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 has generated controversy. Dr. 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.
Reich's research team at Harvard University has produced controversial evidence that, over a span of at least four million years, various parts of the human genome diverged gradually from those of chimpanzees. 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.[1]
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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 prestigious science journal Nature.
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.
The hybridization hypothesis "pushes the limits of credulity," according to anthropologist Jeffrey H. Schwartz, who has compiled a great deal of evidence linking human anatomical morphology to that of orangutans. Reich's team looked for data to support an assumption of close genetic ties between humans and chimps, but skimmed over evidence of human similarities to other primates, Schwartz says. Although Schwartz sees no merit in the fact that the new findings appear to solidify the evidence of mankind's relatively recent intermingling with chimpanzees, the new evidence also offers tantalizing hints that hybridization events up to ten million years ago may have introduced significant amounts of DNA from gorilla and orangutan lineages.
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.