2. Human Evolution 12.6

3. Laetoli Footprints Laetoli footprints clearly show that the creatures who made them were fully bipedal Big toe hardly diverges from the rest of the foot, unlike in apes Gait = “heel-strike” followed by “toe-off” – the way modern humans walk

4. Orrorin: Earliest Evidence for Walking on Two Legs? How far back in time does the record of bipedalism extend? Fossils from Turgen Hills in Kenya have been dated to about 6 mya Include: upper portion of a femur, lower portion of the humerus, some lower jaw fragments, & teeth Arm bone = virtually identical to that of a chimpanzee Femur = more human-like,most important for showing adaptations for walking on 2 legs Was Orrorin a direct human ancestor, or close to the common ancestor of chimps and humans?

5. Ardipithecus: Earliest True Hominid? Between 4.5 and 5.5 mya from the Middle Awash valley site Remains very fragmentary: limb bones, toe bones, jaws & teeth Straight toe bones suggest it may have been bipedal Ardipithecus & Orrorin are candidates for last common ancestor of chimps & humans Each have mosaic of features seen in later hominids & modern chimpanzee IT MAY WELL BE THAT THE LAST COMMON ANCESTOR OF CHIMPS AND PEOPLE HAD A MIX OF FEATURES: SOME RETAINED IN HUMANS, OTHERS RETAINED IN CHIMPS!

6. Hominid Evolution

7. Australopithecus anamensis Turkana region of Kenya Dated to 4.2-3.9 MYA Probably walked upright Teeth covered with enamel much thicker than that of Ardipithecus, so diet may have had hard-to-chew foods

9. Hominid Evolution Hominids = “great apes” – Chimpanzees, gorillas, humans, and orangutans Numerous intermediary fossils have been found – But scientists disagree on which are human ancestors and which are evolutionary dead ends

10. “Lucy” Australopithecus afarensis 3 mya

11. Modern HumanChimp Lucy

12. Australopithecus afarensis Eastern Africa 3.9 – 3.0 MYA Pelvis and leg bones resemble modern humans in some ways Sexually dimorphic in body size May have been adept at tree climbing, based on curvature of finger and toe bones Ape-like features: – Small brain case – averaging 430 cc – Prognathic (jutting out) face – U-shaped palate vs. the parabolic shape of modern humans – Reduced canines

13. Australopithecus africanus Taung Child STS 71 – Most complete A. africanus skull Partial skeleton of A. africanus discovered in 1950s Ms. Ples – best known A. Africanus cranium – front view Ms. Ples – best known A. Africanus cranium – lateral view

14. Australopithecus africanus 3.3 – 2.5 MYA in Transvaal region of South Africa First australopithecine to be described (1924) More globular cranium & slightly higher ratio of brain to body size Teeth & face appear less ancestral (reduced in size relative to earlier forms, face less prognathic) May represent 2 species or one very sexually dimorphic species Proportions of arm to leg lengths may be more ape-like than in A. afarensis

15. “Homo habilis” (KNM-ER 1813)

16. Human Evolution Homo habilis – 2.4 to 1.4 million years ago – Fossils found in southern and eastern Africa – Used simple bone and stone tools – Nicknamed “handy man” Homo erectus – 1.8 million years ago to 70,000 years ago – First human ancestor to walk fully upright – Some made complex stone tools – Example – “Peking Man” – Descendants were humans and neanderthals

17. Neanderthals Homo sapiens neanderthalensis Circa 400,000 to 30,000 years ago Lived in Europe and Asia Archaeogenetics – analysis of ancient and modern DNA Comparison of human and Neanderthal DNA shows that humans are not descended from Neanderthals Genes reveal that Neanderthals had red hair and fair skin Fair skin developed to aid in the absorption of Vitamin D from the sun in areas far north of the equator Convergent evolution – different species (such as humans and Neanderthals) developing same characteristic(s)

18. Humans – Homo sapiens “Homo” (Latin) means “man” or “human” “Sapiens” (Latin) means “wise” or “intelligent” “Homo sapiens” = “wise man” or “wise human” Humans and Neanderthals both considered “sapiens” Anatomically modern humans in Africa by 200,000 years ago Middle Paleolithic period

19. Humans – Homo sapiens sapiens – “Us” Fully modern humans (like us) in Africa by around 60,000 years ago Descendants of Mitochondrial Eve and Y-chromosomal Adam Culture, language, music, etc. “Out of Africa” theory Archaeogenetics (analysis of ancient and modern DNA) shows that humans began spreading throughout, and out of, Africa beginning around 60,000 years ago Early human migrations Humans left southeastern Africa and spread throughout the continent Humans traveled along the Indian Ocean to reach Australia By 10,000 years ago, modern human beings had spread all over the globe