The History of Our Tribe Hominini Textbook Part III Pliocene Epoch Chapter 10 Australopithecus anamensis

10 . southern ape I from the lake in the language ) Figure Distal humerus of . bane ( University of Zurich by Nicolas is licensed under . SITES Bay and , Kenya PEOPLE and Alan Walker INTRODUCTION is the earliest known . We do not know nearly as much about the species as about other due to a paucity of fossil material .

PHYLOGENY Au . may be descended from the lineage or a heretofore undiscovered group . Lucy species , Au . may be descended from Au . DISCOVERY AND GEOGRAPHIC RANGE Multiple ( most notably and Alan Walker ) are credited with the discovery of Au . material . The species name refers to the Lake area of Kenya where the fossil sites of and Bay are located ( see Figure ) There are also newer fossils from the Middle Awash area of the Afar Depression of Ethiopia ( see Figure ) The Ethiopian material is close in time and graphic space to an site , lending some support to the possibility of their phylogenetic relatedness . There is some controversy over the lumping together of material from different levels and in Kenya that could have confounded the description of the species characteristics . Figure sites . by is licensed under . PHYSICAL CHARACTERISTICS The species is thought to have been highly sexually dimorphic in body and canine size . Much of the morphology is , and hence primitive . The jaws and teeth are the most primitive of any , which is not surprising since it is the oldest . Unlike the parabolic tooth arrangement in the jaws of later , Au . had an apelike , dental arcade wherein the cheek teeth are nearly parallel ( see Figure ) Their jaws were also prognathic and their canines were larger than dent species . However , the molars were expanded with thick enamel and low like later . In addition , aspects of the elbow , knee , and tibia were more derived , indicating its bipedal mode of tion . 82 The History of Our Tribe

Figure ) of extinct ape illustrating dental arcade . jaw by is licensed under Review of Primitive Characteristics High degree of sexual dimorphism . Prognathic jaws with parallel cheek teeth . Larger canines than subsequent species . Review of Derived Characteristics Expanded molars , low cusp relief , and thick enamel . Bipedal adaptations of elbow , knee , and tibia . ENVIRONMENT AND WAY OF LIFE Fossils have been found in a variety of settings , such as lakeside , woodland , and more open areas . The species likely slept in trees and foraged both in trees and on the ground , as they moved around their home range in search of resources and mates . The high degree of sexual dimorphism and the presence of the honing complex suggest a polygynous or mating system . The mer may have involved a social organization and the latter , a pattern . A system may have looked more like that of gorillas , where both males and females tend to leave their natal group . However , if we use chimps and bonobos as a model of our ancestral social 83

, it was more likely a social organization , with males staying in their natal group ( and females leaving at sexual maturity to join another . While it is easy to use our more closely related relatives to reconstruct our past behavior , we must remember that social organization is a function of both phylogeny and ecology . Taking both into consideration , in combination with their anatomy , it is more likely that Au . were more . Their teeth do not have the higher of the more gorilla , so their diet was likely more and hence a combination of fruit , tender greens , and opportunistic animal matter . As mentioned in Chapter , that type of diet is harder to come by and females may have needed males to defend a territory for their nutritional needs and those of their offspring . Interestingly , isotopic analyses of ( robust from South Africa ) fossil material show that while males were from the area where the fossils were found , females were not . Thus we now have a fourth line of evidence favoring male . 84 The History of Our Tribe