Updated July 16, 2021 at 8:30 p.m.

  • About 600,000 and 200,000 years ago, the genetic makeup of modern humans changed significantly, according to a new study.
  • Researchers have developed a new analysis method with which they can calculate when and which changes in the genetic material occurred.

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Important changes in the genetic makeup of modern humans may have occurred around 600,000 and 200,000 years ago. This is the result of an analysis of 279 genomes from today, two genomes from Neanderthals and one genome from Denisovans.

Most genetic changes affect the development and function of the nerves and brain. The study by a research group led by Richard Green from the University of California Santa Cruz (California, USA) has appeared in the journal “Science Advances”.

When did what changes in the genetic material occur?

“Much of the current genetic variation within humans can be traced back to the split between populations that became modern humans and Neanderthals, estimated 520,000 to 630,000 years ago,” the scientists write.

However, it is often difficult to distinguish which genes go back to common ancestors of Homo sapiens and Neanderthals and which later entered the gene pool of modern humans through common descendants of the two.

Green and colleagues therefore developed a new analysis method with which they can create gene maps: These maps show which genes the different groups of modern humans share with the Neanderthals and Denisovans.

Statistical methods can then be used to calculate when and which changes in the genetic material occurred. Their method is less fine than others, but it works particularly well at high mutation rates, the researchers write.

Many genes are associated with nerves and the brain

They examined the genetic material carriers, more precisely the chromosomes without the sex chromosomes, and found regions in which no genes could be found that modern humans share with the Neanderthals or the Denisovans. This was about 7 percent of the genome.

If Green’s team narrowed down the regions to particularly common variants of genes (alleles), then these regions only made up 1.5 percent of the genome of modern humans. The geneticists therefore assume that between 1.5 and 7 percent of the genome is specific for modern humans.

The study authors also looked at which genes were located in the typical human gene regions. They found, among other things, two genes that are mainly read in brain tissue and one gene that guides nerve fibers. Overall, many of the genes are connected to the nerves and the brain, which suggests that these areas of the body developed to a particular degree during the evolution of Homo sapiens.

Timing of genetic changes

Finally, the scientists analyzed when these genetic changes occurred. The focus was around 600,000 years ago.

They also examined which other genes the genes found interacted with and determined the age of their mutations: it was mainly around 200,000 years. During these times, many genetic changes may have occurred that led to modern humans. (ff / dpa)

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