Featured Research

from universities, journals, and other organizations

Evolution's past is modern human's present: DNA evidence of ancient interbreeding inside Africa

Date:
September 7, 2011
Source:
National Science Foundation
Summary:
That seems to be the takeaway from new research that concludes "archaic" humans, somewhere in Africa during the last 20-60 thousand years, interbred with anatomically modern humans and transferred small amounts of genetic material to their offspring who are alive today. University of Arizona geneticist Michael Hammer and a team of evolutionary biologists, geneticists and mathematicians report the finding in today's Proceedings of the National Academy of Sciences.

The past is present when it comes to human evolution. That seems to be the takeaway from new research that concludes "archaic" humans, somewhere in Africa during the last 20-60 thousand years, interbred with anatomically modern humans and transferred small amounts of genetic material to their offspring who are alive today.

University of Arizona geneticist Michael Hammer and a team of evolutionary biologists, geneticists and mathematicians report the finding in the Proceedings of the National Academy of Sciences.

The National Science Foundation (NSF) in Arlington, Va., funded the study.

"It appears some level of interbreeding may have occurred in many parts of the world at different times in human evolution," said Hammer, whose work is the first to definitively suggest interbreeding between separate human forms inside of Africa.

Previous studies primarily examined modern human interbreeding with Neanderthals in Europe or other archaic forms in Asia. Analyses of ancient DNA in those studies suggest a small amount of gene flow occurred from Neanderthals into non-African offspring sometime after anatomically modern humans left Africa.

Additionally, researchers discovered evidence that a distinct group of extinct archaic humans who lived in Southern Siberia, called 'Denisovans,' contributed genetic material to the genomes of present-day Melanesians.

As Hammer and colleagues write in their recent report, "Given recent fossil evidence, however, the greatest opportunity for introgression was in Africa" where anatomically modern humans and various archaic forms co-existed for much longer than they did outside of Africa.

"We estimate that the archaic DNA fragments that survive in modern African genomes come from a form or forms that diverged from the common ancestor of anatomically modern humans 700 thousand to 1 million years ago," said Hammer.

"This archaic genetic material is more prevalent in west-central African populations, possibly reflecting a hybridization event or process that took place in central Africa," he said. "The populations that interbred were similar enough biologically so that they were able to produce fertile offspring, thus allowing genes to flow from one population to the other."

Hammer and team studied DNA sequence data from three sub-Saharan African populations: Mandenka, Biaka and San to test models of African archaic admixture.

The Mandenka are an agricultural population from West Africa, while the Biaka and the San are historically isolated hunter-gatherer populations from Central and Southern Africa, respectively.

The team conducted extensive simulations to test the likelihood of gene flow from an archaic population to anatomically modern humans. The simulations rejected the default position, or null hypothesis, that no admixture took place.

The result gave the scientists confidence to infer that contemporary African populations contain a small proportion of genetic material--about 2 percent--that moved from a species of archaic humans into the gene pool of anatomically modern humans about 35 thousand years ago.

They surmise that this archaic population split from the ancestors of anatomically modern humans about 700 thousand years ago.

"We do not have ancient DNA, i.e., from a fossil specimen, to directly compare with DNA from contemporary populations, so our approach was indirect or inferential," said Hammer. But there are several candidates in the African fossil record that may have added their genetic material to modern humans such as Homo heidelbergensis, an extinct species of the genus Homo that lived between 600 and 400 thousand years ago.

"This study represents an approach to answering long-standing questions about the contributions of archaic, extinct forms of our genus to the gene pool of our modern human species," said Carolyn Ehardt, Program Director for Biological Anthropology at NSF. "Previous to the advent of contemporary genetic techniques and approaches, the addressing of such pivotal questions in bioanthropological science was prohibitive."

Additionally, the research could provide greater insight into human physiology and assist the understanding of human diseases.

"It is entirely possible that some of the genes that were picked up from archaic forms by the ancestors of modern Africans were beneficial and are now part of the functional physiological machinery of contemporary populations," said Hammer. "This could be in the form of disease resistance alleles or other gene variations that led to novel adaptations in the modern population."

The research was funded by an NSF HOMINID grant that seeks to improve understanding of human origins.


Story Source:

The above story is based on materials provided by National Science Foundation. Note: Materials may be edited for content and length.


Journal Reference:

  1. M. F. Hammer, A. E. Woerner, F. L. Mendez, J. C. Watkins, J. D. Wall. Genetic evidence for archaic admixture in Africa. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1109300108

Cite This Page:

National Science Foundation. "Evolution's past is modern human's present: DNA evidence of ancient interbreeding inside Africa." ScienceDaily. ScienceDaily, 7 September 2011. <www.sciencedaily.com/releases/2011/09/110907171533.htm>.
National Science Foundation. (2011, September 7). Evolution's past is modern human's present: DNA evidence of ancient interbreeding inside Africa. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2011/09/110907171533.htm
National Science Foundation. "Evolution's past is modern human's present: DNA evidence of ancient interbreeding inside Africa." ScienceDaily. www.sciencedaily.com/releases/2011/09/110907171533.htm (accessed October 1, 2014).

Share This



More Fossils & Ruins News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

2,000 Year Old Pre-Inca Cloak on Display in Lima

2,000 Year Old Pre-Inca Cloak on Display in Lima

AFP (Sep. 27, 2014) A 2,000 year-old Pre-Inca cloak that is believed to represent an agricultural calendar of the Paracas culture is on display in Lima. Duration: 00:39 Video provided by AFP
Powered by NewsLook.com
Original Mozart Sonata Manuscript Found in Budapest

Original Mozart Sonata Manuscript Found in Budapest

AFP (Sep. 26, 2014) Considered lost for over two centuries, the original manuscript of one of the most famous works of Mozart's Sonata in A major has been uncovered in a library in Budapest. Duration: 01:04 Video provided by AFP
Powered by NewsLook.com
Underground Art Reveals WW1 Soldiers' Hopes and Fears

Underground Art Reveals WW1 Soldiers' Hopes and Fears

AFP (Sep. 25, 2014) American doctor and photographer Jeff Gusky reveals the underground quarries used by the soldiers of World War One, and the artwork they left behind which illustrates their hopes and fears. Duration: 02:15 Video provided by AFP
Powered by NewsLook.com
Raw: Ice Age Wooly Mammoth Remains for Sale

Raw: Ice Age Wooly Mammoth Remains for Sale

AP (Sep. 23, 2014) A rare, well-preserved skeleton of a woolly mammoth is going on sale at Summers Place Auctions hope the 11.5-foot tall, almost intact specimen will fetch between $245,000 to $409,000. (Sept. 23) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

More Coverage


Ancient Humans Were Mixing It Up: Anatomically Modern Humans Interbred With More Archaic Hominin Forms While in Africa

Sep. 5, 2011 Anatomically modern humans interbred with more archaic hominin forms even before they migrated out of Africa, a team of researchers has found. The discovery suggests genetic exchange with their more ... read more

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins