What are the two major models of human origin and their supporters.txt
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What are the two major models of human origin and their supporters?
- Replacement (out of Africa) supported by Chris Stringer
- Regional continuity (multiregionalism) supported by Milford Wolpoff
- Out of Africa
- AMH evolved in Africa (200-150kya), eventually dispersed out, and replaced archaic Eurasian populations as they met
- No (or minimal) admixture
- Complete replacement
- Older origin of Homo sapiens
- AMH evolved in concert across Eurasia and Africa
- Long-range gene-flow between archaic populations
- No replacement
Not fully AMH, but almost?
- Florisbad, South Africa
- Ngaloba Beds, Tanzania (120 kya)
- KNM-ER 3884, Kenya (270 kya)
- Omo 2 (Kibish), Ethiopia (195 kya)
- Jebel Irhoud, Morocco (130 kya)
Fully, anatomically modern human 195 kya to present?
- Klasies River Mouth, South Africa
- Border Cave, South Africa
- Omo I (Kibish), Ethiopia
- Singa, Sudan
Jebel Irhound 1?
- 130 kya
- Not completely modern, but very close
- Big brow ridge
- Omo I Omo Kibish formation
- Anatomically modern!
- Dated to 195 kya
- Possibly oldest anatomically modern human remains
- Found near Herto village (Middle Awash, Ethiopia)
- Hence known as Herto man
- Dated to 160-154 kya
- Anatomically modern!
- Just outside envelope of present-day variation
- Most similar to an Australian aborigine anatomically
- Named Homo sapiens idaltu by White et al. (2003)
- Idaltu means Elder in the Afar language
- Acheulean and MSA tools
- Discoverers say it evolved anagenetically from Homo rhodesiensis (i.e., Kabwe 1); Textbook calls this African Homo heidelbergensis
- Herto man appears right as classic Neanderthals arise in Europe
- Strong fossil data AGAINST multiregionalism
Klasies River Mouth?
- South African coast caves
- Lots of AMH bones
Skhul and Qafzeh?
- First non-African AMH, ~100 kya
- Found in what is now Israel
- Clearly modern anatomy
- Co-existed with Neanderthals
- Thought to have died off or retreated back into Africa
- Unsuccessful migration
- Region had highly variable climate, often inhospitable
- Serially re-colonized?
- Vertical forehead
- Reduced brow
- Canine fossa
- Definite chin
- Small anterior teeth
- First destination outside of Africa, ~60kya
- Unclear where we entered though
- Precise timing of migration
- Northern Dispersal Route
- Southern Dispersal Route
- No Homo erectus or heidelbergensis known in Australia
- AMH remains from Lake Mungo
- Contentious dating
- As young as ~30kya or as old as ~50kya (Bowler et al. 2003)
- Genetic evidence corroborates 50 kya
- Multiregionalists see East Asian traits as evidence of continuity
- ??smaller face and teeth
- flatter cheeks
- rounder foreheads
- less prominent noses
- shovel-shaped incisors
- However, these traits could be homoplasies
- Product of similar selective forces (specific to E Asia) on both H. erectus and H. sapiens
- Or product of genetic drift
- Additionally, not corroborated by other types of data (e.g., mtDNA or nuclear genome sequence data)
- Les Eyzies, France 32 kya
- Exact migration route into Europe unknown
- Earliest Europeans
- Arrive as Neanderthals on way out
Dolni Vestonici (Moravia)?
- Upper Paleolithic Site
- ca. 30-25,000 years old
- structures, activity areas, burials, grave goods, ritual symbolic behavior
- Mitochondrial DNA (mtDNA) is maternally inherited
- Both males and females inherit it from mother
- Only females pass it on.
- No recombination!
- All modern humans share a mitochondrial common ancestor
- The mitochondrial Eve, 150-200kya in Africa
- Non-Africans are clearly a subset of Africans
Models of Human origins (mtDNA)?
- Clear separation of human mtDNA
- Modern Human-Neanderthal mtDNA divergence ~350-700 kya
- The mtDNA + the timing of earliest African AMH =
- Fact that Homo sapiens and Homo neanderthalensis are separate and sister species
- Advent of the Neanderthal nuclear genome slightly changed the story
- Neanderthal draft genome sequence compared to genomes from:
- the San, the Yoruba, (African)
- the Han Chinese, Papua New Guinea, and France (Non-African)
- Neanderthal genome slightly more similar to non-Africans than Africans
- Not unique to any specific non-African groups
- Later studies with more populations confirmed this
- First estimated 1-4% introgression in non-African genomes
- Draft genome sequenced primarily from Vindija, Croatia (40 kya) and also from Mezmaiskaya (65 kya)
- Higher quality genome from proximal toe phalanx from Denisova cave in the Altai Mountains (>50 kya)
- introgression has been dated 47-65 kya
- Higher introgression found in East Asians than Europeans
- Statistically unclear if South Asians are intermediate or same as Europeans
- Introgression revised to 1.5-2.1% with new sequence data
- Not absolutely clear where introgression occurred
- Denisovans are an unknown populations (or species?) related to Neanderthals
- Little morphological data
- Other than an LM3 and a 5th distal phalanx
- Found in Denisova Cave in Siberia
- Modern Oceanians have 3- 6% Denisovan introgression
End result, models of origin?
- Trace DNA to Africa ~150 kya
- All have different small bits from other places
What this means for out of Africa?
- Replacement model (Out-of-Africa) is regular coffee
- Continuity model (Multiregionalism) is decaffeinated coffee (~10% caffeine content)
- The new Introgression models are like a cup of coffee with ~95% the caffeine of a regular cup
- Can you call that cup regular or decaf?
- Does the name you call it change what it is?
- The name you give it does not matter, it is the numbers that reflect the reality.
Human variation and the race question?
- Homo sapiens is a polytypic species.
- Homo sapiens is genetically homogeneous.
Explaining human diversity?
- 1) Adaptationist Approach
- Variation is a result of natural selection
- 2) Historical Approach
- Variation reflects patterns of population history
Genetic Structure of Human Populations; Rosenberg et al (2002)?
- 377 highly variable regions of the human genome studied
- 1056 individuals from 52 populations worldwide
- ?? Results:
- 93-95% of variation within groups
- 3-5% of variation between groups
- only 8% of alleles regionally exclusive
- of these, median frequency is 1%
Genetic Diversity of Human Populations; Jobling et al?
- Branch lengths proportional to genetic distance
- Space occupied by taxon is proportional to genetic diversity
- Humans genetically homogeneous by hominoid standards
Genetic Diversity of Human Populations; Prunolli?
Diversity as a function of geographic distance
Race: biology or culture?
- Cultural, but conceptualized biologically.
- Blood and race are symbolically intertwined
- Classification schemes serve social purposes
- Race constructed from arbitrary physical characteristics Skin color, hair color, skin, height, etc.
- To function socially, must be categorical and simple
Race vs Ethnicity?
- Conceptions of ethnicity
- temporary & temporal
- Religious & political symbolism
- maintain cultural heritage
- no necessary connection to biological conceptions
- Race and Ethnicity
- Confusion of biology and culture mixing and substitution of terms Ultimately incongruent
Racial Classification Schemes?
- Hypodescent (the one drop rule): classifies into minority group
- racial classification is not fixed (individuals can change it)
- still based on skin tone
- system recognizes more physical variation (500+ race labels)
- class status (money whitens)
- South Africa (Apartheid Era)
- Black, White, Coloured, Indian
- Population Registration, Group Areas Acts (1950)
- Pencil test
Linnaeus: systema naturae?
- (1758) Typological approach to race identifying types within Homo sapiens
- Homo europaeus
- Homo afer
- Homo asiaticus
- Homo americanus
- 5 human races
Earnest a. Hooten?
- American physical anthropologist
- Non-adaptive traits explain real differences between races.
- 3 primary races
- 7 composite races
- 15 sub-races
- 5 races
- Homo sapiens threshold crossed multiple times
- Some races evolved before others
- 9 geographical races
Phenotype and Race?
- Environmental factors
- -temperature ,altitude, sunlight
- Socio-cultural factors
- -diet & nutrition, health care, access to resources
- Geographic proximity
- -positively associated with admixture increasingly unimportant since ~1500
- latitude correlates with darkness of skin
- Lighter skin: ? vitamin D absorption (prevents rickets); ? skin cancer rates & folate depletion
- Darker skin: ? vitamin D absorption (prevents hypervitaminosis D, but risk of rickets at high latitudes); ? rates of sunburn, skin cancer & folate depletion; ? frostbite
- Arctic Peoples = darker than predicted
- Recent arrivals (~10kya)
- Marine diet high in vitamin D
The classificatory conundrum?
- Single traits cant reveal totality of variation
- Multiple traits undermine stable typology
- Different trait lists require new schemes
- Things not measurements
- Rectangular orbit
- Wide interorbital area
- Guttered nasal border
- S shaped zygmatico-maxillary sulture
?How many individuals possess all the features used to describe a racial type?
- European- 35%
- Asian- 51%
- African- 17%
Anthropology and Racism?
- Racial typologies are argued to be biologically rooted
- Biological roots mean existing sociopolitical system is inevitable
- Anthropology has been the formal (academic) arbiter of racial thought
- Disavowal of pure races is due to
- Lots of good data
- Reexamination of old data
- A desire by biological anthropology to repent for past associations
- Cultural anthropologists understood this before biological anthropologists
- Summary denials of population differences are also dangerous
Are we still evolving?
- Cultural adaptation over biological adaptation
- Culture creates novel environments
- Environment still impacts biology
Levels of adaptation?
- Genetic (evolutionary) change
- Time period: generations
- Developmental change
- Time: lifetime/childhood
- Acclimation (acclimatization):
- Plastic physiological change
- Time: minutes/hours/weeks
- Time: unconstrained
- Skin Pigmentation
- Body Shape & Body Size
- Hair Form & Pigmentation
- Skin & Fat
- Skeletal Variation
Inference of adaptation?
- 1. existence of a selective agent (environmental stressor)
- 2. heritability of traits
- 3. covariation of stressors and traits conferring fitness
Circumpolar cold adaptations?
- Different levels of vasoconstriction to the extremities protect against frostbite without losing too much heat
- Cold water fish are high in essential fatty acids (EFAs) which may increase blood pressure in the fingers
- Hypoxia (reduced available oxygen)
- Intense solar radiation
- Low humidity
- Developmental Effects
- Slower maturation
- Greater lung volume Relatively large heart
The Moken Sea Gypsies?
- Adaptation or Acclimatization?
- Normal vision on land, but 2X as clear underwater.
- Other children can be trained to constrict their pupils
- Unclear if the Moken have a genetic adaptation
- Carbohydrate in mammal milk
- Diarrhea, Cramps, Flatulence
- Bacteria!!!Make them do the work
- prevlant in china, south Africa, American Indians, African americans
- ~ 50% of adults have Type II Diabetes Genes
- Thrifty genotype Hypothesis
- adaptation for starvation Environment
- Low incidence in traditional subsistence
- High incidence in affluent environment
- -Health and Illness from distinct perspectives
- 1. Evolution
- 2. Variation
- 3. Genetics
- 1. Quantitative analysis of disease in populations
- 2. Interest in patterns rather than particulars
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