Ancient DNA Is Rewriting Human History — And Scientists Can’t Keep Up

Finding out that about 1% of your genome belongs to someone scientists can’t quite name is a little unsettling, but in the best way possible. There are no known fossils. Not a face. No one has fully agreed on a species name. It was only a genetic signal, spread out in the human genome like graffiti from a culture that vanished before anyone could write it down.

That’s pretty much what a new study that came out on July 30, 2026, in Science says. UC Berkeley researchers created a computer method called TRACE, which stands for “Tracking Archaic Contributions via ARG Estimation.” They used it to look through more than 500 full modern human genomes. What they found has been getting a lot of attention in the field of evolutionary genetics, and it probably should be getting more attention everywhere else too.

In short, modern humans have DNA from at least two ancestral groups that haven’t been fully characterized yet. One bred with our species in Africa more than 50,000 years ago, long before the most recent wave of people left the continent. People today, African and non-African alike, have DNA from this species. It makes up about 0.5% to 1% of our genomes. About 800,000 years ago, around the same time that Neanderthals and Denisovans split off, the lineage seems to have become separate from the human family tree. A species called Homo heidelbergensis is often put forward as a possibility. This species lived in Africa and Europe until about 200,000 years ago. It’s still not clear if that identification will hold up, but the genetic timeline makes sense.

The second family tree is even stranger. It is only found in people from Oceania, which are the island nations of the Pacific. It is nested inside parts of Denisovan DNA, which suggests it got to humans through a middleman. Our best guess is that this “super-archaic” lineage is about 1.8 million years old. That’s old enough to include Homo erectus, which is the oldest known species of human, and the link is more than just a guess: Denisovan remains and H. erectus skulls found in China have a lot in common. This case is still not over. The genetics point in a certain direction, but the fossil record hasn’t fully proven it yet.

The method itself is what makes this study worth your time. Prior research on ancient interbreeding relied on directly extracting DNA from fossils, which needs very specific preservation conditions. This means that the fossils had to be found in cold, dry places in the north. A tough case is Africa, where a lot of human evolution took place. DNA breaks down faster in warm, humid places. That’s why the record has always been skewed toward the groups that buried their dead in Siberian caves. TRACE completely avoids that issue. It doesn’t need bones. It re-creates family trees from the genomes of living people by finding stretches of DNA that have ancestry that goes back an unusually long time. These are markers that the algorithm sees as coming from very different populations.

In the last ten years or so, the field of ancient DNA has moved very quickly. In the 1980s, the first ancient DNA sequences were found in quagga hides and Egyptian mummies. However, most of them turned out to be contamination. In the 2010s, researchers sequenced the Neanderthal genome, which confirmed what many people had long thought: that our species and theirs had shared more than just a campfire at some point. Most people who are not African have between 1% and 2.4% Neanderthal DNA in their bodies. On top of that, Asians and Pacific Islanders have Denisovan ancestry.

The things that have been found so far might only be the start of a much longer list. These old segments are disproportionately common in immune-related parts of the human genome. This suggests that our ancestors didn’t just occasionally meet these other groups; they took useful genes from them and kept them. Adaptation that came from different species. That’s not the picture most people have in their minds of how humans evolved. It won’t be a neat tree with branches like a family tree, but something messier and more collaborative.

As you read this, you get the sense that the common story of how humans came to be has been quietly taken apart and put back together more than once in the last twenty years, each time making it a little more complicated, a little less certain, and a lot more interesting.

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