Scientists Identify Two Previously Unknown Human Ancestor Lineages in Modern DNA

Researchers have used a novel computer-based approach, called TRACE, to scan more than 500 modern human genomes from Africa, Europe and Asia. The analysis uncovered genetic signatures of two previously undetected ancestral lineages. One lineage appears to have mixed with early Homo sapiens in Africa more than 50,000 years ago, contributing roughly 0.5% to 1% of the DNA of contemporary peoples. The second, termed a “super-archaic” lineage, diverged from the human family tree about 1.8 million years ago and likely interbred with Denisovans in Eurasia over 200,000 years ago, passing some of its DNA to modern humans through that route.

"The most fundamental question that most of us have is, ‘Why are we here? Where do we come from?’ And these genealogies really allow us to look into the past in a way that we have not been able to do before," said Priya Moorjani, coauthor and associate professor at the University of California, Berkeley.

"The super-archaic finding is particularly exciting because it reveals genetic contributions from a human lineage that lived over a million years ago, despite the absence of any sequenced DNA from that population," said Arjun Biddanda, co-first author of the study.

The researchers suggest the younger lineage could correspond to Middle Pleistocene Homo populations in Africa, possibly Homo heidelbergensis, while the older lineage may be related to Homo erectus from Eurasia. No DNA from these groups has yet been recovered from fossils. Paleoanthropologist John Hawks, who was not involved in the study, noted that the newly identified admixture predates the well-documented Neanderthal mixing and is present across all modern populations.

The team hopes TRACE will enable further discovery of hidden lineages in both humans and other species, though they acknowledge that direct ancient DNA remains the gold standard for confirming such relationships.