Scientists have discovered DNA from two unknown ancient human species within the genetic code of people living today. Researchers at the University of California, Berkeley, used a new computer tool called TRACE to analyze modern human genomes. This tool helped them find genetic material from ancestors that science has never seen before.
The study, published in the journal Science, found that about two percent of the DNA in today's humans comes from these two ancient groups. One group, called a "ghost" lineage, separated from modern humans around 800,000 years ago. This mixing happened in Africa before humans spread across the world, so this DNA is found in everyone.
Another discovery is a "super-archaic" lineage that split off from our ancestors about 1.8 million years ago. This group mixed with Denisovans, another ancient human group, over 200,000 years ago. When Denisovans later interbred with modern humans, they passed on a small amount of this very old DNA. This ancient DNA is most common today in people from Oceania.
Researchers believe this ancient DNA helped our ancestors survive. It is found in parts of our genes related to fighting diseases and processing food. This suggests that mixing with other ancient human groups gave early humans important genetic advantages to adapt to new environments and challenges. The findings show that human evolution was more complex than previously thought, like a web of connections rather than a simple family tree.