Saturday, February 14, 2009

No Hanky-Panky?

My sister referenced an article on the BBC website, detailing the latest news in the mapping of the Neanderthal DNA sequence. Scientists are about 60% complete in mapping the Neanderthal genome, and so far have found 'no evidence' of interbreeding with modern humans. This does not mean that hanky-panky did not happen (just think of the way modern men act, then cast your mind back to 50,000 years ago), it just means that any gene exchange had an negligible effect on the modern human DNA sequence. There is still controversy on this point.

A couple of other interesting facts about the Neanderthal genome have surfaced. One, our burly friends probably possessed the ability for speech and language, a marvel which we have only credited to Cro-Magnons. Neanderthals have the FOXP2 gene, which is associated with speech and language in modern humans. Chimpanzees do not have this gene. Scientists point out though that other genes are associated with the complex ability for speech and language. The Neanderthals may not have had those genes, so the 'quality' of their speech is unknown. Were there no future Shakespeares among them, as there were in the Cro-Magnon?

We know the Neanderthals shared 99.5 to 99.9% of our gene sequence. Therefore it is important to examine how our gene sequence is different from Neanderthals as well as how it is the same. If not the ability for language, is there any other quality that made this relatively small group of Cro-Magnons migrating from Northern Africa 100,000 years ago destined to rule the planet? Was it just plain luck, or is the answer in our genes?

One gene causing much controversy is the Microcephalin gene, a gene related to brain size and development. This gene is very pronounced in modern humans now (70%). Controversy has ensued because the gene variant is more common among European and Asian populations than Africans. People are disturbed by erroneous assumptions that may be drawn by this information, as studies have included only small samples of modern humans.

In more archaic human populations, the modern form of the gene emerged in Eurasians and not Sub-Saharan African populations. Some have raised the possibly that the gene resulted from an admixture between Neanderthals (or other primitive Homo-Erectus humans in Asia) and modern humans. What's also interesting about this gene is it emerged around 37,000 years ago, right around the time of Neanderthal and Cro-Magnon co-existence. The rapid raise of the gene's distribution suggests a sudden introduction of an element (mutation, environmental factor, other human population) that was not present earlier.

However, the Neanderthals currently being studied and mapped
do not show the presence of the modern Microcephalin gene, but the more primitive form of the Microcephalin gene (shared by Sub-Saharan Africans) . Thus the admixture theory so far does not hold water.

The other possibly is that the gene was established in the modern human population prior to exiting Africa, and this is the 'special quality' that allowed our dominance and eventual replacement of all other humans. Or, the gene evolved in modern humans during the time of interaction with Neanderthals, but was not contributed by them.

1 comment:

Captain Kulig said...

it's just ALL about continental drift and divide!