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An international team of researchers has put together a new picture of Neanderthals based on the genes that Neanderthals left in the DNA of modern humans when they had children with them about 50,000 years ago.
The researchers found the new pieces of the puzzle by tracing the genomes of more than 27,000 Icelanders. Among other things, they discovered that Neanderthal women gave birth when they were older than Homo-Sapien women at the time, and Neanderthal men became fathers when they were younger.
It is well known that a group of our ancestors left Africa and, about 50,000 years ago, met Neanderthals in Europe, and then had children with them.
Now, a new analysis shows that Neanderthals may have had children with another extinct species of human (Denisovans), before meeting Homo Sapiens, and that these children have been fertile and have later transferred genes from both species to modern people. .
The analysis also shows that Neanderthal women who lived between 100,000 and 500,000 years ago on average became mothers at an older age than contemporary homo-sapien women living in Africa. On the other hand, Neanderthal men were sired at a younger age than their Homo-Sapien cousins in Africa.
How can an analysis show all that?
Neanderthals may be extinct, but small pieces of their DNA live in us. All people living outside of Africa have up to two percent of Neanderthal genes in their DNA.
However, this two percent is scattered as small fragments in our genomes, and not all people have inherited the same fragments. The fragments are like pieces of a puzzle, and if put together correctly, they will show an image of the genome in the Neanderthal population that modern Homo Sapiens had children with.
New method to find the pieces.
First of course we have to find these pieces. And this is precisely what the group of researchers from Denmark, Iceland and Germany did to produce their results, published today in the scientific journal. Nature.
One of them, Laurits Skov, postdoc at the Center for Bioinformatics Research (BiRC) at Aarhus University, has developed a method to trace Neanderthal fragments in our DNA. Laurits and doctoral student Moisès Coll Macià brought the method to Iceland, where the CODE genetics firm has accumulated genetic data and health information for more than half of the Icelandic population.
“We spent several months at deCODE in Reykjavik in what can be called field studies for a computational biologist. Combining my method with deCODE data and experience, we have analyzed 27,566 genomes, and this makes our study 10 times larger than previous studies of Neanderthal genes in human DNA, “says Laurits Skov.
Together, the many fragments represent about half of a complete Neanderthal genome.
Are Denisovan genes missing?
However, the researchers also found significant fragments of genetic material from another archaic human species, Denisovans, in the DNA of Icelanders, and this was somewhat surprising. Until now, Denisovan genes have been found mainly in Australian Aborigines, East Asians, and people in Papua New Guinea. So how did these genes end up in the islanders’ DNA? And when?
Based on the distribution of genes and mutations, the researchers proposed two possible explanations.
Any of the Neanderthals had children with Denisovans before meeting Homo Sapiens. This would mean that the Neanderthals with whom Homo Sapiens had children were already hybrids, which transferred the Neanderthal and Denisovan genes to the children.
“Until now, we believed that Neanderthals with whom modern people had children were” pure “Neanderthals. It is true that researchers have found the remains of a hybrid between Denisovans and Neanderthals in a cave in East Asia, but not we have known if there were more of these hybrids and if, thousands of years later, they had children with modern humans. ” explains Professor Mikkel Heide Schierup from BiRC.
Or Homo Sapiens knew Denisovans long before they met Neanderthals. Until now, modern humans were thought to have known Neanderthals and had children with them first, and it was not until tens of thousands of years after they had children with Denisovans.
“Both explanations are equally likely, and both explanations will be scientific news,” says Mikkel Heide Schierup.
Neanderthal genes of little importance
The study also shows that Neanderthal DNA is not of great importance to modern humans.
“We previously thought that many of the Neanderthal variants previously found in modern human DNA were associated with an increased risk of disease. However, our study shows that human genetic variants located directly next to Neanderthal genes are better explanations for the risk. We have also found something that can only be explained by the Neanderthal genes, but this does not mean much, “says Mikkel Heide Schierup.
The properties and risks of diseases that may be related to Neanderthal DNA are: a slightly lower risk of prostate cancer, lower levels of hemoglobin, a lower body length (one millimeter) and a slight clotting of blood plasma faster.
AARHUS UNIVERSITY
Header Image: Public Domain
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