Lecture 4 The Human Ancestry Tree 1

 Paleoanthropology: “The fossil trail”  Archeology: artifacts, fire, burial…  Genetics:  Mitochondria DNA  Y-chromozones  X-chromozones  Other genes: FOXP2…  Body-morphology  Parasites 2

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 “Among not a few paleoanthropologists, there is a regrettable tendency to coin a new species name for every new fossil that differs the slightest from previous finds, leading to a proliferation of names of dubious value” (p. 63) 4

 Break up the evolutionary sequence to our “end of the bush” (not “ladder to the top”) into smaller steps  When did the change occur?  “Who” – what species are involved?  What major changes did it bring about?  Why (as a first approximation) did it occur? 5

 When: 200 MYA, “a smooth sequence”  What: Three bones instead of one in the middle year, “improving the frequency range and sensitivity of their years” (p.43) The ability to maintain a constant body temperature.  Why: Adaptive advantage in the face of climate change and nocturnal life 6

 When: around 65 MYA, “the Cretaceous- Tertiary (K/T) boundary”; Split between Strepsirhini (lemurs…) and Anthropoidea (monkeys, apes, humans), 50 MYA  What: “larger brains than most other mammals of similar size” (p.45, p.90), binocular color vision, grasping feet  Why: a diurnal, arboreal, (possibly also more social) life style: “social climbers” 7

 When: around MYA  What: As yet no “qualitative differences”  Why: Major geological changes, making the “old” and “new” worlds separate by large bodies of water 8

 When: around 20 MYA, over 30 known species  Gibbons, 20 MYA  Orangutans, 15 MYA  Oreopithecus (the “swamp ape”) – 10 MYA: bipedalism, precision grip (island life, no predators)  African apes (Gorilla, Pan, Homo), around 10 MYA  What: Greater dependence on terrestrial life  Why: The crucial dependence of the ecological niche 9

 Gorillas, around 10 MYA  Pan (Chimp and Bonobos), around 6 MYA  Hominids (or “Hominins”): our branch  What: see features on page 51, but most important initially: bipedalism  “Who” is the common ancestor?  Sahelanthropus tchadensis (7-6 MYA)  Orroin tugenssi (6 MYA)  Ardipethecus (6-4 MYA) 10

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 Why: not clear!  Drier climate with sparser resources (but 3.5 MYA is too late to explain the transition  Or wet, lake area as with Oreopithecus (the “swamp ape”): the “aquatic ape hypothesis” (Elaine Morgan)  Selection for hand use: carrying (babies?)  Change of social, and sexual lifestyle: decrease of size of (male) fangs occurred before bipedalism “… an environmental change providing similar incentives to our ancestors may have been enough to catalyze the change into habitual bipedalism” (p. 54) 12

13 “the most famous individual fossil of them all” (p. 57)

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 When: 4-2 MYA  Who:  Australopithecus anamesis  Australopithecus afarensis (“Lucy”)  Australopithecus africanus (in South Africa)?  Australopithecus robustus, Paranthropus (heavy chewing)?  Australopithecus garhi (first stone tools)? See figure on p

 “The australopithecienes demonstrate the opposite path, with their basically human like bodies and ape-sized brains” (p. 58)  “We have little indication of their having any culture beyond that of chimpanzees, and no reason to believe that they possessed language” (p. 60) 16

 When: 2.5 MYA  Who:  Homo habilis (sensu strictu)  Homo rudolfensis “habilines”  What:  Somewhat larger brains  More humanlike teeth  Stone tools (for the first time?)  “The differences between habilines and australopithecines are slight…” (: 61-63) 17

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 When: MYA “After the habilines, evolution towards a more human form is rapid”. (p. 64)  Who:  Homo ergaster (in Africa)  Homo erectus (in Asia)  Homo floresiensis (on Flores, Indonesia: by 18,000 YA)  What:  Considerably larger brains (by body size)  More sophisticated tools, fire, dispersal, boats…  Why: drier climate, life in the savannas: collaboration, and sign-based (gestural?) communication? 20

 When: MYA  Who:  Homo heidelbergensis (erectus-sapiens intermediate, 0.8 MYA)  Homo neanderthalensis (0.8 – 0.03 MYA, in Europe)  Homo sapiens ( MYA, in Africa)  No evidence for origin of Homo sapiens from Homo neanderthalensis, but recent evidence for some hybridization  Both species had large (but different) brains, and quite possibly language, though to different extent  They co-existed in Europe for 2,000-10,000 years 21

22 Same: Homo sapiens neanderthalensis and Homo sapiens sapiens Different: Homo neanderthalensis Homo sapiens

23 The Neanderthal Romeo and Human Juliet hypothesis Paul Mason Scientists have had trouble reconciling data from analyses of human mitochondrial DNA and the male Y chromosome. Analyses of human mitochondrial DNA indicate that we all share a common female ancestor 170,000 years ago. Analyses of the Y chromosome indicate that we share a common male ancestor 59,000 years ago (Thomson et al. 2000).Thomson et al Neuroanthropology, Oct 26, 2010

 Out of Africa: H. sapiens evolved from a small subpopulation of H. erectus in Africa, and spread out, replacing existing H. erectus and H. neanderthalensis  Multiregional evolution: The different “races” of H. sapiens evolved from the different local populations in Africa, Europe and Asia - Nearly all modern evidence supports “Out of Africa” 24

 Same species: All present H. sapiens can obviously interbreed  Fossils: The oldest H. sapiens fossils are in Africa  Archeology: Complex tools and ornaments appear first in Africa, about 150,000 years ago  Genes: Non-Africans share an even more recent common ancestor, as early as 60,000 year ago (a population “bottleneck”)  Body-morphology: Modern Africans resemble H. erectus in some details (teeth)  Parasites: DNA similarity of lice parallels human evolution and migration 25

 “The uniform language capacities of all human populations today prove that all adaptations for language, biological or otherwise (?), must have been in place in the last human ancestor of all living people, who most likely lived more than 100,000 years ago…” (p. 74)  However, percursors to language, cognitive as well as communicative, should have a much older date… 26