A 4,500-year-old skull has produced Africa’s first ancient human genome. DNA studies suggest the Middle Eastern farmers had migrated to Africa 3,000 years ago and left traces of their Eurasian ancestry in the genomes of many Africans today.
The genome was taken from the skull of a man buried face-down in a cave called Mota, which is in the highlands of Ethiopia. Ancient genome analysis from Africa has proven to be difficult, partly because genetic material degrades quickly in hot temperatures like Africa.
The conditions in the cave were cool and dry enough for the skeleton to retain its DNA. Before this discovery, DNA samples were limited to the northern and arctic regions. This is the first study of ancient human genome that has been recovered and sequenced from Africa, which is the source of all human genetic diversity. The findings are published in the journal Science.
The ancient genome was from the bone called the petrous, which was still intact.
Dr Andrea Manica, senior author of the study, told the BBC World Service: “The petrous bone is really hard and does a really good job of preventing bacteria getting in and degrading this DNA.
“What we were able to get is some very high-quality undamaged DNA, from which we could reconstruct the whole genome of the individual. We have the complete blueprint, every single gene, every single bit of information that made this individual that lived 4,500 years ago in Ethiopia.”
The genome predates the mysterious migratory event called the “Eurasian backflow,” which is thought to have occurred around 3,000 years ago. It is believed that people from the Western Eurasia regions had suddenly returned back to the Horn of Africa.
According to phys.org, the cause of the West Eurasian migration back into Africa is a mystery, with no obvious climatic reasons. Archaeological evidence does, however, show the migration coincided with the arrival of Near Eastern crops into East Africa, such as wheat and barley, suggesting the migrants helped develop new forms of agriculture in the region.
With an ancient genome, we have a direct window into the distant past,
Dr Andrea Manica said in a statement.
One genome from one individual can provide a picture of an entire population, according to Dr Manica, who is from the University of Cambridge’s Department of Zoology.
“Roughly speaking, the wave of West Eurasian migration back into the Horn of Africa could have been as much as 30 per cent of the population that already lived there — and that, to me, is mind-blowing. The question is: What got them moving all of a sudden?” she added.
By comparing the ancient genome to DNA from modern Africans, the team has been able to show that not only do East African populations today have as much as 25 per cent Eurasian ancestry from this event, but that African populations in all corners of the continent — from the far West to the South — have at least 5 percent of their genome traceable to the Eurasian migration, the University of Cambridge wrote.
“The sequencing of ancient genomes is still so new, and it’s changing the way we reconstruct human origins,” Manica told phys.org.
“These new techniques will keep evolving, enabling us to gain an ever-clearer understanding of who our earliest ancestors were.”