https://www.nytimes.com/2019/01/17/magazine/ancient-dna-paleogenomics.html
I encourage you to read the whole thing. A few interesting bits that I think are relevant to recent discussions on this board:
"After abandoning medical school at Harvard for a postdoc at M.I.T., Reich returned to Harvard to establish his own medical-genetics lab. His chief interest lay in the effort to design novel statistical approaches to better explain how populations were related to one another. He showed, for example, on the basis of contemporary genetic data, that modern Indians are in fact a product of two highly distinct groups, one that had been on the subcontinent for thousands of years and another that formed more recently."
"Reich’s analysis helped demonstrate that most living humans, with the general exception of sub-Saharan Africans, have some Neanderthal ancestry."