ANG 6930
Proseminar in
Anthropology IIA:
Bioanthropology
Day 6
ANG 6930
Prof. Connie J. Mulligan
Department of Anthropology
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New research in last week’s Science
• Out of Africa
– Did Modern Humans Travel Out of Africa Via Arabia?
A German-led team argues on page 453 of this week's issue of Science that
tools found under a rock overhang in Jebel Faya, United Arab Emirates, were
made by modern humans who may have crossed directly from Africa as part
of a migration spreading across Europe, Asia, and Australia.
http://www.sciencemag.org/cgi/content/summary/331/6016/387
– The Southern Route "Out of Africa": Evidence for an Early Expansion of
Modern Humans into Arabia
S. J. Armitage et al.
Artifacts in eastern Arabia dating to 100,000 years ago imply that modern
humans left Africa early, as climate fluctuated.
http://www.sciencemag.org/cgi/content/abstract/331/6016/453
– Stone tools found in UAE date to ~125kya and are similar to E African tools
• Pushes back exit of AMHS from Africa by tens of thousands of years
• Weak link – are tools truly E African, or could they be Neanderthal and not
evidence of an earlier exit by AMHS?
– What do the molecular data say?
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This week
•
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Origin of modern humans/Human biodiversity and race
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Homo floresiensis
Anatomically modern Homo sapiens
African replacement or multiregional evolution?
Global patterns of human genetic variation
Anthropological critique of race
Reading
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The Human Species, Chpts 13 (Origins of modern humans), 14 (Human
variation)
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Course packet
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Tattersall I. 2009. Human origins: Out of Africa. Proceedings of the National
Academy of Sciences 106:16018-16021.
Powledge TM. 2006. What is the Hobbit? PLoS Biology. 4:2186-2189.
Scheinfeldt L et al. 2010. Working toward a synthesis of archaeological,
linguistic, and genetic data for inferring African population history.
Proceedings of the National Academy of Sciences 107:8931-8938.
Serre D and Pääbo S. 2004. Evidence for gradients of human genetic diversity
within and among continents. Genome Research 14:1679-1685.
Haak W. 2008. Ancient DNA, strontium isotopes, and osteological analyses
shed light on social and kinship organization of the Later Stone Age. PNAS.
105:18226-18231.
“On the origin of art and symbolism” Science 2009, 323:709-711. Mulligan, Copyright 2011
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Next week (last week!)
•
Evolution of human life history and intelligence
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Population history, Natural selection and adaptation, Agriculture and civilization
Coursepack
Reproduction and fertility, Human growth and development, Aging and senescence,
Primate intelligence, Social behavior, Evolution of language
Reading
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Textbooks
The Human Species, Chpts 15 (Recent microevolution in human populations),
16 (Human adaptation), 17 (Biological impact of agriculture and civilization)
Course packet
“Are humans still evolving?” Science 2005, 309:234-237.
Gravlee CC et al. 2009. Genetic ancestry, social classification, and racial inequalities in
blood pressure in southeastern Puerto Rico, Public Library of Science ONE 4:e6821.
“Dental evidence suggests Neanderthals matured faster than we do” Science 2007.
Hawkes K. 2004. Human longevity: The grandmother effect. Nature 428:128-129.
Lähderpera M, Lummaa V, Helle S, Tremblay M, Russell AF. 2004. Fitness benefits of
prolonged post-reproductive lifespan in women. Nature 428:178-181.
Finch CE. 2010. Evolution of the human lifespan and diseases of aging: Roles of
infection, inflammation, and nutrition. Proceedings of the National Academy of Sciences.
“Civilization’s cost: The decline and fall of human health” Science 2009. 324:588.
Herrman E et al. 2007. Humans have evolved specialized skills of social cognition: The
cultural intelligence hypothesis. Science 317:1360-1366.
“Nonhuman primates demonstrate humanlike reasoning” Science 2007, 317:1308.
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Journal analysis due, take-home exam handed out and due next week
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Origin of Modern Humans
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Overview
• Morphology and fossil record of anatomically
modern humans
• Evolution of human behavior
– Upper Paleolithic technology and culture
– Revolution or evolution?
• Modern human origins debate
– Genetic data
– Fossil record
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The big picture
Evidence of modern human
behavior in Europe and
Australia
Archaic populations
evolving to anatomically
modern H. sapiens
Only modern H.
sapiens in fossil
record
Likely migrations from Africa
Years BP
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Evolutionary trends from
hominid to human
• What are some of the characteristics that
evolved to make us uniquely human?
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Evolutionary trends from
hominid to human
• What are some of the characteristics that evolved to
make us uniquely human?
– Bipedalism - ~4 mill yrs ago
• Ardipithecus ramidus (oldest hominid) and Australopithecus anamensis
– Smaller teeth (change in diet) - ~3 mill yrs ago
• Australopithecus afarensis (Lucy)
– Reduction in robustness - ~2.5 – 3 mill yrs ago
• Australopithecus africanus or A. garhi
– in brain size - ~2 – 2.5 mill yrs ago
• H. erectus
– Art (symbolic expression) – 40,000 yrs ago
• H. sapiens
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Morphology of modern H. sapiens
• Small face with protruding chin
• Rounded skull
– High vaulted cranium
– Vertical forehead, no supraorbital
torus
– No occipital bun or torus
• Less robust postcranial
skeleton
– Longer limbs with thinner-walled
bones
– More lightly built hands
– More narrow pelvis, shoulders
Cro-Magnon 1
~30 ka
Discovered 1868
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• Archaic humans on left
– Low cranial vault, large brow ridge, robust (large) face
• Modern humans on right
– High cranial vault, vertical forehead, prominent chin, less robust (smaller) face
• But, right (a) has a robust face and large brow ridges and right
(c) has a sloping forehead, a larger face and large brow ridges.
• much morphological variation b/t archaic and modern
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Fossil record of modern H. sapiens
Jurmain et al.
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Early modern Homo sapiens in
Africa and Near East
Site
Dates
Dating Method
Human Remains
Qafzeh
(Israel)
90 ka
Electron spin
resonance
20 individuals
Skhūl
(Israel)
90 ka
Electron spin
resonance
10 individuals
Klasies River 134-74 ka
Mouth
(S. Africa)
Electron spin
resonance
Several individuals;
highly fragmentary
Herto
(Ethiopia)
40Ar-39Ar
3 adults, one child
160-154 ka
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Modern H. Sapiens in Europe, Asia,
and Australia
Site
Dates
Human Remains
Abrigo do Lagar Velho
(Portugal)
24.5 ka
Four-year-old child
Cro-Magnon
(France)
30 ka
8 individuals
Ordos
(Mongolia)
50 ka (?)
1 individual
Kow Swamp
(Australia)
14-9 ka
40 individuals, including
adults, juveniles, and
infants
Lake Mungo
(Australia)
?60-30 ka
3 individuals, including one
cremation
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Evolution of modern human behavior
• Early modern humans able to create and
transmit complex symbolic behavior
• Moderns in W. Eurasia created tool industries
collectively known as Upper Paleolithic
– ~45-10 ka
– Upper Paleolithic peoples
• Technology of first moderns in Australia similar
to European Upper Paleolithic
• Sparse record in Asia, controversy in Africa
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Complex behavior in Upper Paleolithic
• Ecological range
– Early moderns extended range farther east and
north than previous hominids
– Inhabited difficult, cold, dry environments
• Technology
– Assembled more sophisticated and standardized
tools from wider variety of materials
– Constructed elaborate shelters
– Seafaring – 100 km of open ocean to Sahul (New
Guinea, Australia, Tasmania)
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Complex behavior in Upper Paleolithic
• Social organization
– Used raw materials from hundreds of kilometers away
– Long-distance trade networks, migrations
– Flint quarried in Poland identified in sites 400 km
away
• Symbolic expression
– Created art, ornamentation
– Performed ritual burials, practiced other symbolic
behavior
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Upper Paleolithic technology
• Shift from round flakes to
blade tools – Mode 4
– More time-intensive
– More efficient use of raw
materials
• Greater variety
– More specialized tools
– Distinctive designs for tool
types
• Increased variation in time
and space
1,3,4,5, 7,8,9 – points; 2 – borer; 6 – scraper
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Upper Paleolithic technology
• UP spanned depths of last
ice age
– Cold, dry grasslands, with
temperatures to -50F
– Required improved shelter
– Evidence of multifamily huts
• Clothing
– Bone awls and needles
common
– Russian burial site includes
caps, shirts, pants, shoes
– Fox, wolf remains without feet
Mezherich, Ukraine (15 ka)
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Upper Paleolithic peoples in Europe
better adapted to environment
• Higher population densities than
Neandertals
• Increased lifespan
– UP men sometimes reached 60, women rarely
reached 40
– Neandertals rarely reached 40
• Decreased injury and disease
– Relatively scare evidence of traumatic injury
– Slightly more evidence of disease, but less
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than among Neandertals
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Upper Paleolithic symbol and ritual
Hohle Fels (30 ka)
Le Chauvet (30 ka)
Lascaux (17 ka)
Venus of Willendorf
(25 ka)
Ivory horse from
Vogelherd, Germany
(30 ka)
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Human revolution or evolution?
• “Human revolution”
– Sudden appearance of complex adaptive and symbolic
behavior in Europe ~40 ka
– Klein argues that African archaeological record parallels
Europe
– Brooks and Yellon argue African record predates Europe
and shows more gradual change
• A revolution is interpreted as evidence of sudden
emergence of cognitively modern people
– How plausible is this scenario? How well supported is it
by the archaeological record?
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Potential objections to revolution
• Natural selection posits complex adaptations
by accumulation of small changes
– Fossil record and comparative primatology
suggest continuity in evolution of intelligence
– Punctuated event unlikely
• Archaeological record fundamentally biased
in favor of Europe
– 10 times as many sites in France alone as in
entire African continent
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Origins of modern behavior in Africa
• Sally McBrearty and Alison Brooks argue that
MSA is not equivalent to Middle Paleolithic
• Signatures of modern human behavior
gradually appear in Africa between 250-50 kya
• Transition from Middle (~200kya) to Upper
(~40kya) Paleolithic in Europe should not be
confused with origins of modern humans
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Origins of modern behavior in Africa
•
•
•
•
Blades appear early in MSA (240-280 ka)
There is regional variation in MSA industries
Refined bone tools at MSA sites (72 ka)
MSA peoples transported raw materials over
hundreds of kilometers
• MSA peoples built stone shelters and hearths
• There is evidence of decorative carving (77 ka),
beads (50 ka), pigment use (240-280 ka)
– New evidence of engraved ochre pieces 100 ka in S
Africa (Science, 2009, 323:569)
• Appear to be engraving, not just grinding off ochre, but who
knows if it’s ‘symbolic’
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What is ‘symbolic’?
The ability to construct symbols that convey meaning
Symbols must have a commonly understood meaning
• “If it’s a one-off, I don’t think it counts. It’s not
sending a message to anyone”
– Thomas Wynn, Science, 2009, 323:709-711
Cave art, Le Chauvet (30 ka)
Engraved ochre,
S Africa (77 ka)
A woman?
Berekhat Ram,
Israel (250 ka)
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X
Source: McBrearty and Brooks (2000) Journal of Human Evolution 39:453-563
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Theories on the origin of
modern humans
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Multiregionalism vs replacement
theories of human evolution
• What is multiregionalism?
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Multiregionalism vs replacement
theories of human evolution
• What is multiregionalism (also called regional coalescence)?
– Evolution w/i a single lineage spread throughout the world/Multiple
evolutions of anatomically modern humans throughout the world
• Species changed as a whole while retaining regional characteristics
– e.g. in brain size seen ~700,000 years ago, worldwide
– Based on continuity of million-year-old fossils and younger fossils in
multiple regions outside of Africa
• e.g. shovel-shaped incisors are more frequent in E Asia throughout many periods
• Besides temporal continuity, what could account for the supposed similarity
through time of certain morphological characteristics in the same geographic
region?
– Dependent on high levels of gene flow to keep us all the same species
so we can interbreed
– Postulates a global evolution of humans as opposed to a
geographically restricted one in Africa
– All humans over past 2 million yrs are part of the same evolutionary
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lineage
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Multiregionalism vs replacement
theories of human evolution
• What is the replacement theory?
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Multiregionalism vs replacement
theories of human evolution
• What is the replacement theory?
– Homo erectus spread throughout world, 1-2 million
years ago
– Anatomically modern humans left Africa ~150,000200,000 years ago and replaced all other hominid
populations throughout the world
• Depends on archaics and moderns being separate species
– Little or no interbreeding b/t modern humans and older
hominid populations
• What kind of scenarios might explain a lack of interbreeding?
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– All of our ancestors lived in Africa 200,000 YBP
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Assimilation Model
• Relethford’s proposed model
– Also called “weak” out-of Africa, primary African origin model
– Out-of-Africa w/ admixture b/t archaic, indigenous pop’s and
modern, invading pop’s
– Basically an intermediate theory b/t out-of-Africa (OOA) and
multiregionalism
• Despite what Relethford says, I don’t consider his theory multiregional
evolution b/c it’s simply interbreeding b/t 2 species (or subspecies) and
not independent evolution of modern traits as multiregionalism was
originally proposed
– An intermediate model is supported by recent molecular
genetic data indicating some interbreeding of AMHS with
Neanderthal (possibly) and Denisova
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Continuity with
no gene flow
Strict Out of Africa
(complete replacement)
Debate centers on
this range of admixture
100%
0%
25%
Percentage of local, archaic admixture in first modern humans in Eurasia
Adapted from Pearson, O.M. (2004) Evolutionary Anthropology 13:145-159
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Gene trees
• Compare DNA from pairs of living people,
build tree to track history of particular gene
• Many studies focus on mtDNA
– Maternal inheritance – no recombination
– High mutation rate – more accurate dating
– High copy rate – easier to recover in fossils
• Generally find two clusters – African and
non-African
• Does not falsify multiregional hypothesis
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Genetic diversity
• Greater heterogeneity in African populations taken as
evidence of antiquity – more time to accumulate
mutations
• Pattern could also be shaped by population size
• Relethford and Jorde: 50-70% of ancestors in Africa
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Genetic diversity analysis
• First split between African and
non-African populations
• Indicates African origin
• Same pattern could be
produced by slightly more
gene flow out of African than
into Africa
• However, genetic data all
show coalescence ~100200kya – not consistent with
multiregionalism
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Population size and modern human origins
• Genetic variation in living humans contains
signature of past population size
• Comparison of contemporary variation with
simulated populations suggests rapid growth of
population ~50 kya
• Possibly no more than 10,000 adults ~200 kya
• Assumptions uncertain: actual number may be
lower if there was a lot of population structure
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Bottom line - Mostly Out of Africa w/
possibility of non-African admixture
Europe
Africa
Asia
Present
“Modern
humans”
Time
“Archaic
humans”
Past
Europe
Africa
Asia
Adapted from Relethford (2003)
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Study of human variation
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Anthropology and Race
• History of anthropology tied to history of
race concept
• Early anthropologists played central role in
creating racial worldview
• Later, anthropologists played major role in
dismantling American racial worldview
• Today, anthropologists engage in public
education about race and human diversity
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Race in early Anthropology
• Racial typology was guiding aim of 19th and
early 20th century anthropology
• Unilinear evolution
– Rank human groups along single evolutionary
path from “savagery” to “civilization”
– Cultural and biological anthropologists
• Biological determinism
– Basic assumption that biology → culture
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Boasian critique of race
• Statistical averages do not reflect ideal types
– No discrete boundaries
– Significant within-group variation
• Racial types are not fixed
– Heredity and environment
– Plasticity
• Race language culture
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Boas’s immigrant study
• Commissioned by U.S.
Immigration Commission
• Boas and team of 13
assistants collected data on
nearly 18,000 people
• Largest data set of family
measurements
• Best remembered for
critique of cephalic index
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Cephalic Index
• Anders Retzius devised
cephalic index and built a
theory of history on it
• Ratio of head breadth to
head length
• Treated as fixed marker of
racial phylogeny
• Boas’s demonstration of
change in generation
undermined typology
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Gravlee, Bernard, Leonard
(2003)
• Reanalyzed data Boas
published in 1928
• Address three key
findings
– Differences between
foreign- and U.S.-born
– Increasing influence of
environment over time
– Differences between
U.S.-born children and
foreign-born parents
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Rise of No-Race Anthropology
• Cultural and biological
anthropologists played a
key role in challenging race
• Livingstone: “There are no
races, there are only clines”
• After WWII, no-race position
came to mean no
discussion of race in
anthropology
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Race returns to Anthropology
• AAPA (1996) and AAA (1998) released statements
on race
• Anthropologists advised Census on race
• AAA launched $4 million public education project
• Anthropologists engaged in interdisciplinary
debate on human variation
• Growing focus on social reality of race and racism
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Health, race, and anthropology
• Persistence of racialgenetic determinism in
biomedicine
White female
80
75
Black female
White male
70
65
Black male
60
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
• Opportunity to advance
anthropological critique
of race
Life Expectancy at Birth (Years)
• Substantial disparities in
life and death
85
Source: National Center for Health Statistics
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Race in medicine today
• Race is ubiquitous in contemporary medical
research and clinical practice
• Medical education
– Medical students instructed about genetic basis
of racial disparities in health
– Clinical case presentations cite patient’s race
• Race is used routinely and uncritically in
clinical and epidemiologic research
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Racial-genetic determinism
• Williams’ review of medical dictionaries reveals
assumption that race is biology
• But explicit definitions of race in medical
research are rare
– Not one of 121 studies in AJE, 1960-1990, defined
race
• Race often used as proxy for unspecified
combination of behavioral, environmental, and
genetic factors
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Is breast cancer in young
Latinas a different disease?
• Biffl et al. aim to “clarify the relationship between
race/ethnicity and disease severity”
• They conclude that “young Latinas might have more
aggressive disease compared with other young women”
• They do not propose why this difference might exist,
nor do they define “race/ethnicity”
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Published commentaries note
ambiguity of “race/ethnicity”
“[Note] how primitive we are in identifying what patient sample we’re
talking about.…How we racially profile our patients in these studies is
important.…I think in the future, we’re going to have to get more
sophisticated with identifying gene pools and not use the color of the
patient’s skin”
Dr. Victor J. Zannis
“I think it’s really important that you define what you mean by Latina
because this could mean Mexican, it could mean Central American, it
could mean Puerto Rican, and I don’t think that you’re dealing with a
genetically identical gene pool in the best of circumstances.”
Dr. Maria D. Allo
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BiDil – the first “ethnic drug”
http://www.nitromed.com/BiDil.shtml
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Critique of race as biology
• Persistence of racial-genetic determinism requires
clarity in critique of race
• Two fallacies in racial-genetic explanations of
health
– Population differences in health are genetic in origin
– Race is a reliable marker of genetic differences
between populations
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Fallacy 1 – Population differences
are genetic in origin
• Assumption often justified by reference to classic “racial”
diseases
– Sickle cell in African Americans
– Tay-Sachs in Ashkenazi Jews
– Cystic fibrosis in Northern Europeans
• But, these disease aren’t limited to these populations, just
present at higher frequencies
• These diseases expose weakness of racial model
– Not distributed along racial lines
– Single-gene disorders, not complex phenotypes like ‘race’
– Complex phenotypes – multiple genetic and environmental
factors
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Fallacy 2 – Race is valid marker
of genetic differences
• Most genetic variation among humans occurs
within populations, not between them
• Variation in gene frequency is distributed
continuously, or clinally, in response to selection
or genetic drift
• Human biological variation is discordant – traits
vary independently of one another in response to
selection or genetic drift
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Why racial classification doesn’t work
• Most genetic variation among humans
occurs within populations, not between them
• Variation in gene frequency is distributed
continuously, or clinally, in response to
selection or genetic drift
• Human biological variation is discordant –
traits vary independently of one another in
response to selection or genetic drift
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Human genetic diversity in
comparative perspective
• Most genetic variation among humans occurs
within populations, not between them
– Not true in other species
• Two humans taken at random are more genetically
similar than are two chimpanzees taken at random
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Apportionment of human genetic diversity
Total Species
(100%)
Between Regional
Populations
(10%)
Within Regional
Populations
(90%)
Between Local
Populations Within
Regional Populations
(5%)
Between Individuals
Within Local Populations
(85%)
• Confirmed recently with 377 microsatellite loci in 1,056
individuals from 52 worldwide populations (Rosenberg et al. 2002)
– Within population variation – 93-95%
– Between regional groups – 3-5%
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Why racial classification doesn’t work
• Most genetic variation among humans
occurs within populations, not between them
• Variation in gene frequency is distributed
continuously, or clinally, in response to
selection or genetic drift
• Human biological variation is discordant –
traits vary independently of one another in
response to selection or genetic drift
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• Sampling strategy may create an artifact of
geographic clusters
Serre, D., and S. Paabo. 2004. Genome Research 14:1679-1685.
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Variation in skin color in 22 populations
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Clinal distribution of skin color
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Skin color and settlement of U.S.
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Why racial classification doesn’t work
• Most genetic variation among humans
occurs within populations, not between them
• Variation in gene frequency is distributed
continuously, or clinally, in response to
selection or genetic drift
• Human biological variation is discordant –
traits vary independently of one another in
response to selection or genetic drift
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Discordant nature of “racial” traits
• Race concept assumes
that traits are bundled
together
• Individual traits respond to
different forces, such as
selection or genetic drift
• Unless linked on same
chromosome, traits are
inherited independently
Layers represent 4 traits that vary
continuously, but independently. Each
core represents a single individual and
their ‘sampling’ of each trait
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Global distribution of skin color
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Distribution of blood type A
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Distribution of blood type B
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Overall genetic similarity
Contour map based on sample of 120 genes from 42 populations
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Using current
analytic methods and
huge DNA datasets,
we can distinguish
between populations
in astonishing detail,
far beyond ‘races’
Nothing ‘magical’
about racial
boundaries, just
need enough
markers
A statistical summary of > ½ million genetic variants from 1,387 Europeans based on principal component
axis one (PC1) and axis two (PC2). Small colored labels represent individuals and large colored points
represent median PC1 and PC2 values for each country. PC axes are rotated to emphasize similarity to the
geographic map of Europe. AL, Albania; AT, Austria; BA, Bosnia-Herzegovina; BE, Belgium; BG, Bulgaria; CH, Switzerland; CY,
Cyprus; CZ, Czech Republic; DE, Germany; DK, Denmark; ES, Spain; FI, Finland; FR, France; GB, United Kingdom; GR, Greece; HR,
Croatia; HU, Hungary; IE, Ireland; IT, Italy; KS, Kosovo; LV, Latvia; MK, Macedonia; NO, Norway; NL, Netherlands; PL, Poland; PT,
Portugal; RO, Romania; RS, Serbia and Montenegro; RU, Russia, Sct, Scotland; SE, Sweden; SI, Slovenia; SK, Slovakia;
TR, Turkey;
UA,
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So what do we do with race?
• Biological evidence suggests that race is not
a useful way to describe biological variation
• Some propose that we should jettison race
• Others note that race is a pervasive social
fact, even if it is a dubious biological one
• View race as a culture-bound emic construct
in cross-cultural perspective
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Discussion
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