Saturday, 18 November 2006

Who's Your Daddy?

Today's World Science revelations included Spider Monkeys having developed a natural perfume based on leaves (naturally used most often by the males); dark energy has been around for a long time and is causing the universe to expand at an increasingly fast rate; red wine is good; and new subatomic particles. I'll be focusing on the sequencing of Neanderthal DNA.

This is pretty cool stuff. Based on a Neanderthal thigh bone they have found a genetic similarity between us and them of 99.5%, although in many places they are more similar to chimpanzees than us. (By comparison humans and chimpanzees differ by 96%, and rats from mice by ten times that amount.) The DNA shows that the last time we had a common ancestor was 706,000 years ago, and that our DNA hasn't mixed for the last 330,000 years. (The last time chimps and us had a common ancestor was 6 million years ago.)

We, Homo sapiens, arrived in Europe between 40,000-50,000 years ago. Neanderthals disappeared completely between 33,000-24,000 years ago. And ever since then scientists have wondered why.

There's been two primary hypothesis. Firstly that we killed them off. This makes us somehow better adapted to the climate. We didn't necessarily have to kill them off through warfare- it could have been that we simply outcompeted them for space and food, though some studies indicate signs of violence on Neanderthal bones. Perhaps the change in climate at the time was one that Neanderthals were pre-conditioned to not be as adaptive to, but our Cro-Magnon ancestors were. If this is the case, then they are a separate species at the end, with no mixing between us, and should be called Homo neanderthalis.

The other option is that they disappeared through sex. Or rather, that they are still with us. We interbred with them to such an extent that their genes merged with us, and traces of Neanderthals still remain in modern humans. In which case they would be a subspecies, and properly called Homo sapiens neanderthalis. Of course, this wouldn't exclude the possibility of Homo sapiens sapiens (us) killing off large portions of them as well. And in either scenario, we once were of the same stock- the species concept is somewhat arbitrary, as it is always in a state of evolving flux. We can only say that if an animal can't, or doesn't, interbreed with another animal, it is of a different species. (Higher taxa are determined in a far more general manner, losing even this minimal definitiveness.)

This study indicates that the killing option was more likely. If the last time our genes were the same was 330,000 years ago, this was a long time after we diverged as modern humans, 130,000 years ago. Therefore we weren't around to interbreed with the Neanderthals at the time our DNA indicates similarities. However, other recent studies of the DNA of the very same bones indicate great similarites between the two lines, indicating continued sexual activity between the two groups.

The data is therefore still indeterminative at this point. However, the earlier study indicating sex between the two parties used a method that some say results in incomplete results mixed with intrusive DNA. This same analysis suggests that the difference between human and Neanderthal DNA will show to be less than that between the highly diverse African human populations. I'm personally rooting for the sex option, and I still have hope that it becomes the final conclusion. Probably a big part of this is my natural liberal bias- "Make love, not war" and all. Just a much more romantic notion to think that they disappeared that way, rather than us committing, however inadvertedly, the first and greatest mass genocide of our species. It doesn't help that the ones possibly committing this were my European ancestors.

But there are other reasons to hope for this. We know that Neanderthals had tools, cared for their injured, made art, abstract thinking, and probably buried their dead. This means something pretty far advanced. And however one determines the presence of the soul, life after death seems to be a big part of that, as it indicates the presence of a belief in the afterlife, and therefore some sort of religious belief.

Even more so, Neanderthal brain cases were larger than our own. They were also larger in body, and their brains were structured differently than ours- but there is the possibility that they were actually smarter. Solid evidence indeed that a bigger brain is not necessarily a selective advantage. I'd hate to lose out on all of that brain, culture, and heritage, wasted away, without a memory or a presence. Better to hope, however indefinite the evidence is at the moment, that there is a bit of Neanderthal in me, and you. Better to take the opportunity to glory in the compliment of intelligence, the next time somebody calls you a Neanderthal.

2 comments:

@bdul muHib said...

Joe said: Thanks for the update on Neanderthal DNA. I saw in the news that some DNA studies were done and was hoping to hear more about them.

Speaking of...(sort of)...while here in Nice, I visited a museum built around an archeological/paleontological site supposed to have been the remains of a 400,000 year old campsite (Cro-Magnon, I think). The site itself was a jumble (to the untrained eye) of rocks and fossils, but there were a bunch of really informative displays discussing how the site was dated, including sedimentology, pollen dating, radiometric dating, index fossils, etc.

Unfortunately, the displays were mostly in French and I did not have time to decipher them adequately. Nonetheless, it was quite detailed and convincing, and showed how much effort was put into dating just this one tiny site, and how concordant the results were, in contrast to some of the criticisms of such techniques given by some people we know.

@bdul muHib said...

I remember visiting some ruins in Jbail (Byblos), in Northern Lebanon. They went back 7,000 years. Not only was it amazing to be in a place where people lived 2,000 years before the Earth was created, there was also a huge sence of the numinous, to walk through ruins where children played, a scant 7,000 years ago, women baked bread, men exchanged goods (assuming a completely Patriarchal structure). It was with awe that I visited.

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