Populations Intermixed Well After Migration out of Africa 60,000 Years

Populations Intermixed Well After Migration out of Africa 60,000 Years Ago 3 Efficient Process Using microRNA Converts Human Skin Cells Into Neurons 5 Last Dinosaur Before Mass Extinction Discovered 8 Ancient Algae: Genetically Engineering a Path to New Energy Sources? 10 Biologists Identify New Strategy Used by Bacteria During Infection 12 Researchers Identify Mechanism That Seems to Protect Brain from Aging 14 Bold New Approach to Wind 'Farm' Design May Provide Efficiency Gains 16 Computer Learns Language by Playing Games 18 Gray Whales Likely Survived the Ice Ages by Changing Their Diets 20 How the Battle Was Won, if Not Yet the War 24 Pterosaurs Not Driven Into Extinction by Birds, Study Reveals 30 Why My Father Hated India 32 Beauty Is in the Medial Orbito-Frontal Cortex of the Beholder 36 Mechanical Micro-Drum Cooled to Quantum Ground State 38 Rhesus Monkeys Have a Form of Self-Awareness Not Previously Attributed to Them 40 Cassini Captures Images and Sounds of Saturn Storm 42 New Force Driving Earth's Tectonic Plates 44 Cruelty in Fact and Fiction 46 Hydrogen Peroxide Found in Space 49 Research and Politics 52 How Hot Did Earth Get in the Past? 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(Credit: © Sailorr / Fotolia) ScienceDaily (July 13, 2011) — Researchers have probed deeper into human evolution by developing an elegant new technique to analyse whole genomes from different populations. One key finding from the Wellcome Trust Sanger Institute's study is that African and non-African populations continued to exchange genetic material well after migration out-of-Africa 60,000 years ago. This shows that interbreeding between these groups continued long after the original exodus. For the first time genomic archaeologists are able to infer population size and history using single genomes, a technique that makes fewer assumptions than existing methods, allowing for more detailed insights. It provides a fresh view of the history of humankind from 10,000 to one million years ago. "Using this algorithm, we were able to provide new insights into our human history," says Dr Richard Durbin, joint head of Human Genetics and leader of the Genome Informatics Group at the Sanger Institute. "First, we see an apparent increase in effective human population numbers around the time that modern humans arose in Africa over 100,000 years ago. "Second, when we look at non-African individuals from Europe and East Asia, we see a shared history of a dramatic reduction in population, or bottleneck, starting about 60,000 years ago, as others have also observed. But unlike previous studies we also see evidence for continuing genetic exchange with African populations for tens of thousands of years after the initial out-of-Africa bottleneck until 20,000 to 40,000 years ago. "Previous methods to explore these questions using genetic data have looked at a subset of the human genome. Our new approach uses the whole sequence of single individuals, and relies on fewer assumptions. Using such techniques we will be able to capitalize on the revolution in genome sequencing and analysis from projects such as The 1000 Genomes Project, and, as more people are sequenced, build a progressively finer detail picture of human genetic history." 3 Infoteca’s E-Journal No. 166 August 2011 Sistema de Infotecas Centrales Universidad Autónoma de Coahuila The team sequenced and compared four male genomes: one each from China, Europe, Korea and West Africa respectively. The researchers found that, although the African and non-African populations might have started to differentiate as early as 100,000 to 120,000 years ago, they largely remained as one population until approximately 60,000 to 80,000 years ago. Following this the European and East Asian ancestors went through a period where their effective population size crashed to approximately one-tenth of its earlier size, overlapping the period when modern human fossils and artefacts start to appear across Europe and Asia. But, for at least the first 20,000 years of this period, it appears that the out-of-Africa and African populations were not genetically separated. A possible explanation could be that new emigrants from Africa continued to join the out-of-Africa populations long after the original exodus. "This elegant tool provides opportunities for further research to enable us to learn more about population history," says co-author Heng Li, from the Sanger Institute. "Each human genome contains information from the mother and the father, and the differences between these at any place in the genome carry information about its history. Since the genome sequence is so large, we can combine the information from tens of thousands of different places in the genome to build up a composite history of the ancestral contributions to the particular individual who was sequenced. "We can also get at the historical relationship between two different ancestral populations by comparing the X chromosomes from two males. This works because men only have one copy of the X chromosome each, so we can combine the X chromosomes of two men and treat them in the same way as the rest of the genome for one person, with the results telling us about the way in which the ancestral populations of the two men separated. "The novel statistical method we developed is computationally efficient and doesn't make restrictive assumptions about the way that population size changed. Although not inconsistent with previous results, these findings allow new types of historical events to be explored, leading to new observations about the history of mankind." The researchers believe that this technique can be developed further to enable even more fine-grained discoveries by sequencing multiple genomes from different populations. In addition, beyond human history, there is also the potential to investigate the population size history of other species for which a single genome sequence has been obtained. Story Source: The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Wellcome Trust Sanger Institute, via EurekAlert!, a service of AAAS. Journal Reference: 1. Heng Li, Richard Durbin. Inference of human population history from individual whole-genome sequences.

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