Pre-colonial African history is replete with tales of the rise and fall of civilizations and different cultures mixed across the continent. We have now shed more light on some of these communities that use genetics.
in a study Posted in Science advancesMy co-authors and I have used DNA information from people from the present-day continent to highlight important pre-colonial civilizations. Genetic information was extracted from the blood samples by machines. Once we have read the sequence of “letters” in the DNA code or sequence, we can use computers to compare the genetic differences and similarities between the populations in the study.
One startling finding concerned two ethnic groups in the north of present-day Cameroon, in West and Central Africa, the Kanuri and Kotoko peoples. We found that these two groups are descended from three ancestors.
These ancestral groups were very similar to the people who now live in the coastal regions of West Africa as well as in parts of East Africa such as Ethiopia and the populations living today in North Africa and the Levant. The population mixed—they have children together—about 600 years ago. But what made them migrate thousands of kilometers across the desert to northern Cameroon?
We think the answer is Kanem-Bornu Empire, a civilization that has existed for more than 1,000 years – starting around 700 AD. At its height, the empire extended to what is now northern Cameroon, northern Nigeria, Chad, Niger, and southern Libya. It operated vast trading networks across the desert and attracted inhabitants from every direction.
This example highlights how our genomes contain information about major events in the past. Merchants traveling along trade routes or forming empires from smaller political units can leave footprints in our DNA. previous job Offers that Roman Empirethe Mughal EmpireAnd Silk Road trade All may have left a lasting legacy in the genomes of modern people across Eurasia.
hidden in the genome
We analyzed 1,300 newly collected genomes of people from all over Africa. They came from 150 ethnic groups in five countries. We have collaborated with anthropologists, archaeologists, and linguists from Africa and elsewhere. They helped us understand the historical context of these events.
African genome data underrepresented compared to other regions of the world. This means that much of the genetic diversity — or diversity — in the DNA of populations has likely been missed by scientists.
Studying genetic diversity has many potential uses – such as understanding risks to health and developing new treatments for disease. Our group was interested in genetic diversity as a window into the past.
We modeled a person’s genome as a mixture of DNA fragments inherited from their ancestors. If a person has pieces of DNA that closely match two groups of people – for example, Europeans and West Africans – this indicates that that person is descended from mixing between those two groups.
The current human populations formed from a recent mixture of Europeans and West Africans must contain long fragments of DNA from both groups. The segments of ancestral DNA get shorter as the genetic material of their descendants is mixed with each new generation.
This provides a way to date when mixed events occurred. The longer the matching DNA fragments, for example, West Africans or Europeans, the more recent the admixture event.
Another historical event of which we find evidence is the Arab expansion into Africa. This began in the seventh century, when separate Arab armies south along the eastern coast and north from Medina in today’s Saudi Arabia crossed the Sinai Desert and invaded Egypt.
In Sudan at this time the Kingdom of Makuria It ruled along the Nile River. Makuria signed a peace agreement with the Egyptian Arabs in Egypt Mid VII century that lasted nearly 700 years.
The majority of the mixing between these two ancestral groups, one closely related to the Arabs and the other to the Sudanese, dates back to after the peace treaty began to unravel. This in turn coincided with the decline and eventual collapse of Makuria itself, which would have allowed Arab groups to continue down the Nile into Sudan.
But we also found evidence of earlier migrations to Africa from Arabia, which occurred by sea. This mixing coincided in time with Kingdom of Aksumlocated in northeastern Africa and southern Arabia, during the first millennium AD.
Aksum was once considered One of the four great powers in the worldBesides the contemporary empires of China, Persia, and Rome.
Expansion of the Bantu-speaking peoples
Genetic studies have also found evidence of a continent-wide migration known as the expansion of the Bantu-speaking peoples. Bantu is a language group that is now spoken everywhere a quarter of Africans.
There has been debate as to whether the Bantu languages were largely spread as a means of transmitting culture, or whether large-scale migration was involved. Recent research shows that the latter explanation is more likely. This migration began in a small area of western Cameroon approximately 4,000 years ago, before spreading rapidly south and east. He traveled more than 4,000 kilometers in less than 2,000 years.
Bantu speakers mixed with local groups, Changing patterns of genetic diversity in Africa Forever. We showed that migrations occurred not only to the south and east of Cameroon, but also to the west. Why so much movement occurred at this time is unknown, but climate change may have played a role.
It is imperative that scientists analyze more DNA from the genomes of Africans. As we do so, it will undoubtedly reveal a complex picture of the continent’s rich past.
Nancy Bird et al., Dense sampling of ethnic groups within African countries reveals fine-grained genetic structure and extensive historical admixture, Science advances (2023). DOI: 10.1126/sciadv.abq2616
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