In other words, humans have been continuing to evolve in Europe and the Middle East for the last 10,000 years, with significant effect. Reich's paper broadly substantiates the thesis of Gregory Cochran and Henry Harpending's The 10,000 Year Explosion: How Civilization Accelerated Human Evolution. Civilization hasn't ended biological evolution, but proceeds alongside it. 

Reich's genome-wide association study (GWAS) indicates that West Eurasians have increased or reduced their vulnerability to a variety of ailments. Genetic changes have rendered them less susceptible to leprosy, rheumatoid arthritis, bipolar disorder, and schizophrenia, and moreso to coeliac disease and gout. At the same time, there has been positive selection for fair skin, red hair, and intelligence, and negative selection for male-pattern baldness. In summary, West Eurasians have grown foxier, as the arc of their genetic history bends toward fluffy ginger genius. 

Reich's conclusions are pretty likely to hold water. Too many scientific and social scientific fields have been affected by the irreproducibility crisis of modern science. The worst-hit disciplines use far too loose a definition of statistical significance, p?< 0.05.="" genome-wide="" association="" studies,="" by="" contrast,="" tend="" to="" use="" the="" extraordinarily="" tighter="" standard="" of="">< 5="" ×?10^="" −8.="" reich="" lab's="" research="" includes="" a="" variety="" of="" different="" standards="" of="" statistical="" significance,="" including="" some="" that="" are="" only="" of="">< 8.9="" ×?10^="" −5.="" that="" standard="" is="" orders="" of="" magnitude="" more="" reliable="" than="" most="">

The data Reich's lab can work with, after all, is remarkably bounteous. As the researchers wrote:

[W]e increased power through a 14-fold increase in sample size, driven by 10,016 ancient individuals for whom we report new data, which combined with previously reported data yields a dataset of 15,836 people spanning 18,000 years … The final dataset included 8,074,573 SNPs [single-nucleotide polymorphisms] and 1,665,051 insertions or deletions (indels) on chromosomes 1–22. 

Science only can advance on sure foundations when you're reasonably likely the research will hold up. Sociology, psychology, any discipline where you cannot work with millions of pieces of data, cannot be expected to match GWAS levels of rigorous statistical significance. But, as many scientists have proposed, p < 0.01="" or="" p="">< 0.005="" are="" not="" impossible="" goals,="" even="" for="" disciplines="" less="" rich="" in="" data.="" reich's="" peers="" in="" other="" disciplines="" should="" look="" at="" his="" work="" and="" consider="" the="" benefits="" of="" reasonable="" certainty="" that="" a="" paper="" you="" publish="" actually="" says="" something="">

Americans in general might also take Reich's work as a prompt to reconsider our various moratoria on using American Indian biological data to provide gene samples. Reich's report on West Eurasian genetic data presumably is only a beginning. We may expect reports to come on East Eurasians, Sub-Saharan Africans, Aboriginal Australians, Khoisan in South African, American Indians in Latin America—reports on people all over the world.

Except on the American Indians of the United States.

Our legal, regulatory, and cultural inhibitions mean that there will be an enduring blank spot in the knowledge we gain from the genetics revolution—knowledge which will aid not only paleogenetic research but also advances in medicine tailored to each individual's DNA. American Indians might be the last people on Earth to benefit from such advances in genetically individuated medicine if we continue to veto researchers' use of American Indian genetic and paleogenetic data.