Overview
- Researchers introduced TRACE, a tool that reconstructs local genealogies from modern genomes to spot unusually deep branches that signal archaic ancestry.
- Using 503 contemporary genomes the team estimated about 2 percent archaic DNA in non-Africans, split roughly as 1 percent Neanderthal, a small Denisovan fraction, and about 0.5–1 percent from an unsequenced 'ghost' lineage present in all tested populations.
- The inferred ghost lineage appears to have split from the lineage leading to modern humans more than 500,000 years ago, a timing similar to the Neanderthal–Denisovan split.
- Putative ghost segments show up even in genomic regions once thought uniquely modern, including around FOXP2, a gene linked to speech, which could change interpretations of key human traits.
- The study's authors and outside geneticists caution the result could reflect model limitations such as assumptions about demographic history, recombination and mutation-rate variation, and reference-sample gaps, so independent computational checks or ancient DNA from African fossils are required before the finding is confirmed.