considering those aspects that are more as derived characteristics , regardless of whether predecessors possessed them . In other words , it is not perfect science ! All body parts are represented in the , ie . all fossils assigned to a particular species . While some debate surrounds the gait and locomotor efficiency of the species , it is fairly well accepted that they were habitual bipeds that retained some arboreal characteristics in the form of shoulder joints , an scapula , a high intermembral index , and curved finger bones . Their and lower limbs were unquestionably those of a biped , and the big toe , while slightly divergent from the other four digits , was not nearly the grasping digit seen in apes . The of their ilium , in the form of the iliac pillar , shows that weight was being transferred through the bone in the same manner as our own . While there is evidence of the bicondylar or carrying angle of the femur , the femoral head was small and the neck ( ing below the head ) was longer in and ( robust Chapters ) relative to Home species . Lovejoy believes that the degree of lateral iliac flare and long femoral neck in were associated with increased leverage of the deep gluteal muscles so that they were more efficient than modern humans ( Lovejoy 1988 ) As we gave birth to infants , our pelvic aperture had to expand laterally so that the femoral neck became shorter and the deep gluteal muscles became less stable relative to . The bony elements of the Home pelvis and hip had to become more robust to handle the increased force that the gluteal muscles generated on the bones ( discussed in Lovejoy 1988 and and Smith 2009 ) Based upon the footprints , it appears that the feet of Au . were slightly inverted , which would have helped with climbing . Au . had a prognathic , face ( see Figure ) a primitive skull morphology , and a small brain averaging 420 . They exhibited a slight sagittal crest for attachment of the muscle and a more pronounced nuchal crest , where their nuchal ( posterior neck ) muscles inserted on the posterior skull . The two crests were compound that the sagittal crest converged at the center of the nuchal crest . Their teeth were large and their dental arcade was , and thus more . The lower first premolar suggests a transitional phase , termed , between the 89

' A Figure Lucy . Luc Mexico by . is in the public domain . honing , sectorial ( premolar of the apes and our more bicuspid . The canines were monomorphic . Like Au . their molars were expanded . While their hands were capable of a precision grip , they did not have the same degree of mobility in their thumbs as later species of and . The conical thorax is linked to climbing and a large gut , and possibly the degree of lateral flare of the iliac blades . The Baby ( see Figure ) revealed inner ear adaptations that allowed them to distinguish their head from their torso this is important for running . Her brain was of similar size to that of a chimp . This indicates that they had a more prolonged developmental period , since the adult brain was , for the most part , larger than those of chimps . While chimps brains are , Au . were on average 434 , and ranged from 342 to 540 . She had both deciduous and developing permanent teeth in her jaws . Finally , her ribs were in anatomical position , which confirmed the conical thorax . Au . exhibited pronounced sexual dimorphism , with males and females averaging and 35 tall , respectively . Weights ranged from 64 to 99 . While the differences in size and morphology between the sexes might suggest that they were promiscuous and that males competed for females , their canines were monomorphic , suggesting . This is also supported by the change in the first mandibular molar to being . 90 The History of Our Tribe

Figure reconstruction . by is licensed under Review of Primitive Characteristics High degree of sexual dimorphism . Low cranial capacity . Compound crests Slight sagittal crest . Pronounced nuchal crest . Flat cranial base . Prognathic jaws with dental arcade and large incisors . Arboreal characteristics shoulder joints . scapula . a Long arms relative to legs . a Curved finger bones . Conical thorax . divergence of hallux . 91

Review of Derived Characteristics Inner ear adaptations allowed for more efficient running . Low cusp relief and thick enamel on molars . Loss of honing complex . Monomorphic canines . Precision grip adaptation in hands . Bipedal hips and lower limbs . Prolonged juvenile dependency and brain growth . ENVIRONMENT AND WAY OF LIFE This species inhabited a mixed woodland environment that is thought to have been more open than habitats . They could thus have exploited arboreal resources and moved between trees and forested areas in a fairly efficient manner . They are considered to have been , collecting wild plant foods , opportunistically hunting animals , and scavenging large game from carnivore kills . There is evidence of stone tool use at the , Ethiopia , site . Since Au . are the only known from that time and location , the tool use has been attributed to them . Researchers found cut marks on bones of two large animals that were dated to . Even more exciting is the recent discovery of tools in association with fossil material at the West Lake , Kenya , site of . While it was commonly accepted that used tools , this is the first evidence that they made them . The tools have been designated as the industry and have displaced the as the earliest tool industry , preceding it by years ( et al . 2015 ) The tools consist of anvils , cores ( stones from which flakes for cutting are removed ) and flakes ( see Homo Environment and Way of Life for more information on stone tools and their production ) Like extant great apes , they also would almost certainly have used biodegradable materials for tools , such as wooden , ivory , or antler digging sticks . Au . exhibited premolar and thick molar enamel for a tougher , more adapted diet , such as tubers ( large edible roots , yams ) However , they were not yet able to grind their food as well as later whose jaws could move laterally due to the reduction in canine size . The brain of shows that the juvenile dependency period was prolonged relative to chimps and hence the ancestor . In addition , once infants could not hang on with their feet , mothers would have had to put their babies down periodically . Dean Falk has suggested that this pattern of care may have led to language , in the form of what she refers to as ( Falk 2009 ) It is interesting that female chimps use tools more often than do males . In addition , woman the gatherer should share the limelight with man the hunter , as women in most traditional societies collected a larger share of their family food . Is it possible that women invented tools ?

How about language ?

For how long have we heard about the male provisioning model for the evolution of , man the toolmaker , man the hunter , men romancing women with the first language ?

Let stir up that cooking pot ! As mentioned , we are unsure of their mating and thus grouping pattern . Regardless of whether the First Family died together and represented a social group , Au . likely lived in groups for protection and possibly cooperation . Males were much larger than females but had lost the large canines and honing 92 The History of Our Tribe

Figure reconstruction at the National Museum of , Ethiopia . by is licensed under . Figure Lucy by Taylor . plex of Au . Thus while the degree of sexual dimorphism was much greater than in our own species , their monomorphic teeth suggest that they were transitioning toward while ing polygynous tendencies . While females may have mated , like a fair proportion of females in our own species , it may have been in their best interest to stick with their mate for help in raising their offspring , and not jeopardizing their safety with . 11 . 93