Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Population genetics reveals shared ancestries

25.05.2011
More than just a tool for predicting health, modern genetics is upending long-held assumptions about who we are. A new study by Harvard researchers casts new light on the intermingling and migration of European, Middle Eastern and African and populations since ancient times.

In a paper titled "The History of African Gene Flow into Southern Europeans, Levantines and Jews," published in PLoS Genetics, HMS Associate Professor of Genetics David Reich and his colleagues investigated the proportion of sub-Saharan African ancestry present in various populations in West Eurasia, defined as the geographic area spanning modern Europe and the Middle East. While previous studies have established that such shared ancestry exists, they have not indicated to what degree or how far back the mixing of populations can be traced.

Analyzing publicly available genetic data from 40 populations comprising North Africans, Middle Easterners and Central Asians were doctoral student Priya Moorjani and Alkes Price, an assistant professor in the Program in Molecular and Genetic Epidemiology within the Department of Epidemiology at the Harvard School of Public Health.

Moorjani traced genetic ancestry using a method called rolloff. This platform, developed in the Reich lab, compares the size and composition of stretches of DNA between two human populations as a means of estimating when they mixed. The smaller and more broken up the DNA segments, the older the date of mixture.

Moorjani used the technique to examine the genomes of modern West Eurasian populations to find signatures of Sub-Saharan African ancestry. She did this by looking for chromosomal segments in West Eurasian DNA that closely matched those of Sub-Saharan Africans. By plotting the distribution of these segments and estimating their rate of genetic decay, Reich's lab was able to determine the proportion of African genetic ancestry still present, and to infer approximately when the West Eurasian and Sub-Saharan African populations mixed.

"The genetic decay happens very slowly," Moorjani explained, "so today, thousands of years later, there is enough evidence for us to estimate the date of population mixture."

While the researchers detected no African genetic signatures in Northern European populations, they found a distinct presence of African ancestry in Southern European, Middle Eastern and Jewish populations. Modern southern European groups can attribute about 1 to 3 percent of their genetic signature to African ancestry, with the intermingling of populations dating back 55 generations, on average—that is, to roughly 1,600 years ago. Middle Eastern groups have inherited about 4 to 15 percent, with the mixing of populations dating back roughly 32 generations. A diverse array of Jewish populations can date their Sub-Saharan African ancestry back roughly 72 generations, on average, accounting for 3 to 5 percent of their genetic makeup today.

According to Reich, these findings address a long-standing debate over African multicultural influences in Europe. The dates of population mixtures are consistent with documented historical events. For example, the mixing of African and southern European populations coincides with events during the Roman Empire and Arab migrations that followed. The older-mixture dates among African and Jewish populations are consistent with events in biblical times, such as the Jewish diaspora that occurred in 8th to 6th century BC.

"Our study doesn't prove that the African ancestry is associated with migrations associated with events in the Bible documented by archeologists," Reich says, "but it's interesting to speculate."

Reich was surprised to see any level of shared ancestry between the Ashkenazi and non-Ashkenazi Jewish groups. "I've never been convinced they were actually related to each other," Reich says, but he now concludes that his lab's findings have significant cultural and genetic implications. "Population boundaries that many people think are impermeable are, in fact, not that way."

David Cameron | EurekAlert!
Further information:
http://www.hms.harvard.edu

More articles from Life Sciences:

nachricht The irresistible fragrance of dying vinegar flies
16.08.2017 | Max-Planck-Institut für chemische Ökologie

nachricht How protein islands form
15.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

Im Focus: Scientists improve forecast of increasing hazard on Ecuadorian volcano

Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).

The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New thruster design increases efficiency for future spaceflight

16.08.2017 | Physics and Astronomy

Transporting spin: A graphene and boron nitride heterostructure creates large spin signals

16.08.2017 | Materials Sciences

A new method for the 3-D printing of living tissues

16.08.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>