Mysterious DNA: two unknown ancestors found in human genome

Scientists have discovered two previously unknown human ancestors, dubbed "ghost" and "super-archaic" lineages, whose genetic traces are present in the DNA of modern humans. These findings, published in the journal Science, suggest that early humans coexisted with multiple related hominin groups in Africa and Eurasia over the past million years.

Researchers at UC Berkeley used a new method called TRACE to identify regions of the modern human genome derived from these unidentified ancestors. One of the ghost lineages contributed approximately 1% of the modern human genome, similar to the proportion inherited from Neanderthals. The ghost lineage separated from modern human ancestors around 800,000 years ago, earlier than the interbreeding events with Neanderthals and Denisovans outside Africa.

Another study found genetic material from a super-archaic population that interbred with Denisovans in Eurasia more than 200,000 years ago. Together, these findings reveal a more interconnected history of human evolution, with numerous related human groups living alongside each other and occasionally exchanging genes. The identities of the ghost and super-archaic populations remain unknown, but their estimated separation dates align with Middle Pleistocene Homo groups in Africa and Homo erectus populations in Eurasia.