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WE LEARN about our ancestors in many ways.
Bones tell us what they looked like. Teeth reveal their diet. Tools, pots, art and other artefacts hold stories about their culture. Then, a decade ago, the first ancient genome was sequenced, opening a whole new window on our past – one that promised more intimate insights.
The breakthrough famously revealed that Neanderthals got very cosy with humans. Since then, geneticists have been probing more and more fossils for evidence of past cross-species dalliances. The studies haven’t disappointed. But in an intriguing twist, they have started to kick up something unexpected: hidden inside genomes are signs of ancestors that we never knew existed. Geneticists call them “ghosts”.
We have no physical record of these ancient hominins – no bones, no tools, no archaeological remains whatsoever. Yet the genetic code that they left within fossils of other hominins, and in living humans too, is offering profound and unprecedented insights into how our species came to be, and what the world was like at the time.