The History of Our Tribe Hominini Textbook Part IV Pleistocene Epoch Chapter 18 Paranthropus boisei

18 . beside human I surname of one of the financiers ) Figure . side of Zurich by Nicolas is licensed under . SITES Ethiopia Deposits and Kenya , West Lake , and Fora and PEOPLE Mary and Richard INTRODUCTION In the first course that I took in physical anthropology , I was most fascinated by the face from Gorge ( see Figures 181 and ) and the mandible from the site near Lake Natron . I still remember the first time I saw them , and the species has always been for me one 124

of the more interesting discoveries in paleoanthropology . Their faces , jaws , and cheek teeth were massive and truly unforgettable . While the material is attributed to Mary , it was her husband Louis who announced to the world that he had his He had been finding tools of what are now termed the tradition and was hoping to discover who had made them when Mary discovered the first fossils . They were assigned to a new genus and species , or human from East Africa . is a derivation of the archaic term for an area of the East African coast , and was the name of one of the financial supporters ( Wikipedia contributors ) Louis claimed that they had their toolmaker , but many did not agree with his conclusion . They thought he had found a big , dumb , herbivorous , bipedal ape that would not have had the cognitive abilities to produce stone tools . Hand bones have been attributed to the species by some researchers . If they are correct in their assignment , the species may have been capable of tool manufacture and efficient use . However , while their brains were somewhat larger than earlier species , we still do not know if they had the cognitive abilities and thus whether tools from East African sites can be attributed to them . Figure Gorge , by David , Fossils from more than 100 individuals have been recovered in the last 55 years . Over time , the genus has changed from to to , but some researchers are still using genus . PHYLOGENY Support for being descended from Au . has steadily increased . However , some still group as a sister species of and believe that they descended from Au . The two more derived forms share a molar trait with Au . in that the second molar ( is larger than the third ( Members of the latter group , such as Henry , contend that the more primitive Au . is an example of homoplasy or convergent evolution , making the robust traits . have tended to be conservative in their acceptance of common ancestry is more parsimonious . 18 . 125

Except for the possible Au . a scenario , the robust were evolutionary as far as we know . Figure reconstruction of . by is licensed under . DISCOVERY AND GEOGRAPHIC RANGE Mary discovered the first material in 1959 at Gorge , see Figure ) Nicknamed Nutcracker Man , or Dear Boy , the skull and face were dated to . Fossils attributed to the species have since been found at other sites in ( Kenya ( West Lake , and Fora in the East Lake area ) and Ethiopia ( the Deposits and ) Richard discovered the Fora fossils . Thus , like Au . the species had a broad geographic range and survived for over a million years . 126 The History of Our Tribe

Figure by Taylor . PHYSICAL CHARACTERISTICS While the robust forms are somewhat larger than the gracile forms , they do not differ much . It is their skulls that set them apart had the most pronounced masticatory adaptations , so that relative to the other two species , they are termed . Along with the other robust forms , they shared a skull , face , and mandible large molars and a compound crest ( not compound in ) large muscles of mastication and nuchal muscles to support their heavy skulls large , zygomatic arches and a supraorbital torus to absorb the stress generated by chewing . According to some researchers , they shared the following with and Homo skull base more orthognathic face lower face tucked under the , thus increasing chewing force on the molars a 18 . 127

more parabolic dental arcade and a longer thumb with broad , flat , distal phalanges that gave them better opposition and gripping power . The sagittal crest in and was more anteriorly positioned relative to An . In combination with less prognathism and the fact that their face was tucked under the , the action and strength of the muscle was concentrated on the cheek teeth . The degree of robusticity and the size of characteristics were unique to . The were large , heavy , and widely , making their faces very broad and the temporal fossa ( the space between the zygomatic and the temporal bone ) very deep . Again , this facilitated the passage of the muscle to insert on the mandible and expanded the attachment and anchoring of the masseter muscle . The mandible was massive , with a very robust and deep body and tall rami ( vertical side portions ) and the temporomandibular ( jaw ) joint was exceptionally large . Their front teeth were so dwarfed by their enormous cheek teeth , they almost look juvenile . Their were , and some had a third root . The third molar exhibited a unique wrinkling pattern . Their quotient ( was , ing that their teeth were times larger than would be expected . had the largest supraorbital torus of the robust forms . They were somewhat more than past species , with a cranial capacity of 514 ( range ) Like all , the species was sexually dimorphic , with males at ' 137 ) tall and 108 ( 49 ) and with more pronounced crests and females at 41 ( 124 ) and 70 ( 34 ) Figure mandible . mandible . by Matt is licensed under Review of Derived Characteristics Same robust characteristics as seen in Au . with the following differences More robust characteristics . 128 The History of Our Tribe

Sagittal crest more anteriorly placed . Large supraorbital torus . Huge molars and . Large , heavier mandible . Flexed skull base . More orthognathic face . Lower face tucked under , maximizing chewing force on molars and . More parabolic dental arcade . Longer thumb with broad , flat distal phalanges . ENVIRONMENT AND WAY OF LIFE While they still had relatively long arms , one seldom hears anything about the arboreal habits of the robust forms . In East Africa , that is not too surprising since the forests had receded and the grasslands had expanded . By , deep sea cores reveal an increase in the type of environment , the area south of the Sahara that consists of dry grasslands and scrub forest . Based on evidence from their molars , all or most of which are ground flat , likely on open , plants . Silt on terrestrial foods would have contributed to the wear patterns . The availability of foods must have gotten even worse by the time of , because their chewing and capabilities were increased relative to Au . They ate a high proportion of plants , open and more adapted grasses and shrubs . It is thought that they likely survived on hard , tough , and brittle fallback foods during periods of preferred resource scarcity . This is another possible example of niche partitioning , in that sympatric Homo species may not have been able to utilize or digest either food category . Isotopic analyses to calculate the ratio in fossilized bones of Au . and have mined that they ate some animal matter . It is possible that did as well . While we do not know if they were scavenging or hunting animals , it is very possible that early ate insects and insect larvae . All extant great apes consume social insects ( ants and termites ) and they derive a surprising degree of value from them . In traditional human societies , larvae are a favored resource . It seems likely that lived in small groups or did they ?

Living in a more open environment in Africa , there would seemingly have been safety in numbers . Since they were adapted to savanna resources and could fall back on food items that were unavailable to other sympatric species , they may have avoided strong and feeding competition . We also know that may have been necessary , as females were not as as their quadrupedal ancestors . They had babies that could not hold on and were surrounded by males that could rape or commit infanticide . There is an argument that monogamy is a male adaptation that increases paternity assurance while reducing the risk of infanticide . We know that males compete for mates , and the high degree of sexual dimorphism in supports that fact . With all of the preceding arguments in mind , is it possible for apes with a tendency toward monogamy to live together without all of the rules and laws seen in modern humans to keep male competition and jealousy in check ?

While we could argue that they also could have lived in pairs with their dependent offspring and never ventured far from trees , how did females climb with their infants ?

We still have many unanswered questions about behavioral ecology ! 18 . 129 Figure 186 King of the termite mound by Taylor . 130 The History of Our Tribe