In an intriguing original look at the history of the first Americans, a new study finds evidence that the north-south orientation of the American continents slowed the spread of populations and technology, compared to the east-west axis of Eurasia.
     The research, by Sohini Ramachandran and Noah Rosenberg, from Brown University and Stanford University respectively, uses genetic information to explore the effects of continental axes and climates on human migration and adaptation across the Americas.
     "It has been proposed that the east-west orientation of the Eurasian landmass aided the rapid spread of ancient technological innovations, while the north-south orientation of the Americas led to a slower diffusion of technology there," said Ramachandran. "Our research develops this idea, arguing that continental orientation influenced migration patterns and played an important role in determining the structure of human genetic variation and the distribution and spread of cultural traits."
     To test this hypothesis the team analysed genetic variation data from 68 populations, 39 from Eurasia and 29 from Native Americans. The data were used to identify relationships between the genetic and geographic distances between populations on each continent.
     The research supports the idea that technological diffusion was accelerated across Eurasia because populations with the same latitude experience similar climates, making adaptation to new locations easier, whereas migrating along lines of longitude involves adapting to new climates.

Edited from EurekAlert! (21 September 2011), Past Horizons (3 October 2011)