Researchers have announced that they have successfully sequenced the entire genome of a man who lived 4,500 years ago, making it the oldest human genome ever sequenced. The results were published in the journal Science.
This important achievement is already yielding vital information about human history, and specifically a long hypothesized Eurasian migration through which Eurasian farmers migrated back into Africa.
The reason scientists were able to do so was because they found a specimen buried, face down, in a cave in the Ethiopian highlands. The cave was called “Mota” and some have taken to calling the man Mota.
Most of Africa is hot and humid, thus making preservation difficult, if not impossible. The Ethiopian Highlands, however, are cool and dry, allowing much of the genetic material to be preserved.
This specimen was surprisingly well preserved and scientists were able to extract a huge amount of genetic data. The DNA was taken from the skull’s thick petrous bone.
Mota cave, by the way, sits approximately 6,500 feet in the air. Mota himself was found buried in a ceremonial fashion.
The most important discovery of the recent genome sequencing is the extent and nature of the so-called “Eurasian backflow“, in which people from Anatolia, the Middle East, and elsewhere flowed back to the horn of Africa, where man first appeared.
According to data uncovered from the sequencing of the African man, this backflow was far more significant than previously thought. As a statement from the research team puts it, the backflow “was up to twice as significant as previously thought, and affected the genetic make-up of populations across the entire African continent.”
Scientists were able to compare genetic information from the ancient remains to modern East Africans, and have concluded that as much as 25 percent of their genetic ancestry comes from the so-called backflow.
In fact, scientists found that samples from every single person for which they have data actually had some Eurasian DNA. Previously, researchers had believed that the re-migration had had a much smaller impact on Africa, but the Mota discovery has up-ended this long-held theory.
As of right now, however, scientists believe that most Africans outside of the Horn of Africa region trace less of their heritage from the Eurasian backflow. Regardless, evidence suggests that Eurasian DNA made it deep into the heart of Africa, albeit only in single digit percentages.
While those Africans who live on on the horn of Africa share the most DNA with Eurasians, scientists found traces of Eurasian DNA across most of the continent. Even the relatively isolated such as Yoruba and Mbuti tribes showed surprisingly high levels of Eurasian DNA, as high as 7 percent.
As a result, scientists will have to go back to the drawing board and rethink the African migrations.
Most scientists currently believe that humans originated in Africa, and then migrated into the Middle East, Europe, and beyond. At some point, however, scientists believe that some people across Eurasia migrated back. Many others migrated to Asia, Oceania, and eventually the Americas.
Previously, scientists have been able to recover genetic materials from humans, but usually from cooler regions. Cooler climates are far more conductive for preserving genetic materials than the hot, and often humid regions of Africa.