Mulligan, Copyright 2011 All rights reserved ANG 6930 Proseminar in Anthropology IIA:...

Mulligan, Copyright 2011 All rights reserved

ANG 6930Proseminar in

Anthropology IIA: Bioanthropology

Day 6

ANG 6930

Prof. Connie J. Mulligan

Department of Anthropology

Mulligan, Copyright 2011

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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• Origin of modern humans/Human biodiversity and race

• Homo floresiensis• Anatomically modern Homo sapiens• African replacement or multiregional evolution?• Global patterns of human genetic variation• Anthropological critique of race

• Reading– The Human Species, Chpts 13 (Origins of modern humans), 14 (Human

variation)

– Course packet• 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.


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Next week (last week!)• Evolution of human life history and intelligence

– Textbooks• 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– 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.

• 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

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Evidence of modern human behavior in Europe and Australia

Archaic populations evolving to anatomically modern H. sapiens

Likely migrations from Africa

Only modern H. sapiens in fossil record


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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 Mouth

(S. Africa)

134-74 ka Electron spin resonance

Several individuals; highly fragmentary

Herto (Ethiopia)

160-154 ka 40Ar-39Ar 3 adults, one child


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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 than

among Neandertals


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Upper Paleolithic symbol and ritual

Le Chauvet (30 ka)

Lascaux (17 ka)

Hohle Fels (30 ka)

Venus of Willendorf(25 ka)

Ivory horse fromVogelherd, 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 meaningSymbols 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)


All rights reservedSource: McBrearty and Brooks (2000) Journal of Human Evolution 39:453-563

X


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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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• 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 lineage


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• What is the replacement theory?


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• What is the replacement theory?– Homo erectus spread throughout world, 1-2 million

years ago– Anatomically modern humans left Africa ~150,000-

200,000 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?

– 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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100% 0%25%

Continuity with no gene flow

Strict Out of Africa(complete replacement)

Percentage of local, archaic admixture in first modern humans in Eurasia

Debate centers onthis range of admixture

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 ~100-200kya – 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

Africa

Africa

AsiaEurope

Europe Asia

Past

Present

Time

“Modernhumans”

“Archaichumans”

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

• Substantial disparities in life and death

• Persistence of racial-genetic determinism in biomedicine

• Opportunity to advance anthropological critique of race

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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





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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 diversityTotal 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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• 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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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, Ukraine; YG, Yugoslavia. (Novembre et al. Nature, 2008)


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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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