The Neanderthals did not completely disappear

2010/06/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Eboluzioa

They sequence the genome of Neandertal and compare it with that of the current man

About 30,000 years ago the man of Neanderthal disappeared. Not at all, we have their genes in our genome. To this conclusion has reached an international team of researchers, after sequencing the genome of the neanderthal and comparing it with that of the current man.

The study of the Neanderthal genome has been published in the scientific journal Science together with a series of additional articles. The sequencing has been led by the genetic Svante Pääbo of the Max Planck Institute and, in fact, have only sequenced 60% of the Neanderthal genome. However, it is a great achievement, taking into account that the samples used were very deteriorated.

They have had to use a new technique to obtain information of such damaged samples. In addition, they have been especially careful with the contamination of other species. In fact, when the first draft of the Neanderthal genome was presented in 2006, some researchers demonstrated to be very contaminated with current human DNA (80%), and thanks to the technique they have now used they have managed to make the contamination of 0.6%.

In sequencing, samples of three bones found in a cave in Croatia were mainly used. They are of different individuals and the three of females. In addition, samples found in Russia, Germany and Spain (El Sidrón cave, Asturias) have been used.

The researchers have warned that the man of today and the Neanderthal have a great kinship and, therefore, it is possible that when comparing two specific areas of the genome, we will find more similarities between a Neanderthal and a current person than between the two current people.

Similarities and differences

To compare the Neanderthal genome with that of the current people, the Päääääääääbo group has decoded the genomes of five individuals of different origin: one South African, another West African, one Papuar, another Chinese and another French, respectively.

Thus, they have seen that there are more possibilities to find similarities between the Neanderthal genome and the genomes of people of non-African origin than with Africans. The simplest hypothesis is that the Neanderthals and ancestors of the current human being crossed after leaving Africa and before spreading through Eurasia. Specifically, it is estimated that the crossing took place between 100,000 and 50,000 years ago in Next Asia. The archaeological remains also show that at that time both populations lived there.

Researchers have found that between 1% and 4% of the current genome is Neanderthal. The population models show that when a colonizing population meets a stable, even if it is a small mixture, it can have a great reflection in the genome of the colonizers, if this colonizing population expands much. Thus, experts consider that hybridization was quite limited.

Only our own

On the other hand, the Päääbo team has developed a method to search for areas that, since the division of both species, are found in the genome of the current man and do not appear in the Neanderthal. These sequences are the result of a positive selection, so it is logical to think that they help advance the species.

This method has allowed to differentiate 212 zones, of which three genes have stood out. These genes, when mutated, affect mental and cognitive development. They are related to Down syndrome, schizophrenia, and autism. In addition, other genes have been found as a gene related to energy metabolism and another one related to the development of the skull, clavicle and chest.

In addition, the genome of the Neanderthal has been compared with other primates and, with the results of all comparisons, a catalogue of genetic characteristics that do not have the Neanderthals and other primates and that are characteristic of the current human being. Although it is still no more than a draft, researchers intend to complete and refine the catalogue, as it will serve to see what difference to people from the rest of organisms.