For many years, scientists have searched for evidence to explain how modern humans evolved and where we truly come from. The most accepted story said that Homo sapiens appeared in Africa, spread across the world, and mixed with other species like Neanderthals and Denisovans. Those encounters left traces of ancient DNA that people outside Africa still carry today.
However, new evidence suggests the story of humanity is far more complex — and that millions of people may have inherited the DNA of a mysterious human ancestor who vanished more than 600,000 years ago. So, let’s learn more about this.
Our DNA
The discovery was made by scientists Arun Durvasula and Sriram Sankararaman from the University of California, Los Angeles (UCLA). Their study, published in Science Advances, found evidence of a “ghost lineage” — a lost group of ancient humans that once lived in Africa and mixed with the ancestors of modern West Africans.
What makes this discovery amazing is that this unknown group doesn’t match any species we know. It’s not Neanderthal, not Denisovan, or any other known human type. It seems to come from a completely different branch of humanity — one that disappeared long ago but left traces of itself in our DNA.
DNA instead of bones
This discovery didn’t come from fossils or old bones, but from genetic evidence hidden in the DNA of people today. Scientists studied the genes of four African populations, including the Yoruba people from Nigeria.
When they compared this DNA to known human species, they found something surprising — between 2% and 19% of it didn’t match any species we know. This means those genes came from an unknown ancestor who separated from the human family more than 600,000 years ago, long before the Neanderthals or Denisovans appeared.
Because Africa’s heat and humidity destroy old DNA, it’s almost impossible to find fossils that still have genetic material. So, scientists created a new method to spot genetic evidence of mixing between species — tiny pieces of DNA that don’t match the rest, like fingerprints from a lost ancestor.
The hidden evidence
Some of this ancient DNA didn’t just survive — it may still help people today. The scientists found traces of the unknown ancestor’s DNA in a gene called NF1, which helps protect against tumors. This gene appears unusually often in several African populations. That suggests that natural selection kept some of this ancient genetic evidence because it gave humans an advantage for survival.
Similar patterns have been seen with Neanderthal DNA in Europeans and Asians. Their inherited genes improved their immune systems and helped them fight off infections. In Africa, these genetic adaptations may have also helped humans survive in changing and challenging environments.
Still, not all of the ancient DNA was useful because much of it disappeared over time, which shows that children born from these interspecies crossings were not always fully viable. But the evidence that remains helps scientists fill in the missing pages of human evolution.
Who was this unknown ancestor?
That’s hard to know, because without fossils or DNA samples, it’s like trying to guess what someone looks like just from their shadow. Impossible, right?
Some scientists think it could have been Homo heidelbergensis, a strong and intelligent species that lived in Africa around 200,000 years ago and might have been the ancestor of both Neanderthals and modern humans.
Others believe it may have been a group of early Homo sapiens who lived alone in West Africa for thousands of years, evolving in a different way from the rest of humanity.
Africa
This discovery gives scientists a new way to see human evolution — not as a straight line, but as a web of connections. Africa wasn’t just one place where humans began, but a mix of many different groups that evolved, mixed, and sometimes disappeared over time.
The old idea that humans came from just one place is now changing. Scientists now believe that many human groups lived, mixed, and shared genes, leaving traces of their connection in our DNA.
The evidence that changes everything
Today, millions of people in West Africa carry genetic evidence of that ancient encounter with an unknown human species. An encounter that left no bones, only descendants. And that evidence forever changes our understanding of who we are and where we come from.