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Ancestral humans had more DNA

Atlas mapping genetic deletions and duplications reveals evolutionary relationships

2:21pm, August 6, 2015
Map of human genetic diversity

DNA DIVERSITY  A global atlas of human genetic diversity reveals that some Oceanians (purple) carry duplicated DNA inherited from Denisovans (black). No Neandertals nor any other human group carry the duplication (indicated by open circles). The black “Archaic” circle represents a Denisovan and a Neandertal.

A new atlas of human genetic diversity reveals what human ancestors’ DNA may have looked like before people migrated out of Africa.

Ancestral humans carried 40.7 million more DNA base pairs than people do today, researchers report online August 6 in Science. That’s enough DNA to build a small chromosome, says study coauthor Evan Eichler, an evolutionary geneticist at the University of Washington in Seattle.

Human ancestors in Africa jettisoned 15.8 million of those DNA base pairs — information-carrying building blocks of DNA often referred to by the letters A, T, G and C — before dispersing around the globe, the researchers discovered. As people left Africa and spread to other continents, they dropped more chunks of DNA. Eichler and colleagues have followed these genetic bread crumbs to map relationships among 125 human groups worldwide.

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