Ghost Human Ancestor's Near-Full Genome Found in Us
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- Yulin Zhang and Priya Moorjani at UC Berkeley report that 0.5–1% of any living person's DNA traces back to a previously unknown 'ghost ancestor,' with fragments spread evenly enough across the genome that nearly its entire DNA could theoretically be reassembled from modern humans alone.
- The team's new computational method constructs a 'family tree' of genomic segments and was validated by correctly identifying Neanderthal and Denisovan DNA from modern human genomes alone, with no fossil reference required.
- The more recent ghost ancestor split from the main human lineage roughly 800,000 years ago and likely interbred with Homo sapiens in Africa; the researchers speculate it may be Homo heidelbergensis, which fossil evidence places in Africa as recently as 300,000 years ago.
- A second, far older 'super-archaic' lineage split off around 1.8 million years ago and interbred with Denisovans in Eurasia, leaving traces in modern humans that reach us only via Denisovan gene flow.
- Chris Stringer at London's Natural History Museum called the work important and innovative, identifying the super-archaic candidate as most likely Homo erectus and praising the method as a way to reconstruct genomes of species for which no fossil DNA exists.
- Unlike Neanderthal and Denisovan DNA — which is largely absent from long stretches of the modern genome because those small populations carried detrimental mutations and were selected against — the ghost ancestor's DNA was preserved at much higher rates, suggesting its population was substantially larger.
Why it matters: The Berkeley team's method lets scientists reconstruct the genome of an extinct human species from modern human DNA alone, with no fossils required. That opens a window onto lineages like Homo erectus and Homo heidelbergensis that left no usable ancient DNA, turning living people into a genetic archive for human ancestors researchers previously thought were lost.
