Innovation by ancient farmers adds to biodiversity of the Amazon

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IMAGE: INNOVATION BY ANCIENT FARMERS TO IMPROVE SOIL FERTILITY CONTINUES TO HAVE AN IMPACT ON THE BIODIVERSITY OF THE AMAZON, A MAJOR NEW STUDY SHOWS. view more 

CREDIT: BEN HUR MARIMON JUNIOR

Innovation by ancient farmers to improve soil fertility continues to have an impact on the biodiversity of the Amazon, a major new study shows.

Early inhabitants fertilized the soil with charcoal from fire remains and food waste. Areas with this "dark earth" have a different set of species than the surrounding landscape, contributing to a more diverse ecosystem with a richer collection of plant species, researchers from the State University of Mato Grosso in Brazil and the University of Exeter have found.

The legacy of this land management thousands of years ago means there are thousands of these patches of dark earth dotted around the region, most around the size of a small field. This is the first study to measure the difference in vegetation in dark and non-dark earth areas in mature forests across a region spanning a thousand kilometers.

The team of ecologists and archaeologists studied abandoned areas along the main stem of the Amazon River near Tapajós and in the headwaters of the Xingu River Basin in southern Amazonia.

Lead author Dr Edmar Almeida de Oliveira said: "This is an area where dark earth lush forests grow, with colossal trees of different species from the surrounding forest, with more edible fruit trees, such as taperebá and jatobá."

The number of indigenous communities living in the Amazon collapsed following European colonization of the region, meaning many dark earth areas were abandoned.

The study, published in the journal Global Ecology and Biogeography, reveals for the first time the extent to which pre-Columbian Amerindians influenced the current structure and diversity of the Amazon forest of the areas they once farmed.

Researchers sampled around 4,000 trees in southern and eastern Amazonia. Areas with dark earth had a significantly higher pH and more nutrients that improved soil fertility. Pottery shards and other artefacts were also found in the rich dark soils.

Professor Ben Hur Marimon Junior, from the State University of Mato Grosso, said: "Pre-Columbian indigenous people, who fertilized the poor soils of the Amazon for at least 5,000 years, have left an impressive legacy, creating the dark earth, or Terras Pretas de Índio"

Professor José Iriarte, an archaeologist from the University of Exeter, said: "By creating dark earth early inhabitants of the Amazon were able to successfully cultivate the soil for thousands of years in an agroforestry system

"We think ancient communities used dark earth areas to grow crops to eat, and adjacent forests without dark earth for agroforestry."

Dr Ted Feldpausch, from the University of Exeter, who co-authored the study with Dr Luiz Aragão from the National Institute for Space Research (INPE) in Brazil, said: "After being abandoned for hundreds of years, we still find a fingerprint of the ancient land-use in the forests today as a legacy of the pre-Colombian Amazonian population estimated in millions of inhabitants.

"We are currently expanding this research across the whole Amazon Basin under a project funded by the UK Natural Environment Research Council (NERC) to evaluate whether historical fire also affected the forest areas distant from the anthropogenic dark earths".

Many areas with dark earth are currently cultivated by local and indigenous populations, who have had great success with their food crops. But most are still hidden in the native forest, contributing to increased tree size, carbon stock and regional biodiversity. For this reason, the lush forests of the "Terra Preta de Índio" and their biological and cultural wealth in the Amazon must be preserved as a legacy for future generations, the researchers have said. Areas with dark earth are under threat due to illegal deforestation and fire.

"Dark earth increases the richness of species, an important consideration for regional biodiversity conservation. These findings highlight the small?scale long?term legacy of pre?Columbian inhabitants on the soils and vegetation of Amazonia," said co-author Prof Beatriz Marimon, from the State University of Mato Grosso.

First-degree incest: ancient genomes uncover Irish passage tomb dynastic elite

TRINITY COLLEGE DUBLIN

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IMAGE: NEWGRANGE AS SEEN ON A MISTY MORNING. view more 

CREDIT: KEN WILLIAMS, SHADOWSANDSTONE.COM

> The genome of an adult male from the heart of the world famous Newgrange passage tomb points to first-degree incest, implying dynasty and echoing local place-name folklore first recorded in Medieval times
> Far-flung kinship ties between Newgrange and passage tomb cemeteries in the west (Carrowkeel and Carrowmore, Co. Sligo) indicate an elite social stratum was widespread
> Before megalith builders arrived en masse, Ireland was home to a small hunter-gatherer population, whose genomes speak of long-term isolation from Britain and Europe
> The earliest case of Down Syndrome was discovered in a male infant from the famous Poulnabrone portal tomb

Archaeologists and geneticists, led by those from Trinity College Dublin, have shed new light on the earliest periods of Ireland's human history.

Among their incredible findings is the discovery that the genome of an adult male buried in the heart of the Newgrange passage tomb points to first-degree incest, implying he was among a ruling social elite akin to the similarly inbred Inca god-kings and Egyptian pharaohs.

Older than the pyramids, Newgrange passage tomb in Ireland is world famous for its annual solar alignment where the winter solstice sunrise illuminates its sacred inner chamber in a golden blast of light. However, little is known about who was interred in the heart of this imposing 200,000 tonne monument or of the Neolithic society which built it over 5,000 years ago.

The survey of ancient Irish genomes, published today in leading international journal, Nature, suggests a man who had been buried in this chamber belonged to a dynastic elite. The research, led by the research team from Trinity, was carried out in collaboration with colleagues from University College London, National University of Ireland Galway, University College Cork, University of Cambridge, Queen's University Belfast, and Institute of Technology Sligo.

"I'd never seen anything like it," said Dr Lara Cassidy, Trinity, first author of the paper. "We all inherit two copies of the genome, one from our mother and one from our father; well, this individual's copies were extremely similar, a tell-tale sign of close inbreeding. In fact, our analyses allowed us to confirm that his parents were first-degree relatives."

Matings of this type (e.g. brother-sister unions) are a near universal taboo for entwined cultural and biological reasons. The only confirmed social acceptances of first-degree incest are found among the elites - typically within a deified royal family. By breaking the rules, the elite separates itself from the general population, intensifying hierarchy and legitimizing power. Public ritual and extravagant monumental architecture often co-occur with dynastic incest, to achieve the same ends.

"Here the auspicious location of the male skeletal remains is matched by the unprecedented nature of his ancient genome," said Professor of Population Genetics at Trinity, Dan Bradley. "The prestige of the burial makes this very likely a socially sanctioned union and speaks of a hierarchy so extreme that the only partners worthy of the elite were family members."

The team also unearthed a web of distant familial relations between this man and other individuals from sites of the passage tomb tradition across the country, including the mega-cemeteries of Carrowmore and Carrowkeel in Co. Sligo.

"It seems what we have here is a powerful extended kin-group, who had access to elite burial sites in many regions of the island for at least half a millennium," added Dr Cassidy.

Remarkably, a local myth resonates with these results and the Newgrange solar phenomenon. First recorded in the 11th century AD, four millennia after construction, the story tells of a builder-king who restarted the daily solar cycle by sleeping with his sister. The Middle Irish place name for the neighbouring Dowth passage tomb, Fertae Chuile, is based on this lore and can be translated as 'Hill of Sin'.

"Given the world-famous solstice alignments of Brú na Bóinne, the magical solar manipulations in this myth already had scholars questioning how long an oral tradition could survive," said Dr Ros Ó Maoldúin, an archaeologist on the study. "To now discover a potential prehistoric precedent for the incestuous aspect is extraordinary."

The genome survey stretched over two millennia and unearthed other unexpected results. Within the oldest known burial structure on the island, Poulnabrone portal tomb, the earliest yet diagnosed case of Down Syndrome was discovered in a male infant who was buried there five and a half thousand years ago. Isotope analyses of this infant showed a dietary signature of breastfeeding. In combination, this provides an indication that visible difference was not a barrier to prestige burial in the deep past.

Additionally, the analyses showed that the monument builders were early farmers who migrated to Ireland and replaced the hunter-gatherers who preceded them. However, this replacement was not absolute; a single western Irish individual was found to have an Irish hunter-gatherer in his recent family tree, pointing toward a swamping of the earlier population rather than an extermination.

Genomes from the rare remains of Irish hunter-gatherers themselves showed they were most closely related to the hunter-gatherer populations from Britain (e.g. Cheddar Man) and mainland Europe. However, unlike British samples, these earliest Irelanders had the genetic imprint of a prolonged island isolation. This fits with what we know about prehistoric sea levels after the Ice Age: Britain maintained a land bridge to the continent long after the retreat of the glaciers, while Ireland was separated by sea and its small early populations must have arrived in primitive boats.

A Neandertal from Chagyrskaya Cave

Neandertals may have lived in very small groups, and genes expressed in the basal ganglia of their brains may have changed

MAX PLANCK INSTITUTE FOR EVOLUTIONARY ANTHROPOLOGY

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IMAGE: RESEARCHERS HAVE SEQUENCED THE GENOME OF A NEANDERTAL FROM CHAGYRSKAYA CAVE IN THE ALTAI MOUNTAINS TO HIGH QUALITY.view more 

CREDIT: DR. BENCE VIOLA, DEPT. OF ANTHROPOLOGY, U. OF TORONTO

The researchers extracted the DNA from bone powder and sequenced it to high quality. They estimate that the female Neandertal lived 60,000-80,000 years ago. From the variation in the genome they estimate that she and other Siberian Neandertals lived in small groups of less than 60 individuals. The researchers also show that the Chagyrskaya Neandertal was more closely related to the Croatian than to the other Siberian Neandertal which lived some 40,000 years before the Chagyrskaya Neandertal. This shows that Neandertal populations from the West at some point replaced other Neandertal populations in Siberia.

"We also found that genes expressed in the striatum of the brain during adolescence showed more changes that altered the resulting amino acid when compared to other areas of the brain", says Fabrizio Mafessoni, lead author of the study. The results suggest that the striatum - a part of the brain which coordinates various aspects of cognition, including planning, decision-making, motivation and reward perception - may have played a unique role in Neandertals.

Seafood helped prehistoric people migrate out of Africa

Prehistoric pioneers could have relied on shellfish to sustain them as they followed migratory routes out of Africa during times of drought, a new study suggests.

The study examined fossil reefs near to the now-submerged Red Sea shorelines that marked prehistoric migratory routes from Africa to Arabia. The findings suggest this coast offered the resources necessary to act as a gateway out of Africa during periods of little rainfall when other food sources were scarce.

The research team, led by the University of York, focused on the remains of 15,000 shells dating back 5,000 years to an arid period in the region. With the coastline of original migratory routes submerged by sea-level rise after the last Ice Age, the shells came from the nearby Farasan Islands in Saudi Arabia.

The researchers found that populations of marine mollusks were plentiful enough to allow continuous harvests without any major ecological impacts and their plentiful availability would have enabled people to live through times of drought.

Lead author, Dr Niklas Hausmann, Associate Researcher at the Department of Archaeology at the University of York, said: "The availability of food resources plays an important role in understanding the feasibility of past human migrations -- hunter-gatherer migrations would have required local food sources and periods of aridity could therefore have restricted these movements.

"Our study suggests that Red Sea shorelines had the resources necessary to provide a passage for prehistoric people."

The study also confirms that communities settled on the shorelines of the Red Sea could have relied on shellfish as a sustainable food resource all year round.

Dr Hausmann added: "Our data shows that at a time when many other resources on land were scarce, people could rely on their locally available shellfish. Previous studies have shown that people of the southern Red Sea ate shellfish year-round and over periods of thousands of years. We now also know that this resource was not depleted by them, but shellfish continued to maintain a healthy population."

The shellfish species found in the archaeological sites on the Farasan Islands were also found in abundance in fossil reefs dating to over 100 thousand years ago, indicating that these shellfish have been an available resource over longer periods than archaeological sites previously suggested.

Co-author of the study, Matthew Meredith-Williams, from La Trobe University, said: "We know that modelling past climates to learn about food resources is extremely helpful, but we need to differentiate between what is happening on land and what is happening in the water. In our study we show that marine foods were abundant and resilient and being gathered by people when they couldn't rely on terrestrial food."

Immune properties in ancient DNA found in isolated villages might benefit humanity today

TGen-led international study traces genetic diversity among hunter-gathers of Indonesia, including last significant vestige of DNA from extinct human cousins

THE TRANSLATIONAL GENOMICS RESEARCH INSTITUTE

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PHOENIX, Ariz. -- June 15, 2020 -- Could remnants of DNA from a now extinct human subspecies known as the Denisovans help boost the immune functions of modern humans?

An international study co-led by the Translational Genomics Research Institute (TGen), an affiliate of City of Hope, and published in the scientific journal PLOS Genetics, represents the first characterizations of genes in the DNA of healthy individuals from geographically and genetically distinct populations in Indonesia.

Scientists studied genomic diversity among 116 individuals from three Indonesian populations: the Mentawai on the west coast of Sumatra; the Sumba in central Indonesia; and the Korowai, a group of hunter-gatherers from the western side of the isle of New Guinea.

The Korowai are of particular interest, as their DNA holds the world's last remaining significant remnants of genetic code -- as much as 5% -- from a cousin of modern humans called the Denisovans, the study says. Like the better-known Neanderthals of Europe, the Denisovans of Asia also are an extinct human subspecies who lived tens of thousands of years ago. And just as Neanderthals passed on certain immune properties to those of European ancestry, the Denisovans may have passed on protective immune genes to their southeast Asian decedents.

"Genome sequencing efforts have mainly focused on populations of European descent," said Dr. Heini Natri, a TGen postdoctoral fellow and one of the lead authors of the study. "Most of the world is deeply understudied. As we move further into the age of personalized and genomic medicine, understanding how genetics drives disease-risk across diverse populations is crucially important."

Why study Indonesia?

Spread across more than 17,000 islands between mainland Asia and Australia, Indonesia is the world's largest archipelago. Geographically as large as the U.S. or Europe, Indonesia's 273 million inhabitants make it the world's fourth most populous nation, after China, India and the U.S. And yet, Indonesia has been largely excluded from the genomics sequencing boom of the past decade, and there previously have been no analyses of diversity in gene regulation in either Indonesia or the other island nations of southeast Asia.

"This lack of information from Indonesia is alarming as it is an epicenter of infectious disease diversity, such as malaria and other emerging tropical diseases," Dr. Natri said. "Immune pressure from infectious diseases are responsible for some of the strongest selective forces on humans throughout our species' evolutionary history, and Indonesia offers unique advantages for studying responses to these diseases."

Because of Indonesia's island environment, its many isolated villages and the relatively low population density on most of its nearly 6,000 inhabited islands, the study suggests there is low genetic diversity among those who live on each island, and even in each village, but also high genetic diversity among people from island to island, "making it a near unique study system for examining gene-by-environment interactions," the study said.

Scientists focus on immune properties of ancient human DNA

Dr. Nicholas Banovich, an Assistant Professor in TGen's Integrated Cancer Genomics Division, a human geneticist, and a senior author of this PLOS Genetics paper, said the study's results highlight genes involved in the function of immune cells. This suggests a potentially adaptive response to local environmental pressures, including pressures from various tropical diseases.

"One of the unique aspects of Indonesia is individuals on the island of New Guinea have high remnants of DNA from one of our extinct ancestors, the Denisovans," Dr. Banovich said. "We found these remnants of ancient DNA are driving changes in genes involved in immune function. This study demonstrates the power of including understudied populations in an effort to increase the overall understanding of human genetics."

The international team is continuing its study, integrating more genetic data, exploring patterns of local ancestry and how archaic human genes are imbedded in modern-day populations.

"We are now attempting to pinpoint individual genetic changes -- in particular, those that are carried over in these remnant DNA fragments from Denisovans -- which regulate how much or how little a gene is turned on, and how these genetic changes may shape immune response," Dr. Natri said.

Discovery of oldest bow and arrow technology in Eurasia

IMAGE: FA-HIEN LENA HAS EMERGED AS ONE OF SOUTH ASIA'S MOST IMPORTANT ARCHAEOLOGICAL SITES SINCE THE 1980S, PRESERVING REMAINS OF OUR SPECIES, THEIR TOOLS, AND THEIR PREY IN A TROPICAL CONTEXT.... view more 

CREDIT: LANGLEY ET AL., 2020

The origins of human innovation have traditionally been sought in the grasslands and coasts of Africa or the temperate environments of Europe. More extreme environments, such as the tropical rainforests of Asia, have been largely overlooked, despite their deep history of human occupation. A new study provides the earliest evidence for bow-and-arrow use, and perhaps the making of clothes, outside of Africa ~48-45,000 years ago -in the tropics of Sri Lanka.

The island of Sri Lanka in the Indian Ocean, just south of the Indian subcontinent, is home to the earliest fossils of our species, Homo sapiens, in South Asia. It also preserves clear evidence for human occupation and the use of tropical rainforest environments outside of Africa from ~48,000 to 3,000 years ago - refuting the idea that these supposedly resource-poor environments acted as barriers for migrating Pleistocene humans. The question as to exactly how humans obtained rainforest resources - including fast-moving food sources like monkeys and squirrels - remains unresolved.

In this new study, published in Science Advances, an international team of researchers from the Max Planck Institute for the Science of Human History (MPI-SHH) in Germany, Griffith University in Australia and the Department of Archaeology, Government of Sri Lanka, present evidence for the earliest use of bow-and-arrow technologies by humans anywhere outside of Africa. At ~48,000 years old, these tools are earlier than the first similar technology found in Europe. Clear evidence for use on the preserved bone arrowheads shows that they were likely used for hunting difficult-to-catch rainforest prey. Not only that, but the scientists show that other bone tools may have been used for making nets or clothing in tropical settings, dramatically altering traditional assumptions about how certain human innovations were linked with specific environmental requirements.

Hunting in the open and sheltering from the cold?

European cultural products in the form of cave art, amazingly detailed bone carvings, bone tool technologies, and tailored clothing have been frequently held up as the pinnacle of Late Pleistocene human cultural development. There, symbolic and technological innovations have been seen as key survival mechanisms equipping expanding populations to face cold northern climates. Meanwhile, discoveries of older bow-and-arrow technology and artistic or symbolic behaviors in open grassland or coastal settings in Africa have framed 'savannah' and marine environments, respectively, as key drivers behind early hunting and cultural experiments by Pleistocene humans in their evolutionary homeland.

As co-author of the new study, Patrick Roberts of the MPI-SHH argues that "this traditional focus has meant that other parts of Africa, Asia, Australasia, and the Americas have often been side-lined in discussions of the origins of material culture, such as novel projectile hunting methods or cultural innovations associated with our species." Nevertheless, the last twenty years have highlighted how Pleistocene humans occupied and adapted to a variety of extreme environments as they migrated beyond Africa, including deserts, high-altitude settings and tropical rainforests such as those of Sri Lanka.

A tropical home

The new study saw scientists turn to the beautifully preserved material culture from the cave of Fa-Hien Lena, deep in the heart of Sri Lanka's Wet Zone forests. As co-author Oshan Wedage, PhD at MPI-SHH, states, "Fa-Hien Lena has emerged as one of South Asia's most important archaeological sites since the 1980s, preserving remains of our species, their tools, and their prey in a tropical context." Some of the main finds from the site include remarkable single and doubled pointed bone tools that scientists had suspected were used in the exploitation of tropical resources. Direct proof had been lacking, however, in the absence of detailed high-powered microscopic analysis.

Michelle Langley of Griffith University, the lead author of the new study, is an expert in the study of microscopic traces of tool use and the creation of symbolic material culture in Pleistocene contexts. Applying cutting edge methods to the Fa-Hien Lena material confirmed the researchers' hypothesis. As Langley states, "the fractures on the points indicate damage through high-powered impact - something usually seen in the use of bow-and-arrow hunting of animals. This evidence is earlier than similar findings in Southeast Asia 32,000 years ago and is currently the earliest clear evidence for bow-and-arrow use beyond the African continent."

The evidence for early human innovation did not stop there. Applying the same microscopic approach to other bone tools, the team identified implements which seem to have been associated with freshwater fishing in nearby tropical streams, as well as the working of fiber to make nets or clothing. "We also found clear evidence for the production of colored beads from mineral ochre and the refined making of shell beads traded from the coast, at a similar age to other 'social signaling' materials found in Eurasia and Southeast Asia, roughly 45,000 years ago," says Michelle Langley. Together, this reveals a complex, early human social network in the tropics of South Asia.

A flexible toolkit for new hunting grounds

The new study highlights that archaeologists can no longer link specific technological, symbolic, or cultural developments in Pleistocene humans to a single region or environment. "The Sri Lankan evidence shows that the invention of bows-and-arrows, clothing, and symbolic signaling occurred multiple times and in multiple different places, including within the tropical rainforests of Asia," says co-author Michael Petraglia of the MPI-SHH. In addition to insulation in cold environments, clothes may have also helped against tropical mosquitoes, "and instead of just hunting large grassland mammals," adds zooarchaeologist Noel Amano, another MPI-SHH co-author, "bows and arrows helped humans procure small, tree-dwelling primates and rodents."

While archaeologists have long focused on the uniqueness of European markers of behavioural modernity, the new study is part of a growing awareness that many regions of the world saw extraordinary and complex new technologies emerge at the end of the Palaeolithic. "Humans at this time show extraordinary resourcefulness and the ability to exploit a range of new environments," notes Nicole Boivin, Director at the MPI-SHH and study coauthor. "These skills enabled them to colonize nearly all of the planet's continents by about 10,000 years ago, setting us clearly on the path to being the global species we are today."

Mixture and migration brought food production to sub-Saharan Africa

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."