Researchers have used a novel computer‑based technique called TRACE to scan more than 500 modern human genomes from Africa, Europe and Asia. The analysis uncovered genetic traces of two “ghost” ancestors that left no fossil DNA but are now detectable in living people.
Recent African interbreeding
The first lineage appears to have interbred directly with Homo sapiens in Africa more than 50,000 years ago, before our species migrated out of the continent. DNA from this group makes up roughly 0.5% to 1% of the genomes of people today—about the same proportion as Neanderthal DNA in many populations.
A “super‑archaic” lineage linked to Denisovans
The second, older lineage diverged from the human family tree about 1.8 million years ago. Researchers believe it mixed with Denisovans in Eurasia over 200,000 years ago, and some of its DNA later entered modern humans through the later Denisovan‑human interbreeding.
Implications for science and health
Co‑author Priya Moorjani of UC Berkeley said the findings help answer long‑standing questions about why some ancient hominin groups survived while others vanished. Understanding these deep ancestral contributions may also shed light on how ancient genetic variation influences modern disease susceptibility.
While the exact identities of the ghost groups remain uncertain, the study suggests they could be related to Middle Pleistocene Homo populations such as Homo heidelbergensis in Africa and possibly Homo erectus in Eurasia. No DNA has yet been recovered from those fossils.
The TRACE method reconstructs genealogical maps that show where different DNA fragments originated, allowing scientists to piece together parts of the human family tree that are missing from the fossil record. The researchers hope the technique will uncover additional hidden lineages in both humans and other species.
Original reporting: KRDO (Colorado Springs metro) — read the source article.
