The DNA that makes us uniquely human can be found in small pieces that are inserted among what we inherited from our extinct ancestors. Those little pieces don’t add up to much else. Perhaps only 1.5-7 percent of our genetic instruction manual, or genome, is uniquely human. The researchers shared their new discovery on July 16 Science Advances.
This uniquely human DNA tends to contain genes that influence how the brain develops and functions. And this suggests that brain evolution is the key to what makes us human. But the new research still doesn’t show exactly what they do the uniquely human genes. In fact, two extinct human cousins, Neanderthal and Denisova, may have had thoughts very similar to ours.
“I don’t know if we’ll ever be able to say what makes us uniquely human”, says Emilia Huerta-Sanchez. “We don’t know if this makes us think in a specific way or have specific behaviors”says this population geneticist. He works at Brown University in Providence, RI, where he did not take part in this new job.
Researchers at the University of California, Santa Cruz used computers to study human DNA. They have studied every point in the genomes of 279 people. At each point, the team found out whether that DNA came from Denisova, Neanderthal, or other hominids. Based on these data, they compiled a map of our general mix of genes.
On average, most African people inherited up to 0.46 percent of their DNA from Neanderthals, according to the new study. This was possible because thousands of years ago, humans and Neanderthals mated. Their children inherited some of that DNA. Then they continued to pass on parts of it to the next generation. Non-Africans tend to carry more DNA than Neanderthals: up to 1.3%. Some people even have some Denisovian DNA.
Each person’s DNA can be about 1% Neanderthal. Still, looking at several hundred people, says Kelley Harris, most of them “He will not have his share of Neanderthal DNA in the same place”. Harris is a population geneticist. He works at the University of Washington in Seattle. However, he did not work on this project.
When you add up all the places someone has inherited Neanderthal DNA, that makes up a large part of the genome, he says. The researchers found that about half of that genome has points where someone in the world could have the DNA of a Neanderthal or a Denisovan.
Like all cousins, humans, Neanderthals and Denisovas they had common ancestors. Each of the cousins inherited some DNA traits passed down from those ancestors. That DNA makes up another big chunk of the genome.
The new study explored regions where all people have DNA changes not found in any other species. This showed that between 1.5% and 7% of our DNA appears unique to humans.