Theory of Evolution and Genetics

Chapter

Abstract

The main purpose of this contribution is to document the role of natural selection, a major factor in Darwinian evolution which is difficult to dissect specially in the case of human evolution. Recent major steps in human genetics can be summarized as follows: (a) the complete sequence of the human genome; (b) the Single Nucleotide Polymorphisms (SNP) discovery and characterization; (c) the HapMap Project; (d) the Human Genome Diversity Project (HGDP)-CEPH set-up of 1,000 world-wide cell lines publicly available; (e) the 1,000 genomes project; (f) The very recent draft DNA sequence of the Neanderthal Genome. An interesting advance from HGDP-CEPH genome-wide analyses on genetic diversity and population structure at the world-wide level (high resolution from technological advance allowing to type more than 500,000 SNP per individual) has been to resolve migration from adaptation and natural selection. The tests of selection used were: (a) iHS – detection of partial sweeps in the genome scenario from haplotype patterns; and, more traditionally, (b) Fst – differentiation of gene frequencies, calculated either globally or between broad geographic regions. Interestingly enough, the color of the skin problem originally pointed out by Charles Darwin in The Descent of Man, and Selection in Relation to Sex. p. 381, 1981 facsimile edition by Princeton University Press, has been elucidated by finding some related traits (SLC24A5, KITLG, MC1R) whose world geographic distribution shows how natural selection and geographic barriers are interacting. What makes us humans? The draft sequence of the Neanderthal genome (Green et al. 2010) surprisingly shows that the Neanderthal DNA signal can be found not only in the genomes of Europeans, but also in people from East Asia and Papua New Guinea, where Neanderthals never lived. Even more of interest, a catalogue of features unique to the human genome has been pointed out. Five genes affected by two substitutions that either change aminoacids or introduce a stop codon, and that have become fixed among humans since the divergence from Neanderthals have been identified. The start codon in the gene TRPM1 that is present in Neanderthals and chimpanzees has been lost in some present-day humans. The TRPM1 encode melastatin, an ion channel important for maintaining melanocyte pigmentation in the skin. It is intriguing that skin-expressed genes comprise three out of six genes that either carry multiple fixed substitutions changing amino acids or in which a start or stop codon has been lost or gained. This suggests that selection on skin morphology and physiology may have played an important role on the hominin lineage. The finding of 20 top candidate selective sweep regions adds further evidence on how the present technological advances are instrumental for resolving cases of natural selection in humans too elusive to be found by traditional genetic tools: the case of skull structure (cleidocranial dysplasia and RUNX2 gene) is mentioned. Eventually a challenging topic worth of further analyses, the sexual selection in humans, has been quoted from Charles Darwin in The Descent of Man, and Selection in Relation to Sex, pp. 605–606: in fact, his prophetical thinking has not been yet fully explored: “We cannot positively say that this character, but not that, has been thus modified; it has, however, been shown that the races of man differ from each other and from their nearest allies, in certain characters which are of no service to them in their daily habits of life, and which it is extremely probable would have been modified through sexual selection”.

References

  1. 1.
    Cann H et al (2002) A human genome diversity cell panel. Science 296:261–262PubMedCrossRefGoogle Scholar
  2. 2.
    Darwin CR (1859) On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life, 1st edn. John Murray, LondonGoogle Scholar
  3. 3.
    Darwin CR (1871/1874) The descent of man and selection in relation to sex, 2nd edn. John Murray, London, pp 605–606Google Scholar
  4. 4.
    Darwin CR (1981) The descent of man and selection in relation to sex. Princeton University Press, Princeton, p 381 [1871 facsimile edition]Google Scholar
  5. 5.
    Darwin CR, Wallace AR (1858) On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. Proc Linn Soc Lond Zool 3:46–50Google Scholar
  6. 6.
    Green RE, Malaspinas AS, Krause J et al (2008) Complete Neanderthal mitochondrial genome sequenced determined by high-throughput sequencing. Cell 134:416–426PubMedCrossRefGoogle Scholar
  7. 7.
    Green RE, Krause J, Briggs AW et al (2010) The draft sequence of the Neanderthal genome. Science 328:710–722PubMedCrossRefGoogle Scholar
  8. 8.
    Human Genome Project Information (s.d.) http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml
  9. 9.
    International HapMap Project (s.d.) http://snp.cshl.org/
  10. 10.
    Kidd JM, Cooper GM, Donahue WF et al (2008) Mapping and sequencing of structural variation from eight human genomes. Nature 453:56–64PubMedCrossRefGoogle Scholar
  11. 11.
    Li JZ et al (2008) Worldwide human relationships inferred from genome-wide patterns of variation. Science 319:1100–1104PubMedCrossRefGoogle Scholar
  12. 12.
    Novembre J, Di Rienzo A (2009) Spatial pattern of variation due to natural selection in humans. Nat Rev Genet 10:745–755PubMedCrossRefGoogle Scholar
  13. 13.
    Pickrell JK, Coop G, Novembre J et al (2009) Signals of recent positive selection in a worldwide sample of human populations. Genome Res 19:826–837PubMedCrossRefGoogle Scholar
  14. 14.
    Roach M (2005) Roots of desire: the myth, meaning and sexual power of red hair. Bloomsbury, New YorkGoogle Scholar
  15. 15.
    The 1000 Genomes Project (s.d.) www.1000genomes.org
  16. 16.
    The 1000 Genomes Project, Consortium (2010) A map of human genome variation from population-scale sequencing. Nature 467:1061–1073CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Italia S.r.l.  2012

Authors and Affiliations

  1. 1.Department of Genetics, Biology and BiochemistryUniversity of Turin and Human Genetics Foundation (HuGeF)TurinItaly

Personalised recommendations