University News

Research bolsters migration theory

Contributing Writer

Jared Diamond’s 1998 Pulitzer Prize-winning “Guns, Germs and Steel” introduced the notion that the axial orientation of the continents significantly affected the course of human history. Now, a Brown researcher has put that hypothesis to the test — and found good evidence for its validity.

Diamond hypothesized that Eurasia’s east-west orientation allowed freer movement of people and animals than did the Americas’ north-south orientation because of the greater climate variability when moving north to south. This gave Eurasia an advantage in the spread and development of technology.

In a Sept. 13 article in the American Journal of Physical Anthropology, Sohini Ramachandran, assistant professor of biology, and Noah Rosenberg, an associate professor of biology at Stanford University, report on data from 678 sites in the human genome exhibiting a high level of genetic variance. These sites provide information about genetic similarities and differences between populations in the Americas and in Eurasia. The researchers studied how geographical variables, such as latitude and longitude, affected these variations.

Their results show greater genetic differentiation of people in the Americas, indicating a lower rate of migration. “If two populations remain isolated, then they have an opportunity to diverge in their patterns of genetic variation over time,” Rosenberg said.

Assuming migration of human populations is accompanied by the migration of technology, the research provides evidence that the continental axes were factors in the differing rates of technological diffusion in the Americas and Eurasia.

“If people were migrating less frequently from north to south in the Americas compared to east to west in Eurasia, then it’s reasonable to suppose that technologies that people would have been bringing with them also traveled at a slower rate in the Americas,” Rosenberg said.

Ramachandran said she currently has no plans to build on the research.