The mystery of the chromosome that separated us from the Neanderthals – BBC World

Image copyright S. ENTRESSANGLEE. DAYNESSCIENCE PHOTO LIBRARY

Image caption Missed in time the Y chromosome Neanderthal or simply was not compatible with our immune system?

It is a well known fact that many modern humans carry in their genetic code up to 4% of the DNA of Neanderthals.

But an international study, led by the School of Medicine at Stanford University (USA), has just revealed that the Y chromosome neandertal -the genetic package is passed to children- is not present in modern populations.

“We found the Y chromosome neandertal in any of the samples tested” , the scientist said Peruvian Carlos Bustamante, co-author of the research.

“that does not prove that the chromosome has been completely extinguished, but it probably is,” added Bustamante.

the study was published in American Journal of Human Genetics (American Journal of Human Genetics).

enigmatic Mestizaje

Our ancestors and Neanderthals they passed approximately 50,000 years ago, after the Homo sapiens leave his native Africa and began to colonize Eurasia.

and there is still a small amount of DNA in our genes that is the legacy of that miscegenation.

Image copyright Getty

Image caption The crossing between Homo sapiens and Neanderthals occurred more than 50,000 years ago.

But the new analysis reveals that the Y chromosome Neanderthal is completely different from that of modern humans.

the Y chromosome Neanderthals may have played a role in mating ancient humans and Neanderthals

Carlos Bustamante, co-author

the researchers say it is possible that chromosome initially circulated in the genetic code of modern humans, but lost, random, over the millennia .

Another possibility is that genes that chromosome were incompatible with other genes of Homo sapiens .

And, in fact, scientists found evidence that support the latter theory.

genetic Incompatibilities

Image copyright Thinkstock

Image caption Y chromosomes Neanderthals are specific to men.

Some of the Y chromosome genes of Neanderthals are part of the immune system .

Three of them are “minor histocompatibility antigens” or HY genes which resemble those that transplant surgeons checked to ensure that donors and organ recipients have immune profiles similar.

in addition, these genes Neanderthals found on the Y chromosome are specific to men.

in theory, the immune system of women can attack a male fetus that has some of these Neanderthals genes .

And if miscarriages of babies carrying these chromosomes are produced consistently, that would explain its absence in the genetic code of modern humans.

so far so are only hypotheses, but it is known that the immune system of women today may react negatively to the male offspring if there is genetic incompatibility.

“the functional nature of the mutations that we found suggests that sequences the Y chromosome neandertal they might have played a role in mating ancient humans and Neanderthals “expicó Bustamante.

” we need to do more experiments to prove it and we’re working on it ” added the scientist.

But, for now, the mystery will remain unsolved.