Genus Homo Archaic Primitive

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

 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

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

     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

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

  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

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

 STS 5



Au. africanus



P. boisei

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