Hum evolgen2011 scatterlingsofafrica


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Lecture on Bio380 module at University of Birmingham on Recent African Origins theory and the evidence for it.

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Hum evolgen2011 scatterlingsofafrica

  1. 1. Scatterlings of Africa Bio380 Human Evolution Genes and Genomes Professor Mark Pallen, University of Birmingham
  2. 2. Africa: Cradle of Humanity? <ul><li>Charles Darwin: Origin of Species 1859 </li></ul><ul><ul><li>“ Light will be thrown on the origin of man and his history” </li></ul></ul><ul><li>Charles Darwin: Descent of Man 1871 </li></ul><ul><ul><li>speculated that humans originated in Africa </li></ul></ul><ul><ul><li>“ In each great region of the world the living mammals are closely related to the extinct species of the same region. It is, therefore, probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man's nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere.” </li></ul></ul>
  3. 3. The focus moves from Africa <ul><li>Archaic fossil humans found in </li></ul><ul><ul><li>Asia (Java Man 1891, Peking Man 1921) </li></ul></ul><ul><ul><li>Europe (Neanderthal 1856, Heidelberg 1907, Piltdown* 1912) </li></ul></ul><ul><li>Early theories </li></ul><ul><ul><li>Multiregionalism (Weidenreich 1930s) H. erectus turned into H. sapiens everywhere, but populations retained local “racial” features” </li></ul></ul><ul><ul><li>Long cryptic “pre- sapiens ” lineage, separate from archaic forms </li></ul></ul><ul><ul><li>Pre-Neanderthal ancestor (based on Tabun, Skhul fossils) </li></ul></ul>
  4. 4. Africa: Cradle of Humanity redux <ul><li>Earliest hominid fossils found in Africa (Toumai, Orrorin , Ardipithecus , Australopithecus ) </li></ul><ul><li>Earliest Homo erectus / ergaster fossils from Africa (~1.9Mya) </li></ul><ul><li>But fossils from Georgia and Java dating to ~1.8Mya suggest early spread: “Out of Africa I” </li></ul><ul><li>But where and how did Homo sapiens originate? </li></ul>
  5. 5. Coon’s candelabra <ul><li>US anthropologist Carleton Coon (1962) posited five separate lineages evolving in parallel from H. erectus </li></ul><ul><ul><li>“ If Africa was the cradle of mankind, it was only an indifferent Kindergarten. Europe and Asia were our principal schools ” </li></ul></ul><ul><li>American Loring Brace added “Neanderthaloid phase” </li></ul><ul><li>Spectrum hypothesis: blending of modern and archaic characteristics </li></ul>Capoid Negroid Caucasoid Australoid Mongoloid Dispersal of H. erectus from Africa ~1.9Ma
  6. 6. Competing theories from 1970s onwards <ul><li>Recent African Origin (RAO) or “ Out of Africa” </li></ul><ul><ul><li>Chris Stringer suggests Homo erectus evolved into Homo sapiens in Africa, and then only recently (<200 Kya) ventured out of Africa and dispersed around the world, replacing any existing H. erectus or H. neanderthalensis populations (note distinction between OOA1 and OOA2) </li></ul></ul><ul><li>Modern Multi-regionalism </li></ul><ul><ul><li>Milford Wolpoff suggests that Homo erectus evolved into modern humans in several different locations through out the world, with continuity of gene flow between ancient H. erectus and modern human populations </li></ul></ul>
  7. 7. Stringer 1974: cranial shape suggests Neanderthals are not good ‘ancestors’ - there are better ones, esp. in Africa
  8. 8. How can we test the hypotheses? Predictions.... <ul><li>Fossil Record </li></ul><ul><ul><li>multiregionalism: oldest human fossils could be anywhere </li></ul></ul><ul><ul><li>RAO: oldest human fossils will be found in Africa; cultural universals </li></ul></ul><ul><li>Geographical distribution of genetic diversity </li></ul><ul><ul><li>multiregionalism: greatest diversity could be anywhere </li></ul></ul><ul><ul><li>RAO: greatest diversity will be in Africa </li></ul></ul><ul><li>Molecular phylogenetics </li></ul><ul><ul><li>multiregionalism: MRCA anywhere; RAO: MRCA in Africa </li></ul></ul>
  9. 9. Fossil Record <ul><li>Earliest AMH fossils are from Africa </li></ul><ul><ul><li>Omo Kibush 1 Ethiopia 195 Kya </li></ul></ul><ul><ul><li>Herto Ethiopia 154-160 Kya </li></ul></ul><ul><li>Oldest AMH fossils outside Africa much younger </li></ul><ul><ul><li>Skhul, Qafzeh, Palestine, 80-120 Kya </li></ul></ul><ul><ul><li>Mungo, Australia, 42 Kya </li></ul></ul><ul><ul><li>Tianyuan, China, 38-42 Kya </li></ul></ul><ul><ul><li>Peștera cu Oase, Romania, 40.5 Kya </li></ul></ul>White TD, Asfaw B, DeGusta D, Gilbert H, Richards GD, Suwa G, Howell FC (June 2003). &quot;Pleistocene Homo sapiens from Middle Awash, Ethiopia&quot;. Nature 423 (6941): 742–7 McDougall, I.; Brown, F. H.; Fleagle, J. G. (2005), &quot;Stratigraphic placement and age of modern humans from Kibish, Ethiopia&quot;, Nature 433 (7027): 733–736
  10. 10. Geographical distribution of diversity Africa Asia Europe 79 RFLPs 30 microsatellites beta-globin flanking region Xq13.3 50 autosomal segments mtDNA control region 43 Y-chr binary markers From Human Evolutionary Genetics: Origins, Peoples & Disease, p 251 Jobling, Hurles, Tyler-Smith 0.29 0.33 0.38 0.81 0.68 0.73 0.32% 0.33% 0.23% 0.035% 0.025% 0.034% 0.11 0.06 0.06 2.1 1.75 1.1 0.84 0.90 0.85
  11. 12. Allozyme polymorphisms in multiple loci (Cavalli-Sforza and Feldman 2003)
  12. 13. Molecular Phylogenetics <ul><li>Mitochondrial DNA analysis (mtDNA) </li></ul><ul><ul><li>Maternally inherited, therefore telling the story from the female side of human history </li></ul></ul><ul><li>Y Chromosome analysis </li></ul><ul><ul><li>Inherited down the paternal line, complementing mtDNA </li></ul></ul><ul><li>But most recent common ancestor far more recent than mtDNA and Y chromosomes MRCAs </li></ul><ul><ul><li>in 15,000 years you will be the ancestor of everyone or of no one! </li></ul></ul>
  13. 14. Mitochondrial Eve The first glimpse <ul><li>Cann et al 1987 </li></ul><ul><ul><li>analysed mtDNA from 147 individuals using 12 restriction enzymes </li></ul></ul><ul><ul><li>constructed tree and date tree using mtDNA mutation rate </li></ul></ul><ul><ul><li>root in Africa; ~200 (140-290) Kya </li></ul></ul><ul><ul><li>“ all these mitochondrial DNAs stem from one woman who is postulated to have lived about 200,000 years ago, probably in Africa” </li></ul></ul><ul><ul><li>“ African Eve” </li></ul></ul><ul><li>Criticisms </li></ul><ul><ul><li>18/20 “African” mtDNA samples came from African-Americans </li></ul></ul><ul><ul><li>methodology not ideal </li></ul></ul><ul><ul><li>mid-point rooting rather than use of outgroup </li></ul></ul><ul><ul><li>Mitochondrial Eve was not the only female of her time!! </li></ul></ul>
  14. 15. <ul><li>53 individuals, complete mtDNA (minus highly variable region), used 32 “real” Africans </li></ul><ul><li>complete separation of African and non-African lineages </li></ul><ul><li>three exclusively African branches </li></ul><ul><li>African branches deep; others “star-like” </li></ul><ul><li>TMRCA for all: 172 KYA </li></ul><ul><li>TMRCA for main non-African/African branch 52Kya </li></ul>
  15. 16. Mitochondrial Eve All non-African lineages derive from two branches, M and N, from L3 haplogroup
  16. 17. Y chromosomal data X Y Male Female X X Y chromosome is paternally inherited “ Y Adam” was also African ~60,000 years ago But not the only male of his time and a moving target, shifting forward as Y lines die out Europeans Asians Africans
  17. 18. Y chromosomal data All non-African lineages derive from CR haplogroup
  18. 19. T. Michael Keesey (CC BY 2.0)
  19. 20. The peopling of the world 100-150Kya 60Kya 45Kya 50Kya 15Kya N D Beachcomber route Remote Australia colonised before Europe!
  20. 21. African Exodus movement of beach-combing people? <ul><li>small group of humans living in East Africa migrated north east, crossing the Red Sea and went on to populate the rest of the world </li></ul><ul><li>today at Gate of Grief Red Sea about 12 miles wide, but 50 Kya was much narrower and sea levels were 70m lower </li></ul><ul><li>straits were never completely closed, there may have been islands in between which could be reached using simple rafts. </li></ul><ul><li>fresh water springs along coast when sea level lower </li></ul><ul><li>shell middens 125Kya in Eritrea indicate the diet of early humans was sea food obtained by beach-combing. </li></ul>
  21. 22. migration speed for the first Eurasians of 0.7 to 4 km per year rough upper estimate of the number of women who left Africa 60,000 years ago: ~600
  22. 23. Other Evidence Of Microbes and Man <ul><li>Human gut bacterium Helicobacter pylori </li></ul><ul><ul><li>Causes gastritis, peptic ulcers and gastric cancer </li></ul></ul><ul><ul><li>Passed from mother to children (similar to mtDNA) </li></ul></ul><ul><ul><li>Little human-to-human horizontal transmission </li></ul></ul><ul><li>H. pylori and human evolutionary histories are congruent </li></ul><ul><ul><li>Can be used to infer human pre-history </li></ul></ul><ul><ul><li>High mutation rate, so H. pylori DNA sequences are more informative about the human past than human DNA </li></ul></ul>
  23. 24. (see also Disotell 2003 Genome Biol. )
  24. 26. Other Evidence Of Lice and Men <ul><li>Darwin letter to Henry Denny, 1865 </li></ul><ul><ul><li>“ Will you excuse me asking you to inform me whether the Chiloe pediculi form a distinct species or well-marked variety? Is it the case that the Lice differ on different races of man; & can you believe, from any other evidence which you may possess, the statement by Mr Marshall about the Polynesian lice not living on a distinct race of man?” </li></ul></ul>
  25. 29. Conclusions <ul><li>Anatomically modern humans appeared first in Africa </li></ul><ul><li>Genetic diversity for most loci higher in Africa </li></ul><ul><li>Most phylogenies of individual loci show root in Africa </li></ul><ul><ul><li>especially mitochondrial Eve and Y Adam </li></ul></ul><ul><li>Evidence from human DNA, lice and microbes consistent with RAO, but also with some archaic admixture </li></ul>
  26. 30. Current consensus? 100% RAO | RAO+hybridisation | assimilation | multiregionalism | 0% RAO
  27. 31. Old racist view View from modern genetics Genetic Residues of Ancient Migrations: An End to Biological Essentialism and the Reification of Race William M. Richman University of Toledo
  28. 32. Conclusions Hdptcar Attribution 2.0 Generic (CC BY 2.0) Dennis Stefani, (c) Mrs. Me, Inc., 2008, made available under a CCBY-NC-ND license Helga's Lobster Stew Attribution 2.0 Generic (CC BY 2.0) Steve Evans Attribution 2.0 Generic (CC BY 2.0) Publik15 Attribution 2.0 Generic (CC BY 2.0) We are all no more than 4000 mothers away from Africa
  29. 33. Recommended Viewing & Listening See also: Genomic Dub Collective Origin of Species in Dub I’m a African, I’m a African And I know what’s happenin’ I’m a African, I’m a African Archaeologists know what’s happenin’ You a African? You a African? Do you know what’s happenin’? I’m a African, I’m a African Geneticists know what’s happenin’   No I wasn’t born in Ghana but Africa is my mama ‘ Cause that’s where my mama got her mitochondria You can try to fight if you wanna, but it’s not gonna change me ‘ Cause it’s plain to see, Africans are my people And if it’s not plain to see then your eyes deceive you I’m talkin’ primeval; the DNA in my veins Tells a story that reasonable people find believable But it might even blow your transistors; Africa is the home of our most recent common ancestors Which means human beings are all brothers and sisters So check the massive evidence of Homo erectus And Australopithecus afarensis in the fossil record And then try to tell me that we’re not all connected The fossil record has gaps but no contradictions And it complements the evidence in your chromosomes So I came to let you know about your ancestral home.
  30. 34. Recommended Reading <ul><li>See online archive </li></ul><ul><li>The Incredible Human Journey , Alice Roberts </li></ul><ul><li>Origin of our Species, Chris Stringer </li></ul><ul><li>And if you want to buy a textbook: </li></ul><ul><ul><li>Human Evolutionary Genetics, Origins, Peoples and Disease Jobling, Hurles, Tyler -Smith </li></ul></ul>