Continental America's Orientation Prevented Human Development

A collaboration of researchers from the Stanford University and the Brown University discovered in a new genetic analysis that the development of populations in the Americas was slowed down compared to that of people in Europe and Asia due to the continent's geographical position and orientation.

Experts speculate that people who left Africa tens of thousands of years ago traveled through Europe and Asia mostly along east-west axis, following a similar climate pattern. This type of movement naturally fostered the development and spread of technologies and ideas.

But while this could be achieved in Eurasia, due to its widespread plains and relatively few insurmountable natural obstacles, the situation grew dire for the Americas, and especially the southern part of the continent.

Throughout this area, the new genetic analysis uncovered, climate varied widely from one adjacent region to the next. Furthermore, the continent is largely oriented from north to south, which meant increased levels of adversity towards humans who arrived there 20,000 to 40,000 years ago.

In order to arrive at these conclusions, evolutionary biologists from the two universities carried out a comprehensive survey of more than 700 locations, covering a total of 68 populations. One of the results that immediately stood out was the fact that technology appeared to have spread slower there.

This was largely the result of fewer interactions and cultural exchanges between native groups. The researchers carried out the research by comparing genetic marker data collected from Europe to those collected from the Americas.

“If a lack of gene flow between populations is an indication of little cultural interaction, then a lower latitudinal rate of gene flow suggested for North American populations may partly explain the relatively slower diffusion of crops and technologies through the Americas when compared with the corresponding diffusion in Eurasia,” the team writes.

Details of the new work appear in the latest issue of the esteemed American Journal of Physical Anthropology. “Our understanding of the peopling of the Americas will be refined by archaeological data and additional genetic samples,” Sohini Ramachandran explains.

“But this is the signature of migration we see from genetic data,” adds the expert, who is an assistant professor of biology in the Brown Department of Ecology and Evolutionary Biology. He is also the lead author of the new paper accompanying the study.

“When populations do not share migrants with each other very often,” Rosenberg explained, “their patterns of genetic variation diverge,” Stanford researcher Noah Rosenberg concludes.

The new study was supported by the US National Institutes of Health (NIH), the Burroughs Wellcome Fund and the William F. Milton Fund.