Dating encounters between modern humans and Neandertals

To discover why Neandertals are most closely related to people outside Africa scientists have estimated the date when Neandertals and modern Europeans last shared ancestors

2012-10-05

(Press-News.org) To discover why Neandertals are most closely related to people outside Africa, Harvard and Max Planck Institute scientists have estimated the date when Neandertals and modern Europeans last shared ancestors. The research, published in the journal PLOS Genetics, provides a historical context for the interbreeding. It suggests that it occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa.

When the Neandertal genome was sequenced in 2010 it revealed that people outside Africa share slightly more genetic variants with Neandertals than Africans do. One scenario that could explain this observation is that modern humans mixed with Neandertals when they came out of Africa. An alternative, but more complex, scenario is that African populations ancestral to both Neandertals and modern humans remained subdivided over a few hundred thousand years and that those more related to Neandertals subsequently left Africa.

Dr. Sriram Sankararaman and colleagues measured the length of DNA pieces in the genomes of Europeans that are similar to Neandertals. Since recombination between chromosomes when egg and sperm cells are formed reduces the size of such pieces in each generation, the Neandertal-related pieces will be smaller the longer they have spent in the genomes of present-day people.

The team estimate that Neandertals and modern humans last exchanged genes between 37,000 and 86,000 years ago, well after modern humans appeared outside Africa but potentially before they started spreading across Eurasia. This suggests that Neandertals (or their close relatives) had children with the direct ancestors of present-day people outside Africa.

### FINANCIAL DISCLOSURE: This work was supported by the Presidential Innovation Fund of the Max Planck Society, the Krekeler Foundation, and the National Science Foundation (HOMINID grant 1032255). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

COMPETING INTERESTS: The authors have declared that no competing interests exist.

CITATION: Sankararaman S, Patterson N, Li H, Pääbo S, Reich D (2012) The Date of Interbreeding between Neandertals and Modern Humans. PLoS Genet 8(10):e1002947. doi:10.1371/journal.pgen.1002947 PLEASE ADD THIS LINK TO THE FREELY AVAILABLE ARTICLE IN ONLINE VERSIONS OF YOUR REPORT (the link will go live when the embargo ends): http://www.plosgenetics.org/doi/pgen.10029347

CONTACT: Dr. Sriram Sankararaman
Harvard Medical School
Dept of Genetics
77, Avenue Louis Pasteur
NRB 260
Boston, MA 02115
UNITED STATES
sankararaman@genetics.med.harvard.edu Disclaimer This press release refers to an upcoming article in PLOS Genetics. The release is provided by journal staff, or by the article authors and/or their institutions. Any opinions expressed in this release or article are the personal views of the journal staff and/or article contributors, and do not necessarily represent the views or policies of PLOS. PLOS expressly disclaims any and all warranties and liability in connection with the information found in the releases and articles and your use of such information. About PLOS Genetics PLOS Genetics reflects the full breadth and interdisciplinary nature of genetics and genomics research by publishing outstanding original contributions in all areas of biology. All works published in PLOS Genetics are open access. Everything is immediately and freely available online throughout the world subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License. About the Public Library of Science The Public Library of Science (PLOS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org.

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