Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Evolution's past is modern human's present

Mandenka, Biaka and San tested for DNA evidence of ancient interbreeding inside Africa

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 today's 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.

Bobbie Mixon | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Gene therapy shows promise for treating Niemann-Pick disease type C1
27.10.2016 | NIH/National Human Genome Research Institute

nachricht 'Neighbor maps' reveal the genome's 3-D shape
27.10.2016 | International School of Advanced Studies (SISSA)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

How nanoscience will improve our health and lives in the coming years

27.10.2016 | Materials Sciences

OU-led team discovers rare, newborn tri-star system using ALMA

27.10.2016 | Physics and Astronomy

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

More VideoLinks >>>