Researchers identify traces of two ‘ghost’ ancestors in modern human DNA

Key Points:

• Scientists have identified two previously unknown ancestral human lineages, or "ghost" populations, through analysis of modern human genomes using a new method called TRACE, which reconstructs genealogies from living people’s DNA.
• One lineage interbred directly with Homo sapiens in Africa over 50,000 years ago and contributes about 0.5% to 1% of DNA in present-day humans, while the other is a much older "super-archaic" lineage that interbred with Denisovans more than 200,000 years ago, indirectly passing DNA to modern humans.
• The younger lineage may be linked to Middle Pleistocene Homo populations such as Homo heidelbergensis in Africa, and the older lineage could be related to Homo erectus from Eurasia, though no DNA from these groups has yet been recovered from fossils.
• This discovery sheds light on the complex interbreeding history of human ancestors, highlighting genetic contributions from multiple extinct hominin groups and offering insights into human evolution, adaptation, and disease susceptibility.
• Researchers hope TRACE will reveal more hidden lineages across species, but emphasize that extracting DNA from ancient fossils remains critical for confirming these findings.