Neanderthal gene in modern human genome?
US American researchers speculate that the Neanderthals could have left traces in the genome of anatomically modern humans: A gene that controls brain growth is said to have spread among modern mankind. So far, however, there is no genetic evidence for this.
Last year, scientists led by the geneticist Bruce Lahn from the University of Chicago reported that a specific version of the gene Microcephalin (also called MCHP1) spread in the genome of Homo sapiens about 37,000 years ago. This version, haplogroup D, is found in seventy percent of humanity today [1].
Defects in this gene lead to microcephaly, a pathological disorder of brain growth. Conversely, the researchers assumed that microcephalin plays an important role in the large human brain.
Lahn and his colleagues have now taken a closer look at microcephalin haplogroup D. By comparing the genes of 89 individuals, they conclude that the variant arose 1.1 million years ago – long before Homo sapiens first appeared.
However, if the D version of the gene only appeared in anatomically modern humans 37,000 years ago, it must have been inherited from an archaic Homo lineage, Lahn argues. And since it mainly occurs in Europeans, the gene transfer probably took place in Europe. There is probably only one candidate for the carrier: Homo neanderthalensis, the Neanderthal [2].
Accordingly, the Neanderthals, who died out about 30,000 years ago, and anatomically modern humans must have had descendants together - an assumption that is extremely controversial among anthropologists. Gene comparisons between the two species - which would then have to be classified as subspecies - had so far not revealed any traces of a cross.
The American paleontologist Erik Trinkaus from Washington University in St. Louis – one of the most persistent proponents of the hybridization hypothesis – reported last week on 30,000-year-old Homo sapiens bones from Romania, and their anatomical features are partly typical for Neanderthals [3]. However, other researchers have questioned this interpretation.
Why the D version of the microcephalin gene should have prevailed in the Neanderthal - if he ever had it - also remains a mystery. In fact, the average brain volume of Neanderthals was slightly larger than that of modern humans - which does not allow any evidence of higher intelligence. The researchers around Lahn speculate that haplogroup D could have provided an adaptation advantage to the European Ice Age climate. But they don't know where this advantage lies.
Lahn emphasizes that his result does not provide clear evidence that the two human species crossed. He hopes to get clearer evidence when the Neanderthal genome has been completely deciphered – which could be the case in five to ten years. (aj)
