The ancestors of all modern humans separated from a mystery population 1.5 million years ago, then reconnected with them 300,000 years ago, suggests a new genetic model. The unknown population has contributed 20% of our DNA and may have stimulated the brain function of humans.
“The fact that we can rebuild the events of hundreds of thousands or millions of years just by looking at DNA today is surprising, and that tells us that our history is much richer and more complex than we imagined”, co-author of study Aylwyn scalllyA geneticist at Cambridge University, said in a statement.
In a study published Tuesday, March 18 in the journal Nature geneticsThe researchers presented a new method of modeling genomic data, called “cobraa”, which allowed them to trace the evolution modern humans (Homo sapiens).
By applying their new method to modern human DNA data published in the 1000 Genomes project and the human genome diversity project, the researchers discovered that there were two main ancestral groups which divided approximately 1.5 million years ago, which they called population A and population B.
Just after this split, the population experienced a bottleneck when the population has dropped and has probably lost a significant amount of genetic diversity. But the population has grown over time, and Neanderthal And Denisovans branched from it.
In relation: Human ancestors arrived in Western Europe much earlier than it was thought before, fossil face fragments reveal
Then, about 300,000 years ago, the population was mixed with the B population, revealed the researchers. Their genetic analysis suggests that 80% of the genome of all current humans comes from the population A, while 20% of our genome comes from the B population.
Some of the genes of the population B, “in particular those linked to brain neuronal function and treatment may have played a crucial role in human evolution, “co-author of the study Trevor CousinsA third cycle student in genetics at the University of Cambridge, said in the statement. In general, the genetic material of population B has reduced the ability of individuals to have children, said cousins to living science in an email, but “genome is a complicated place, and regions outside the genes can still do important things”.
The new model suggests that, about 300,000 years ago, the population A, which finally gave birth to humans, had a “deep structure”, said Cousins, which means that it was formed from “two or more genetically distinct populations that mixed”.
Who these populations were, however, is not clear. In the study, researchers noted that ” Homo erectus And Homo heidelbergensis The populations who are potential candidates for lines A and B existed both in Africa and elsewhere in the relevant period. “”
But “the genetic model cannot indicate which fossils should be attributed to the population A or B,” said Cousins. “We can only speculate.”
Some experts use the term “ghost populations” to talk about groups that have extended, then reconnected later thanks to interdependence, which led to a flow of genes, John HawksAn biological anthropologist at the University of Wisconsin-Madison who was not involved in the study, said in Live Science by e-mail.
“What is interesting in this article is that the model of the model is a deep African structure shared by all those who live today,” said Hawks. “It is not” ghost populations “that contribute to a particular group, it is a large ghost who merged with the population of African source for all modern humans.”
But one of the drawbacks of the new model, according to the Hawks, is that it is based on the 1000 Genomes project, which has a low representation of the African populations. “So I consider it as proof of principle that a real guide of what ancient humans did,” said Hawks.
The origin of modern humans is a long -standing question of paleoanthropology, and improvements in DNA and genomic analysis in the past two decades have provided new ideas and raised new questions.
“What becomes clear is that the idea of species evolving in clean and distinct lines is too simplistic,” Cousins said in the press release. “Burial and genetic exchange have probably played a major role in the emergence of new species several times through the animal kingdom.”