Writing history with DNA

Credit: Busby et al./Current Biology 2015

Gene flow within West Eurasia is shown by lines linking the best-matching 
donor group to the sources of admixture with recipient clusters (arrowhead). 
Line colors represent the regional identity of the donor group, and line thick-
ness represents the proportion of DNA coming from the donor group. Ranges
of the dates (point estimates) for events involving sources most similar to 
selected donor groups are shown.
It's often said that the history we know was written by the winners with the losers lost to history and memory.

Until the age of DNA analysis, that is.

DNA retains a record of historic events, and the collective DNA of a population can be used to trace historic movements of entire populations or invasions by outside groups. Using DNA allows us to trace historic movements of peoples in pre-history, such as recent research that shows that an unknown somewhat mysterious population invented agriculture, or that agriculture spread in a leap-frogging movement along coasts, or that some tribes in Scandinavia actively resisted the expansion of agriculture into their lands.

As the map above shows, DNA analysis shows how various populations moved around Europe during pre-history, tracking winners and losers alike.

I'm intrigued by the idea of being able to analyse a person's or a family's history as shown by their DNA, tracking back thousands if not hundreds of thousands of years, creating a family tree of sorts with very deep roots.

Here's the report, with a link to the original study paper in the attribution.
*  *  *  *  *

Can DNA evidence fill gaps in our history books?

If you go back far enough, all people share a common ancestry. But some populations are more closely related than others based on events in the past that brought them together. Now, researchers have shown that it's possible to use DNA evidence as a means to reconstruct and date those significant past events. The findings suggest that evidence in our genomes can help to recover lost bits of history.

Mapping Human History:
Genes, Race, and
Our Common Origins

by Steve Olson

Order new and used from
Powell's Books
"We now have the statistical machinery to uncover which historical events have produced the mosaic genomes of people in Europe today," says George Busby of the University of Oxford. "The successful reconstruction of the genetic history of a region of the world that has been well investigated both archaeologically and historically suggests that these approaches have the potential to be applied to areas where history has not been so well recorded and where genetics might be the only way of recovering history."

Busby and his colleagues applied a new method they've developed to compare single genetic variants among populations, taking into account the relationships among those markers based on their physical proximity along the chromosomes. That information can be used to infer subtle relationships among populations, including those that are genetically very similar, as well as the history of a continent.

The new work shows that all European populations have mixed over time as people picked up and moved from one place to another. Usually this mixing has involved nearby groups, but sometimes populations bear the mark of invading populations from more distant locations.

"Much as different cultures have often borrowed elements from each other, we are now seeing that the genomes of people alive in Europe today contain ancestry from multiple different places, from within Europe and outside," says Cristian Capelli, the study's senior author.

The results offer interesting insights into human history, including the lives of "regular people."

"History is often written by the winners and the elites--we often do not hear about the everyday life of people," Busby says. "By studying the DNA of populations and understanding how different groups are ancestrally related to each other, our analysis tells the story of all people."

For example, the researchers found evidence of contact across Central Asia with groups from Mongolia. In fact, they see evidence that Mongolians migrated into Europe in two waves: once at a time that matches the known expansions of Genghis Khan and the other occurring much earlier, prior to 1000 CE in groups of North East Europe, including the Chuvash, Russians, and Mordovians.

The researchers also see evidence of mixing among Europeans in the Mediterranean and people from West and North Africa at many times and places over the course of history. The Slavic expansion also left its mark on European genomes, showing that this was a key event in the genetic history of the region.

The researchers say it's now "clear that migration and admixture have been the norm, rather than the exception, throughout human history."

Related stories:
Story Source:  Materials provided by Cell Press.  Busby et al. The Role of Recent Admixture in Forming the Contemporary West Eurasian Genomic Landscape. Current Biology, September 2015


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