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	Podcast:		UC Science Today
	Episode:		How scientists date when populations diverged from a common ancestor
	Category:		Science & Medicine
	Duration:		00:01:02
	Publish Date:		2015-10-12 19:00:00
	Description:		Have you ever wondered how scientists date evolutionary events such as when two populations diverged from a common ancestor? Computational biologist Rasmus Nielsen of the University of California, Berkeley says that one method is to use what’s called a molecular clock, which involves counting the mutations in DNA between ancient and living individuals. "If we take some DNA from you and some DNA from me that DNA will not be identical to each other. It will differ a little bit because there will be mutations that have accumulated in time since we had our most recent common ancestor. Since in the past thousands of years ago, there was some individual that is the ancestor of both of us. By counting mutations, we can figure out something about how long ago since we had our most recent common ancestor. By doing that we can then put dates on these different events, as for example, when did Native Americans start to split up from each other?" By counting mutations, Nielsen’s team estimated that the first Native Americans split into northern and southern populations around 13,000 years ago. "And that helped us quite a lot, to distinguish between different hypotheses about how the American continents were peopled."
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