David Reich (geneticist)

David Reich is a geneticist whose research focusses on finding complex genetic patterns that cause susceptibility to common diseases among large populations. He is professor in the department of genetics at the Harvard Medical School, and an associate of the Broad Institute,

Academic career

David Reich is a geneticist and professor in the department of genetics at the Harvard Medical School, and an associate of the Broad Institute, whose research studies comparing human DNA with that of chimpanzees, Neanderthals and Denisovans.

Reich's genetics research focuses primarily on finding complex genetic patterns that cause susceptibility to common diseases among large populations, rather than finding specific genetic flaws associated with relatively rare illnesses.

Genetic research

Split of chimpanzees and humans (2006)

Reich's research team at Harvard University has produced evidence that, over a span of at least four million years, various parts of the human genome diverged gradually from those of chimpanzees.[1][2] The split between the human and chimpanzee lineages may have occurred millions of years later than fossilized bones suggest, and the break may not have been as clean as commonly thought by modern scientists. The new DNA evidence developed by Reich's team suggests that after the two species initially separated, they may have continued interbreeding for several million years. A final genetic split transpired between 6.3 million and 5.4 million years ago, according to a report on their research published in the science journal Nature.[3]

Harvard anthropologist David Pilbeam calls the new study "terrifically exciting and important work," and commends Reich's method for estimating the time span of human-chimpanzee genetic divergence.

Indian population (2009)

Reich's 2009 publication Reconstructing Indian population history[4] was a landmark study in the research on India's genepool and the origins of its population. Reich et al. (2009), in a collaborative effort between the Harvard Medical School and the Centre for Cellular and Molecular Biology (CCMB), examined the entire genomes worth 560,000 single nucleotide polymorphisms (SNPs), as compared to 420 SNPs in prior work. They also cross-compared them with the genomes of other regions available in the global genome database.[5] Through this study, they were able to discern two genetic groups in the majority of populations in India, which they called "Ancestral North Indians" (ANI) and "Ancestral South Indians" (ASI).[note 1] They found that the ANI genes are close to those of Middle Easterners, Central Asians and Europeans whereas the ASI genes are dissimilar to all other known populations outside India.[note 2][note 3] These two distinct groups, which had split ca. 50,000 years ago, formed the basis for the present population of India.[6]

A follow-up stuy by Moorjani et al. (2013) revealed that the two groups mixed between 1,900 to 4,200 years ago (2200 BCE-100 CE), where-after a shift to endogamy took place and admixture became rare.[note 4] Speaking to Fountain Ink, David Reich stated, "Prior to 4,2000 years ago, there were unmixed groups in India. Sometime between 1,900 to 4,200 years ago, profound, pervasive convulsive mixture occurred, affecting every Indo-European and Dravidian group in India without exception." Reich pointed out that their work does not show that a substantial migration occurred during this time.[7]

Metspalu et al. (2011), representing a collaboration between the Estonian Biocenter and CCMB, confirmed that the Indian populations are characterized by two major ancestry components. One of them is spread at comparable frequency and haplotype diversity in populations of South and West Asia and the Caucasus. The second component is more restricted to South Asia and accounts for more than 50% of the ancestry in Indian populations. Haplotype diversity associated with these South Asian ancestry components is significantly higher than that of the components dominating the West Eurasian ancestry palette.[8]

Human genetic map (2011)

He was a co-leader, along with statistician Simon Myers, of a team of genetics researchers from Harvard University and the University of Oxford that in July 2011 revealed their completion of the world's most detailed human genetic map to date.[9]

Interbreeding of Neanderthals and humans (2013)

Reich's research findings that Neanderthals and Denisovans almost certainly interbred with modern humans are less controversial, and in fact have been published widely.[10]

Genetic markers for prostate cancer

Reich's lab has received media attention following its discovery of a genetic marker which is linked to an increased likelihood of developing prostate cancer.

See also

Notes

  1. ↑ Reich et al. (2009) excluded the Austro-Asiatic and Tibeto-Burman speakers from their analysis in order to avoid interference.
  2. ↑ Reich et al. (2009): "We analyze 25 diverse groups to provide strong evidence for two ancient populations, genetically divergent, that are ancestral to most Indians today. One, the "Ancestral North Indians" (ANI), is genetically close to Middle Easterners, Central Asians, and Europeans, while the other, the "Ancestral South Indians" (ASI), is as distinct from ANI and East Asians as they are from each other."
  3. ↑ Moorjani et al. (2013): "Most Indian groups descend from a mixture of two genetically divergent populations: Ancestral North Indians (ANI) related to Central Asians, Middle Easterners, Caucasians, and Europeans; and Ancestral South Indians (ASI) not closely related to groups outside the subcontinent."
  4. ↑ Moorjani et al. (2013): "We report genome-wide data from 73 groups from the Indian subcontinent and analyze linkage disequilibrium to estimate ANI-ASI mixture dates ranging from about 1,900 to 4,200 years ago. In a subset of groups, 100% of the mixture is consistent with having occurred during this period. These results show that India experienced a demographic transformation several thousand years ago, from a region in which major population mixture was common to one in which mixture even between closely related groups became rare because of a shift to endogamy."

References

  1. ↑ ScienceNews.org - 'Hybrid-Driven Evolution: Genomes show complexity of human-chimp split: Not only did the evolutionary parting of human from chimpanzee ancestors occur more recently than had been indicated by previous data, but it also played out over an extended period during which forerunners of people and chimps interbred', Bruce Bower, Science News (May 20, 2006)
  2. ↑ Two Splits Between Human and Chimp Lines Suggested, Nicholas Wade, New York Times (May 18, 2006)
  3. ↑ Patterson, N.; Richter, D. J.; Gnerre, S.; Lander, E. S.; Reich, D. (2006). "Genetic evidence for complex speciation of humans and chimpanzees". Nature 441 (7097): 1103–1108. doi:10.1038/nature04789. PMID 16710306.
  4. ↑ reich 2009.
  5. ↑ Chakravarti, Aravinda (24 September 2009). "Tracing India's invisible lthreads" (PDF). Nature (News & Views).
  6. ↑ Elie Dolgin (2009), Indian ancestry revealed. The mixing of two distinct lineages led to most modern-day Indians, Nature News
  7. ↑ Srinath Perur, The origins of Indians. What our genes are telling us., Fountain Ink
  8. ↑ Metspalu et al. 2011.
  9. ↑ David Cameron (July 20, 2011). "Detail distinguishes map of African-American genomics". Harvard Gazette. Retrieved July 22, 2011.
  10. ↑ Carl Zimmer, "Interbreeding with Neanderthals", Discover, March 2013, pp. 38-44.

Sources

  • Metspalu, Mait; Romero, Irene Gallego; Yunusbayev, Bayazit; Chaubey, Gyaneshwer; Mallick, Chandana Basu; Hudjashov, Georgi; Nelis, Mari; Mägi, Reedik; Metspalu, Ene; Remm, Maido; Pitchappan, Ramasamy; Singh, Lalji; Thangaraj, Kumarasamy; Villems, Richard; Kivisild, Toomas (2011), "Shared and Unique Components of Human Population Structure and Genome-Wide Signals of Positive Selection in South Asia", The American Journal of Human Genetics 89 (6): 731–744, doi:10.1016/j.ajhg.2011.11.010, ISSN 0002-9297 
  • Moorjani, P.; Thangaraj, K.; Patterson, N.; Lipson, M.; Loh, P. R.; Govindaraj, P.; Singh, L. (2013), "Genetic evidence for recent population mixture in India", The American Journal of Human Genetics 93 (3): 422–438, doi:10.1016/j.ajhg.2013.07.006, PMC 3769933, PMID 23932107 
  • Reich, David; Thangaraj, Kumarasamy; Patterson, Nick; Price, Alkes L.; Singh, Lalji (2009), "Reconstructing Indian population history", Nature 461 (7263): 489–494, Bibcode:2009Natur.461..489R, doi:10.1038/nature08365, ISSN 0028-0836, PMC 2842210, PMID 19779445 

External links

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