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Amerijoe
06-21-2016, 10:53 AM
Researchers from the University of Oxford have revealed that the genetic ancestries of many of sub-Saharan Africa's populations are the result of historical DNA mixing events, known as admixture, within the last 4000 years.

Their study, to be published in the journal eLife, uncovers signatures of these admixture events through a large analysis of DNA from populations across the continent. The discovery provides a foundation for the recent genetic history of the continent, which could aid future studies of non-communicable and infectious diseases, such as malaria.

While admixture has been demonstrated in other regions of the world, the new analysis has allowed the team to characterise sub-Saharan Africa's mixing events in an unprecedented level of detail.

'As Africa has few written records of its history, it is somewhat unknown what important movements of people generated the populations in the continent today,' says lead author George Busby, Statistical Geneticist at the Wellcome Trust Centre for Human Genetics.

'Looking at and comparing the differences in the genomes of people alive today can help us better understand and reconstruct the historical interactions that brought their ancestors together.'

The team used DNA analysis to characterise the structure of genetic diversity and gene flow the transfer of genes between different populations in a collection of 48 sub-Saharan African groups. The data used for these analyses were drawn from several sources, including a subset of samples collected for a malaria susceptibility study, MalariaGEN Consortial Project 1.

By applying recently published approaches designed to identify blocks of similar DNA within and between populations, they discovered that most sub-Saharan populations share ancestry with groups from outside their current geographic region as a result of gene flow within the last 4000 years. The approaches used by the team were particularly tuned to picking up signals of admixture from within this timescale.

'Our research provides further genetic evidence that the spread of Bantu languages and agricultural technology from Central West Africa, known as the Bantu expansion, was likely to be accompanied by people who moved from Cameroon to the south and east within the last 2500 years. Additionally, we revealed that coastal populations in western, eastern, and southern Africa experienced small influxes of Eurasian genes as a result of different events over the last 3000 years,' Dr Busby explains.

'These findings show that groups from similar parts of Africa experienced admixture events at similar times and involving similar sources, suggesting that genetic variation in these areas of the continent has been shaped by shared historical events. It is also clear that our ancestors have always moved about and traces of these migrations are left in the DNA of people alive today.'

Dr Busby adds that this research will be relevant to future epidemiology studies, which aim to uncover novel relationships between genes, the environment, and disease.

'An important next step will be to look at the consequences of our observed gene flow and ask if it has contributed to spreading beneficial or detrimental mutations around the continent,' he says.

Professor Dominic Kwiatkowski, from the Wellcome Trust Sanger Institute and the Wellcome Trust Centre for Human Genetics, adds: 'Africa has an exciting and important role to play in furthering our understanding of human biology and disease.

'Ongoing efforts to generate and analyse large-scale genomic data are yielding new insights into patterns of genetic diversity on the continent. This sheds light not only on the historical movements of its people, but also has the potential to transform how we make sense of genetic differences that effect the development and progression of various diseases, including malaria.'

Explore further: Can DNA evidence fill gaps in our history books?

More information: Admixture into and within sub-Saharan Africa, eLife, dx.doi.org/10.7554/eLife.15266
Journal reference: eLife
Provided by: University of Oxford

Piquerobi
06-21-2016, 11:32 AM
February 1, 2016
Abstract
Understanding patterns of genetic diversity is a crucial component of medical research in Africa.
Here we use haplotype-based population genetics inference to describe gene-flow and admixture in a
collection of 48 African groups with a focus on the major populations of the sub-Sahara. Our analysis
presents a framework for interpreting haplotype diversity within and between population groups and
provides a demographic foundation for genetic epidemiology in Africa. We show that coastal African
populations have experienced an influx of Eurasian haplotypes as a series of admixture events over
the last 7,000 years, and that Niger-Congo speaking groups from East and Southern Africa share
ancestry with Central West Africans as a result of recent population expansions associated with
the adoption of new agricultural technologies. We demonstrate that most sub-Saharan populations
share ancestry with groups from outside of their current geographic region as a result of large-scale
population movements over the last 4,000 years. Our in-depth analysis of admixture provides an
insight into haplotype sharing across different geographic groups and the recent movement of alleles
into new climatic and pathogenic environments, both of which will aid the interpretation of genetic
studies of disease in sub-Saharan Africa.
http://biorxiv.org/content/biorxiv/early/2016/02/01/038406.full.pdf

drobbah
06-21-2016, 05:48 PM
Interesting study but I think they are very off in terms of the dates of Eurasian admixture in Horners.For example they claim Somalis admixture happened right before O BCE which doesn't make sense!