What Traits Characterize Humans? Bipedal Locomotion Involves modifications of pelvis, femur, and backbone Various hypotheses regarding benefits, including free hands (vs. knuckle- walking and brachiation of great apes) Large Brain Size Requires omega fatty acids – high levels in marine organisms, nuts, marrow The Making and Use of Complex Tools Earliest stone tools produced by chipping flakes from a rock; oldest dated at ~ 2.5 mya (Oldowan Stone Tools) Opposable thumbs allow fine control and tight grips; include thick meta- carpals with broad heads for muscle attachment; three muscles not found in chimpanzees Language and Cultural Evolution Capacity for language is innate in humans (ex., children born deaf create languages) Modifications of larynx allow more tongue movement and great diversity of vocalizations (trade-off is greater chance of choking); hyoid bone of Neanderthals virtually identical to that of present-day humans Memes: ideas that can be disseminated via oral or written means, subject to modifications and non-genetic descent (impart information, cultural analogue to genes)

Fig. 34-37 Lemurs, lorises, and pottos New World monkeys Anthropoids ANCESTRAL PRIMATE Tarsiers New World monkeys Anthropoids Old World monkeys Gibbons Orangutans Gorillas Chimpanzees and bonobos Humans 60 50 40 30 20 10 Time (millions of years ago)

What are Some Notable Fossil Hominids? Pre-australopithecine: ~ 7 - 5 million years ago (mya) Sahelanthropus tchadensis: 6-7 mya (Chad); found in lake deposits from ancient Lake Chad Orrorin tugenensis: ~ 6 mya (Kenya); recent evidence for bipedalism based on CT scan of femur neck (controversial) Australopithecines: projecting faces; braincases < 550 cm3 Australopithecus africanus: ~ 2.8 - 2.4 mya; first hominid fossil found in Africa (“Taung Child”); discovered in coastal South African cave by Raymond Dart in 1925; more specimens found nearby in 1930s - 1940s Australopithecus afarensis (incl. “Lucy”): ~ 3.9 - 3.0 mya (Tanzania and Kenya); footprints in volcanic ash dated at 3.6 mya Early Humans: apparently coexisted with robust australo- pithecines in Africa Homo erectus (= H. ergaster): ~ 1.8 - 0.4 mya; widespread through Africa and Asia (ex. “Java man”); large braincase (> 850 cm3); most likely ancestor of more modern humans Homo neanderthalensis: ~ 0.3 - 0.03 mya; found in Europe Early Homo sapiens (incl. Cro-Magnon): ~ 0.1 mya - present; present-day average braincase = 1200 cm3; Cro-Magnon Man (30,000 ya) buried with animal bones, jewelry, and tools

Fig. 34-40 Paranthropus robustus Homo neanderthalensis Homo sapiens Paranthropus boisei Homo ergaster ? 0.5 1.0 1.5 Australopithecus africanus 2.0 Kenyanthropus platyops 2.5 Australo- pithecus anamensis Australopithecus garhi Homo erectus 3.0 Millions of years ago 3.5 Homo habilis Homo rudolfensis 4.0 4.5 Ardipithecus ramidus Australopithecus afarensis 5.0 5.5 Orrorin tugenensis 6.0 6.5 Sahelanthropus tchadensis 7.0

Fig. 34-41 (a) Australopithecus (b) The Laetoli footprints afarensis skeleton (b) The Laetoli footprints (c) An artist’s reconstruction of what A. afarensis may have looked like