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Earliest Hominins

Earliest Hominins. Hominin Phylogeny. Genus Homo. Archaic. Primitive. Mosaic Evolution. Modern human characteristics Appeared at different times Evolved at different rates Extinct hominids show a mosaic of derived and ancestral characteristics. Hominin Evolutionary Sequences.

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Earliest Hominins

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  1. Earliest Hominins

  2. Hominin Phylogeny Genus Homo Archaic Primitive

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

  4. Hominin Evolutionary Sequences • 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

  5. Bipedality

  6. Skeletal Indicators of Bipedality • Pelvis • Distribution of body mass • Relative limb-length • Position of foramen magnum • Lumbar vertebrae • Foot

  7. Primate Taxonomy (DNA-based)

  8. Dentition

  9. Dentition comparison

  10. Early Hominin Molar Size

  11. Primitive Hominins

  12. Sahelanthropustchadensis • 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

  13. Sahelanthropus tchadensis • Chimp-sized brain • Hominin-like brow ridges • Canine wear pattern not ape-like • Thick hominin-like mandible

  14. Orrorin tugenensis • 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

  15. Orrorin tugenensis Femur

  16. Ardipithecusramidus

  17. Archaic Hominins

  18. GRACILE & ROBUST AUSTRALOPITHECINES “Robust” (aethiopicus) “Gracile” (afarensis)

  19. Australopithecus africanus • STS 5

  20. Paranthropus boisei (OH 5)

  21. “gracile” vs “robust” archaic hominins • Au. africanus • P. boisei

  22. Australopithecus ghari • Age ca. 2.5 mya • Later Australopithecine • Limbs suggest bipedality • Incipient megadontia • Found with stone tools and butchered animal remains

  23. Australopithecus ghari

  24. The Genus Homo

  25. Homo [?] habilis

  26. Cranial Comparisons

  27. DmanisiHomo erectus

  28. Homo ergasterKNM-ER 3733

  29. Comparison of Later Forms of Homo

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