In an intriguing original look at the history of the first Americans, a study finds evidence that the north-south orientation of the continents slowed the spread of populations and technology, compared to the east-west axis of Eurasia. The research by Sohini Ra-machandran and Noah Rosenberg, from Brown University, Providence, R.I., and Stanford (Calif.) University, respectively, uses genetic information to explore the effects of continental axes and climates on human migration and adaptation across the Americas.
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