Your Neandertal Ancestors

Scientific convention used to be that modern humans came out of Africa and completely replaced Neandertals (also spelled "Neanderthals") without interbreeding (for example, see here). New evidence suggests that this hypothesis is incorrect, according to an article by Ann Gibbons called "Close Encounters of the Prehistoric Kind." The article appears in the May 7, 2010 edition of Science (available online only to subscribers). An international team has now completed the draft sequence of the Neandertal genome, which includes more than 3 billion nucleotides collected from the bones of three female Neandertals who lived in Croatia more than 38,000 years ago." The analysis described was astoundingly complex, and the consequences of this analysis are startling:

By comparing this composite Neandertal genome with the complete genomes of five living humans from different parts of the world, researchers found that both Europeans and Asians share 1% to 4% of their nuclear DNA with Neandertals. But Africans do not. This suggests that early modern humans interbred with Neandertals after moderns left Africa, but before they spread into Asia and Europe. The evidence showing interbreeding is "incontrovertible," says paleoanthropologist John Hawks of the University of Wisconsin, Madison, who was not involved in the work. "There's no other way you can explain this."

Therefore, many people living outside of Africa carry "a small but significant amount of DNA from these extinct humans." The consequences of this amazing finding are not lost on anyone:

In a sense, the Neandertals are then not altogether extinct, says lead author Svante Paabo, a paleogeneticist at the Max Planck Institute for evolutionary anthropology in Leipzig Germany, who is surprised to find out he was part Neanderthal. "They live on in some of us."

The Science article presents the following list of things we now know about Neanderthals:
  • The genomes of modern humans and Neanderthals are 99.84% identical.
  • The scientific data don't support interbreeding when scientists had most expected it (between 45,000 and 30,000 years ago in Europe).
  • Neanderthals coexisted with modern humans in Europe from 30,000 to 45,000 years ago, and perhaps in the Middle East as early as 80,000 years ago.
  • The amount of admixture is tiny, even among Europeans and Asians, but Neanderthals "are significantly more closely related to non-Africans than Africans on average.
  • The new data fits with the discovery of fossils and stone tools from Israel caves about 80,000 years ago (modern humans and Neanderthals both used these caves and had much in common--they used similar tool-kits and under the same animals). One Neandertal skeleton from the Middle East looked "less robust than Neanderthals in Asia and Europe.
  • Despite the ability to sequence some Neanderthal DNA, there is no possibility of cloning a Neanderthal.
  • "The isolated DNA was in pieces typically about 50 bases long, and there were many missing stretches. Further, despite the story one often hears in the mass media, DNA is not completely responsible for the appearance of an animal. "Chemical modifications to the genome, the way chromosomes arrange in the nucleus, and maternal components in the egg all play a role in translating a genetic blueprint into a viable individual." None of these are available with regard to Neanderthals. As soon as you substitute another oocyte (e.g., that of a modern human) for that of a Neandertal, you would change the resulting organism.
Despite the fact that there was some interbreeding, it did not happen much. This article quotes evolutionary geneticist Sarah Tishkoff, who asked "Was it a cultural barrier?" We are cousins with every living thing on planet Earth (including trees and see here), but many of us are both cousins and descendants of Neandertals. Therefore, for those of you who have had ancestors from anywhere outside of Africa (keeping in mind that all of us have ancestors from Africa), you are African and you are Neandertal. I'm planning on having a bit of fun the next time a bureaucratic form requires me to designate my "race."

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The wheel of life turns in the backyard

My family has a dog named "Holly." She's a friendly mutt. Loyal to a fault. A big raccoon took up residence on or in our garage recently, and Holly didn't like it at all. Our neighbors often saw the raccoon on our garage roof. We often heard Holly's barking, thanks to the raccoon. We live in the middle of the City of St. Louis, and we know that there are lots of raccoons running around. The City Animal Control told me that if we trapped a raccoon, they would come by to pick it up. By the time I got around to setting a trap, the neighbors mentioned that there was now one big raccoon and several small ones. As I was setting the trap near the garage, I could smell the smell of death. Even as we were trying to trap a raccoon, at least one of the raccoons had already died. I really do wonder how they can survive in a congested urban area, but the do, often enough, anyway. The next morning, my children excitedly mentioned that we had caught a large raccoon in our trap. raccoonIt looked like it weighed 15 pounds. I called the City Animal Control, and they indicated that they would come out and take away the raccoon. I didn't ask where they would take it, as I assumed that I was essentially dooming the mother raccoon to death, and possibly dooming the babies too (by taking away their mother). As I mentioned above, even as we waited for Animal Control, we were smelling the smell of death whenever we were in our garage. It was getting stronger by the hour. The next day (today), we still couldn't find any dead raccoon baby, but we did find that there were flies all over the garage, so the raccoon body was apparently nearby. window-fliesNature, red in tooth and claw. But I'm not done yet. This mini-life cycle started with a human family who wanted the companionship of a neotonous wolf (Holly), who got upset at the raccoon, who had been deprived of her natural habitat by the humans. At least one of her dead babies was being eaten by flies. Now what about the flies? You've all heard the joke, "Why did the fly fly?" Answer: "Because the spider spider." This afternoon that joke became incarnate, right in the corner of my garage. Though these macro photos didn't turn out in the sharpest focus, you can clearly see that a spider had caught one of the flies in a web and was making a meal of it (there's also a piece of leaf in the foreground). image by Erich Vieth If only we humans ate spiders, this cycle would be at its end (or a beginning), but it gets all the more convoluted from here. For instance, 90% of the cells in your body are "aliens," most of them are bacteria that allow us to digest our food. Without them we would die. And while I'm pointing out connections, consider that parallel universe of fungi living under the ground. Two weeks ago, I saw an eruption of mushroom (their fruiting bodies) in the front yard. Without this fungi, most of our plants would die. img_6679 It occurred to me today that, right here in the middle of a major city, whether or not I'm aware of it, nature is churning away, doing its thing in an entirely amoral way. Except for us humans, they say. We supposedly have a "moral" sense that is not anchored to our animal-ness. Or are we spinning elaborate intellectual webs in coming to this conclusion?

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