For almost a century, Neandertals were considered the ancestors of modern humans. But in a new plot twist in the unfolding mystery of how Neandertals were related to modern humans, it now seems that members of our lineage were among the ancestors of Neandertals. Researchers sequenced ancient DNA from the mitochondria—tiny energy factories inside cells—from a Neandertal who lived about 100,000 years ago in southwest Germany. They found that this DNA, which is inherited only from the mother, resembled that of early modern humans.

After comparing the mitochondrial DNA (mtDNA) with that of other archaic and modern humans, the researchers reached a startling conclusion: A female member of the lineage that gave rise to Homo sapiens in Africa mated with a Neandertal male more than 220,000 years ago—much earlier than other known encounters between the two groups. Her children spread her genetic legacy through the Neandertal lineage, and in time her African mtDNA completely replaced the ancestral Neandertal mtDNA.

Other researchers are enthusiastic about the hypothesis, described in Nature Communications this week, but caution that it will take more than one genome to prove. “It’s a nice story that solves a cool mystery—how did Neandertals end up with mtDNA more like that of modern humans,” says population geneticist Ilan Gronau of the Interdisciplinary Center Herzliya in Israel. But “they have not nailed it yet.”

The study adds to a catalog of ancient genomes, including mtDNA as well as the much larger nuclear genomes, from more than a dozen Neandertals. Most of these lived at the end of the species’ time on Earth, about 40,000 to 50,000 years ago. Researchers also have analyzed the complete nuclear and mtDNA genomes of another archaic group from Siberia, called the Denisovans. The nuclear DNA suggested that Neandertals and Denisovans were each other’s closest kin and that their lineage split from ours more than 600,000 years ago.

[Source”timesofindia”]