Human

1
Human
Evolution
What were our ancestors like?
Where did we evolve? Why big brains? Relationship
s between populations?
2
Who are the closest living relatives of humans?
How do we know?
Chimp
Gorilla
Orang
Bonobo
3
Where are they now?
Orangs
Gorillas
Chimps
Bonobos
4
Early evidence immunology
5
Mitochondrial gene phylogeny
6
Why might different genes yield different
phylogenies?
2
3
5
7
Why might different genes yield different
phylogenies?
8
What was the common ancestor like?
9
Recent human phylogeny (best guess)
10
Do we share genes with Neanderthals or Homo
erectus?
mtDNA from Neanderthal
11
Relationships among contemporary humans
mitochondrial DNA
Europe, Asia, Australia
Asian / Australian
African
12
Interpretation of mitochondrial DNA evidence

• Did we have one female ancestor in the last
  200,000 years?

13
Methods to determine ancestry coalescent
14
Common ancestry and genetic markers
15
Genetic study of human traits

• Brain size two loci of interest
• microcephalin (MCPH1)
• Abnormal spindle-like microcephaly associated
  (ASPM)
• Selected?

16
ASPM and selection
Ka / Ks
McDonald-Kreitman test fixed polymorphic replac
ements 19 6 silent 7 10
Evans et al 2004
17
Distribution of ASPM
Haplotype 62kb
Mekel-Bobrov et al 2005.
18
Microcephalin and selection?
Ka / Ks
Wang and Su 2004.
19
Microcephalin distribution
Haplotype 29 kb
Evans et al 2005
20
Microcephalin origins
Evans et al 2006
21
Relationships among human populations Fst
22
Evolution and races

• When did we stop being furry? How to know? . . .

23
Evolution and races
24
Evolution and races natural selection on skin
colour
25
Genetic Basis of Human Skin Colour

• Partially known one of 6 loci identified
• Melanocortin 1 receptor (MC1R)
• Unusual pattern of sequence diversity

26
Human genetic diversity
27
Forces acting on human populations
28
Sexual selection and humans
Diamond, 1992
29
Sexual selection and humans
Diamond, 1992
30
References

• Currat, M. et al. 2006. Comment on Ongoing
  adaptive evolution of ASPM and Microcephalin, a
  gene regulating brain size. Science 313172a.
• 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
  13489-494.
• Evans, P. D. et al. 2005. Microcephalin, a gene
  regulating brain size, continues to evolve
  adaptively in humans. Science 3091717-1720.
• 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 10318178-18183.
• 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 131414-1417.
• 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 41645-51.
• Varki and Altheide. 2005. Comparing the human
  and chimpanzee genomes searching for needles in
  a haystack. Genome research 151746-1758.
• Wang, Y and Su, B. 2004. Human molecular
  genetics 13 1131-1137.

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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.

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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?