Does this ancient DNA from a Neanderthal bone hold evidence of a lost human tribe and potentially rewrite the beginnings of humanity?
A femur found in a southwestern Germany cave offered scientists firm proof that a small human group left Africa and disappeared long before the major migration that spearheaded the modern diverse populations around the globe.
Mysterious Early Human Migration
At present, experts agree that Homo sapiens evolved at least 300,000 years ago in the African continent. About 70,000 years ago, a small population became established there and gave rise to populations of people known today.
Dr. Johannes Krause, director of the Max Planck Institute for Human History in Germany, wondered about the glaring gap.
“Why did people not leave Africa before?” he wondered, especially considering Africa’s physical link to the Near East.
Now in a new study, Krause and his colleagues reported that Africans actually moved out around 270,000 years ago. He deemed it a “comprehensive picture" now since they concluded how a wave of early human relatives moved from Africa to Europe, interbreeding with Neanderthals.
While the African migrants vanished, some of their mitochondrial DNA was left traceable in later Neanderthal generations.
Mitochondria are inherited from mothers to children and can be used for tracing maternal lineages as well as population split times. Changes from mitochondrial DNA mutations, which occur at predictable rates, can be used for distinguishing groups and estimating the length of time that has passed since two people shared a common ancestor.
Complicated Neanderthal-Modern Human Links
Neanderthals have a complex relationship with modern humans, where paleontologists have struggled since the 1800s to determine their relations. The oldest Neanderthal-like bones, detected in a Spanish cave, date back 430,000 years and suggest their ancestors left Africa almost half a million years ago and ventured across Europe before they died out some tens of thousands of years ago.
Modern humans’ ancestors, on the other hand, migrated out of Africa some 50,000 years ago before spreading out. DNA from modern humans with non-African lineage revealed genes that had evolved in Neanderthals and Denisovans — telling of an on-off intermingling in Europe for a few thousand years.
Yet something about the new discovery didn’t fit the accepted picture.
"The bone, which shows evidence of being gnawed on by a large carnivore, provided mitochondrial genetic data that showed it belongs to the Neanderthal branch," explained lead author Cosimo Posth in a statement.
These mitochondria did not emerge from the same group as those that belong to other previously studied Neanderthal bones but instead came from a lineage that dated back 220,000 years. This suggested that modern humans might have had a quick “rendezvous” with Neanderthals in Europe long before the established wave of migration leading to today’s population.
Here’s the important piece of the puzzle based on the new evidence: about 450,000 years ago, a Neanderthal-Denisovan ancestor ventured off to Europe and Asia. Those who went further east became the Denisovans, while those who went west became the Neanderthals.
Some 200,000 years ago, a small group from the modern humans’ ancestral line left Africa and bred with Neanderthals. They managed to leave their mitochondria but didn’t leave a notable mark on the nuclear DNA of the Neanderthals.
The newly discovered human group is deemed more closely related to modern humans than Neanderthals.
This fitting finding, or the fossil bone, comes from another distinct group that migrated from Africa.
The study was detailed in the journal Nature Communications.