Sites: East Africa: Hadar (NE Ethiopia), Laetoli (N. Tanzania), Kenya
Age: 3.9 to 3.0 million years ago Type specimen: LH-4 Specimens: There are more than 300 known individuals from this species collected.
Cranial capacity: 325 - 438 cm3 This is the earlies species for which a reliable brain and body size are available. It was about a third the size of an average modern human's brain and roughly the same size as a modern ape. Cranial architecture: Small, robust cranium with distinct maxillary prognathism and a compound temporal nuchal crest. Large anterior teeth. Broad nuchal crest, narrow nuchal angle, sagittal crest, flattened cranial base, anteriorly placed foramen magnum. Also a very low forehead and prominent brow ridges. There are many similarities between A. afarensis and chimpanzee skulls, although the canines are much smaller than those seen in modern apes. Dentition: Thick dental enamel. Canine diastema. Semi-sectorial premolar. Parallel tooth rows converging in the back of the mouth. Canines and molars are reduced in comparison to modern and extinct great apes, but still relatively larger than humans. Postcranial: Obligate biped but adept at grasping and climbing. A pronounced heel strike, adducted big toe with toe-off. Long ape-like fingers, intermembral index = 84. The human-like knees and pelvic structures leaves no doubt that A. afarensis walked upright. Some ape-like features remain - for example the hands and feet are more similar to apes but the big toe seems to have lost the grasping ability seen in apes. Orientation of the pelvis allowed it to walk upright but the length and grasp of the arms still allowed easy movement in the trees. Environment: Woodland and semi-arid savannah. Length and weight: Lucy: 28 kg, 105 cm. Others: 30 - 45 kg, 110 - 150 cm tall. Ancestor: A. anamensis A. afarensis seems to be the first species that appears after the split between hominids and chimpanzees. Descendants: A. africanus General: Habitual bipedality preceding change in facial architecture and brain size. It is clear that A afarensis walked upright, but had a very small brain. Extreme sexual dimorphism is seen in this species. References:
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