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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 mammalsWhen: 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 primatesWhen: 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…