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How do we know?: Who are the closest living relatives of humans? How do we know? Bonobo Chimp Gorilla Orang Where are they now?: Where are they now? Orangs Gorillas Chimps Bonobos Early evidence: immunology: Early evidence: immunology Mitochondrial gene phylogeny: Mitochondrial gene phylogeny Why might different genes yield different phylogenies?: Why might different genes yield different phylogenies? 2 3 5 Why might different genes yield different phylogenies?: Why might different genes yield different phylogenies? What was the common ancestor like?: What was the common ancestor like? Recent human phylogeny (best guess): Recent human phylogeny (best guess) Do we share genes with Neanderthals or Homo erectus?: Do we share genes with Neanderthals or Homo erectus? mtDNA from Neanderthal Relationships among contemporary humans: mitochondrial DNA: Relationships among contemporary humans: mitochondrial DNA Europe, Asia, Australia Asian / Australian African Interpretation of mitochondrial DNA evidence: Interpretation of mitochondrial DNA evidence Did we have one female ancestor in the last 200,000 years? Methods to determine ancestry: coalescent: Methods to determine ancestry: coalescent Common ancestry and genetic markers: Common ancestry and genetic markers Genetic study of human traits: Genetic study of human traits Brain size – two loci of interest microcephalin (MCPH1) Abnormal spindle-like microcephaly associated (ASPM) Selected? ASPM and selection: ASPM and selection Ka / Ks McDonald-Kreitman test fixed polymorphic replacements 19 6 silent 7 10 Evans et al 2004 Distribution of ASPM: Distribution of ASPM Mekel-Bobrov et al 2005. Haplotype: 62kb Microcephalin and selection?: Microcephalin and selection? Wang and Su 2004. Ka / Ks Microcephalin distribution: Microcephalin distribution Evans et al 2005 Haplotype: 29 kb Microcephalin origins: Microcephalin origins Evans et al 2006 Relationships among human populations: Fst: Relationships among human populations: Fst Evolution and races: Evolution and races When did we stop being furry? How to know? . . . Evolution and races: Evolution and races Evolution and races: natural selection on skin colour: Evolution and races: natural selection on skin colour Genetic Basis of Human Skin Colour: Genetic Basis of Human Skin Colour Partially known – one of ~6 loci identified Melanocortin 1 receptor (MC1R) Unusual pattern of sequence diversity Human genetic diversity: Human genetic diversity Forces acting on human populations: Forces acting on human populations Sexual selection and humans: Sexual selection and humans Diamond, 1992 Sexual selection and humans: Sexual selection and humans Diamond, 1992 References: References Currat, M. et al. 2006. Comment on 'Ongoing adaptive evolution of ASPM' and 'Microcephalin, a gene regulating brain size'. Science 313:172a. Diamond, J. 1992. The third chimpanzee. HarperCollins. Evans, P. D. et al. 2004. Adaptive evolution of ASPM, a major determinant of cerebral cortical size in humans. Human molecular genetics 13:489-494. Evans, P. D. et al. 2005. Microcephalin, a gene regulating brain size, continues to evolve adaptively in humans. Science 309:1717-1720. Evans, P. D. et al. 2006. Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage. PNAS 103:18178-18183. Jablonski, N. G. and Chapin, G. 2000. The evolution of human skin coloration. Journal of human evolution 39: 57-106. Kittler, R. et al. 2003. Molecular evolution of Pediculus humanus and the origin of clothing. Current Biology 13:1414-1417. McKee, J. K. et al. 2005. Undertanding human evolution (5th ed.) Pearson Prentice Hall. Mekel-Bobrov, N. et al. 2005. Ongoing adaptive evolution of ASPM, a brain size determinant in Homo sapiens. Science 309: 1720-1722. Rosenberg, N. A. et al. 2002. Genetic structure of human populations Science 298: 2381-2385. Templeton, A. 2002. Out of Africa again and again. Nature 416:45-51. Varki and Altheide. 2005. Comparing the human and chimpanzee genomes: searching for needles in a haystack. Genome research 15:1746-1758. Wang, Y and Su, B. 2004. Human molecular genetics 13: 1131-1137. Study questions: Study questions Explain lineage sorting. Why is it more likely to occur with relatively short times between speciation events? How might this explain different results for different genes for the human/chimp/gorilla relationships? Is it accurate to say that humans evolved from chimps? Why or why not? In a study of Old World monkeys (Hayasaka et al. 1996) three individual rhesus macaques that were studied did not form a monophyletic group. Instead, one of the rhesus macaques had mtDNA more closely related to Japanese and Taiwanese macaques (which are different species). Give at least two hypotheses explaining this. Different ethnic groups within Africa are more genetically distinct from each other than all other ethnic groups combined. Explain why this might be the case. Does the root of the human mtDNA tree in Africa imply that there was a single female alive 200,000 years ago? Explain. Study questions: Study questions 6. The human Y-chromosome tree appears younger than the human mtDNA tree. Does this mean that females evolved before males? Would skin color be a good trait to use for human phylogeny? Explain empirically (using data on the relationships of human populations) and theoretically (the role of traits under strong selection in phylogeny reconstruction). Are hypotheses of sexual selection shaping human anatomy scientific? Describe the role of each evolutionary force in human evolution. What do studies of chimps and bonobos tell us about human nature? What are the limits of these studies? You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.