Mixture and migration brought food production to sub-Saharan Africa
Ancient DNA documents the population changes of foragers, herders and
farmers in central and eastern Africa from the Neolithic to the Iron Age

Date:
June 12, 2020
Source:
Max Planck Institute for the Science of Human History
Summary:
A new interdisciplinary study reports on 20 newly sequenced ancient
genomes from sub-Saharan Africa, including the first genomes from
the Democratic Republic of the Congo, Botswana, and Uganda. The
study documents the coexistence, movements, interactions and
admixture of diverse human groups during the spread of food
production in sub-Saharan Africa.



FULL STORY ==========================================================================
In order to reveal the population interactions that gave rise to
Africa's enormous linguistic, cultural, and economic diversity, an interdisciplinary team of researchers from Africa, Europe, and North
America sampled key regions in which current models predict a legacy
of significant population interactions. The collaborative study between researchers at the Max Planck Institute for the Science of Human History (MPI-SHH), the National Museums of Kenya and other partners was led
by archaeogeneticist Ke Wang and archaeologist Steven Goldstein of
MPI-SHH. It sheds light on patterns of population change as food
production spread throughout sub-Saharan Africa.


==========================================================================
A Complex Mosaic of Interactions While the spread of food production led
to the gradual replacement of local foragers in most parts of the world, foraging lifeways have persisted in several regions of contemporary
Africa among populations such as the San in the south, the Hazda in the
east and the Mbuti of the central African rainforest.

However, the present study shows that, thousands of years ago, the
ancestors of these groups once formed an overlapping genetic cline that stretched across much of eastern and southern Africa.

"Restricted gene flow between regional forager groups in contemporary
eastern, southern, and central Africa, whether due to climactic and environmental factors or as a result of encapsulation by food producing
groups, has likely contributed substantially to the spatial genetic
structure we can see across the continent today," says Ke Wang.

"We are still at a point where we learn a lot from every individual,"
Steven Goldstein adds, "the interactions between hunter-gatherers, pastoralists, and farmers were more complex even into recent centuries
than we previously understood." To better understand these interactions
and their impact on subsistence strategies, the researchers focused
their investigations on key groups and regions previously identified
as significant contributors to changes in food production: eastern and
southern forager groups, eastern African Pastoral Neolithic and Iron
Age groups, and Iron Age groups related to present-day Bantu speakers.



========================================================================== Mixture and migration during the Pastoral Neolithic Genomic analysis
of the six individuals here reported from Kenya's Pastoral Neolithic
period (between 4,500 and 1,200 years ago) revealed greater ancestral complexity than previously reported individuals from the same region, supporting previous studies that have proposed early herders migrated
south along multiple simultaneous but geographically distinct routes.

"In such a scenario," Dr. Emmanuel Ndiema of the National Museums of
Kenya explains, "a single base population in northern Africa may have
branched into many as some herding groups moved along the Nile corridor,
some through southern Ethiopia, and possibly some through eastern Uganda." Along the way, migrating pastoralists would have encountered different populations and formed varying inter-community relationships, ultimately resulting in varying integration of diverse ancestries. This model may
explain why archaeologists observe stark differences in material culture, settlement strategies and burial traditions between Pastoral Neolithic populations whose ancestries are in fact closely related.

The Iron Age and the Bantu Expansion Some of the most exciting findings
come from the site of Kakapel Rockshelter in western Kenya, where the
National Museums of Kenya and the MPI-SHH have teamed up to investigate
early farming in the region.



==========================================================================
At Kakapel, two individuals dated to roughly 300 and 900 years ago
show significant increases in ancestry related to people speaking
Nilotic languages today, such as the Dinka from South Sudan, compared to previously published genomes from the Central Rift Valley. This suggests
that genetic turnover must have been region-specific and could have
involved multiple divergent migrations. Genomic analysis revealed that
the 900-year-old individual had close affinity with Dinka populations,
but also showed influence from West- Eurasian or North-African groups, suggesting that the population that this individual represents formed
between Pastoral Neolithic-related herders and incoming Nilotic (Nile
Valley) agropastoralists -- not from a major migration of groups with
western African ancestries.

Similar evidence is detected from Botswana, where analysis detected the
first archaeogenetic support for the hypotheses that herders from eastern Africa spread to southern Africa before the arrival of Bantu-speaking
farmers. Despite raising questions about the uniformity of the Bantu
Expansion, the current study documents the arrival of people with
Bantu-related ancestry in Botswana during the first millennium CE and
their subsequent admixture with eastern African pastoralist and southern African forager populations.

"We identified Bantu-related ancestry in Uganda, western Congo,
Tanzania and Kenya, which is consistent with the well-documented genetic homogenization caused by the Bantu expansion," says Stephan Schiffels of
the MPI-SHH, "but we also see highly variable patterns of Bantu admixture
with regional forager and pastoralist populations in southern Africa."
"While supraregional studies can help reveal population interactions on a continental scale," says Schiffels, "we want to emphasize the importance
of regionally focused studies to better understand local patterns of
cultural and population changes in the future."

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_the_Science_of_Human_History.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ke Wang et al. Ancient genomes reveal complex patterns of population
movement, interaction, and replacement in sub-Saharan
Africa. Science Advances, 2020 DOI: 10.1126/sciadv.aaz0183 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200612172240.htm

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