Some modern humans have DNA from a still unknown ancestor

A new analysis of ancient genomes suggests that the different branches of the human family tree crossed several times, and that Some people carry DNA from an archaic and unknown ancestor. Melissa Hubisz and Amy Williams from Cornell University and Adam Siepel from the Cold Spring Harbor Laboratory report on these results in an im PLOS Genetics Magazine.

About 50,000 years ago a group of people emigrated from Africa and their components mixed with them Neanderthals in Eurasia. But it’s not the only time our ancient human ancestors and their relatives exchanged DNA. Genome sequencing of Neanderthals and a lesser known ancient group, the Denisovanshas produced much new knowledge about these crossbreeding events and the movement of ancient human populations.

According to the new article, the researchers developed a genome analysis algorithm that can do this Identify DNA segments They are from other species, even if this gene flow occurred thousands of years ago and came from an unknown source. They used the algorithm to study the genomes of two Neanderthals, one Denisovan, and two African humans. The researchers found evidence that 3 percent of the Neanderthal genome came from old people, and they estimate that the crossbreed occurred 200,000 to 300,000 years ago. In addition, it is likely that 1% of the Denisovan genome came from an unknown and more distant relative, possibly Homo erectus, and around 15% of these “superarchaic” regions may have been passed on to modern humans living today. in day.

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Neanderthal woman. (Photo: Pixabay)

The new results confirm previously reported cases of gene flow between old people and their relatives, and also point to new cases of crossbreeding. Given the number of these events, the researchers say that genetic exchange was likely as long as two groups overlapped in time and space. His new algorithm solves the difficult problem of identifying tiny remnants of gene flow that appeared hundreds of thousands of years ago when only a handful of ancient genomes were available. This algorithm can also be useful to study gene flow in other species that have crossed, such as B. wolves and dogs.

“What I find exciting about this work is that it shows what can be learned about deep human history by working together to reconstruct the entire evolutionary history of a collection of sequences from both modern humans and archaic hominids,” said author Adam Siepel. “This new algorithm that Melissa developed that ARGweaver-Dis able to go further back in time than any other calculation method I’ve seen. It seems to be particularly powerful at recognition Introgression ancient. “(Source: NCYT amazement)

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