2. Primitive Archaic Genus Homo

3.  Modern human characteristics › Appeared at different times › Evolved at different rates  Extinct hominids show a mosaic of derived and ancestral characteristics

4.  Locomotion › Shift from inefficient to more efficient bipedality ca. 2 mya  Dentition › Enamel thickening ca. 4 mya › Gradual reduction of anterior dentition 4.5 mya to present › Gradual reduction of posterior dentition ca. 2.5 mya to present  Encephalization › Limited encephalization from 4 mya to 2.5 mya › Marked encephalization from 2.5 mya to ca. 150 kya

8.  Pelvis  Distribution of body mass  Relative limb-length  Position of foramen magnum  Lumbar vertebrae  Foot

15.  Age – estimated to be between 6 and 7 mya  Fossil remains › Nearly complete cranium › Several fragmentary mandibles › Isolated teeth  Cranial capacity – 320-380 cc  Classification uncertain – several possibilities  Position of foramen magnum suggests non- bipedal

16.  Chimp-sized brain  Hominin-like brow ridges  Canine wear pattern not ape- like  Thick hominin-like mandible

18.  Age ca. 6mya  Fossils remains – mandibles, femur, humerus, large molars, small canines › Femur suggests bipedality › Humerus suggests tree-climbing skills (but not brachiation) › Long bones suggest chimpanzee size › Teeth resemble later hominids

24. 24 “Gracile” (afarensis) “Robust” (aethiopicus)

25.  STS 5

27.  Au. africanus  P. boisei

28.  Age ca. 2.5 mya › Later Australopithecine  Limbs suggest bipedality  Incipient megadontia  Found with stone tools and butchered animal remains