UC Berkeley researchers led by geneticist Priya Moorjani have developed a new computational method, called TRACE, that pinpoints DNA modern humans inherited from two previously unknown extinct hominin lineages — without needing any ancient DNA samples.
One "ghost" ancestor interbred with modern humans in Africa more than 50,000 years ago, before the major human migration out of the continent. Its DNA makes up roughly 1% of the genome in people from every population studied, comparable to the amount of Neanderthal DNA most non-Africans carry. This lineage split from the modern human line about 800,000 years ago — around the same time Neanderthals and Denisovans branched off.
A second, far older "super-archaic" ancestor traces back roughly 1.8 million years. It interbred with Denisovans over 200,000 years ago, who then passed that DNA on to modern humans — showing up mainly in Oceanian populations today. Altogether, about 2% of modern human genomes come from archaic hominins whose fossils have never been found.