lecture 4 the human ancestry tree 1. paleoanthropology: “the fossil trail” archeology:...
TRANSCRIPT
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The Origins of LanguageJordan Zlatev
Lecture 4The Human Ancestry Tree
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How do we reconstruct it? Paleoanthropology: “The fossil trail” Archeology: artifacts, fire, burial… Genetics:
Mitochondria DNA Y-chromozones X-chromozones Other genes: FOXP2…
Body-morphology Parasites
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Our part of “the bush”
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The problem of “species”
“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)
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From reptiles to Homo sapiens
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?
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From reptiles to mammals
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
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From mammals to primates
When: around 65 MYA, “the Cretaceous-Tertiary (K/T) boundary”; Split betweenStrepsirhini (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”
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From Anthropoidea to Catarrhini (old world monkeys and apes)
When: around 40-30 MYA
What: As yet no “qualitative differences”
Why: Major geological changes, making the “old” and “new” worlds separate by large bodies of water
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From Catarrhini to Hominodea (Apes)
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
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From Apes to Hominids
Gorillas, around 10 MYA Pan (Chimp and Bonobos), around 6
MYA Hominids (or “Hominins”): our
branchWhat: 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)
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(Partial) bipedalism
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From Apes to Hominids
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)
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“Lucy” and Donald Johanson
“the most famous individual fossil of them all” (p. 57)
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Clear bipedalism, stone tools
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From australopithecines to Homo
When: 4-2 MYAWho:
Australopithecus anamesis Australopithecus afarensis (“Lucy”) Australopithecus africanus (in South
Africa)? Australopithecus robustus, Paranthropus
(heavy chewing)? Australopithecus garhi (first stone tools)?See figure on p. 56
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From australopithecines to Homo
“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)
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“Habilines”: a transitional species
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)
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But then comes a major step…
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Homo erectus: a clear ancestor
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From habilines to ergaster/erectus
When: 1.7-0.5 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?
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From H. erectus to H. sapiens When: 0.8-0.1 MYA Who:
Homo heidelbergensis (erectus-sapiens intermediate, 0.8 MYA)
Homo neanderthalensis (0.8 – 0.03 MYA, in Europe) Homo sapiens (0.2-0.1 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
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Same or different species?
Same: Homo sapiens neanderthalensisandHomo sapiens sapiens
Different: Homo neanderthalensis
Homo sapiens
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The Neanderthal Romeo and Human Juliet hypothesisPaul 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).
Neuroanthropology, Oct 26, 2010
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Two conflicting theories
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”
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Evidence
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
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Implications for the evolution of language
“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…