|MadSci Network: Genetics|
Hi Clay, You ask a rather interesting question, and one which I must admit we haven't much data to address. However, part of the fun of science is speculating on the possibilities in light of current knowledge. So here goes... I'm interpreting your basic thesis as "Humans aren't particularly well adapted to our current ecological niche, whereas other animals seem well adapted to their niches. Therefore it is possible that these maladaptations came from aliens." I'm not sure if you're familiar with Occam's Razor. It's a simple little rule that states that the simplest answer is usually correct. So let's see if there might be a simple answer for why humans are so badly adapted which relies on biological rules where we have strong evidence, as opposed to aliens, where the evidence is pretty flimsy. First I want to examine the premise that humans are poorly adapted to the environment. Although a naked human being doesn't really stand much of a chance anywhere in the world, we have occupied virtually every environment available, from the islands of Polynesia to the mountains of the Himalayas, from the deserts of the Middle East to the jungles of Central America. How could a poorly adapted animal succeed in so many environments? The answer is that human adaptation long ago made the leap from genetics to culture. For example, it's a lot easier (and faster) to learn to wear pelts than to grow hair all over. Same goes for learning to make spears vs. growing fangs. I'm just trying to point out that it doesn't make sense to look at how well humans are adapted to the environment without looking at our tools, and from this standpoint we are tremendously well adapted to the world. Of course, this does come with a caveat. Lower back pain (and difficult child birth, for that matter) do indeed represent maladaptations to walking upright. There's a lot of debate at the moment about why we started walking upright in the first place, whether it was a cause or a consequence of tool use or envirnmental change. The important part is that it was a relatively recent adaptation compared to most other traits (grasping hands, color eyesight, etc.) and therefore the kinks haven't entirely been worked out yet. Given the size of the current human population and the pace of technological adaptation, it's pretty likely that genetic evolution as we knew it is over for the human species. We're much less likely to evolve to survive the modern diet than we are to find ways to produce a healthy Twinkie. Returning to your original question, the DNA of every human is 99.9% identical to every other human, regardless of race. Perhaps more surprising is that human DNA is 98 to 99% identical to chimps. Based on the fossil record this is a reasonable divergence, and can be explained as a simple consequence of time and the mutation rate of DNA. So using Occam's Razor, because we can explain human adaptation using simple systems we know a lot about (mutation, evolution, and cultural adaptation), alien DNA is pretty unlikely. I know this may be a bit disappointing to X-Files fans, but I long ago gave up hope that their writers would try to keep the science in their science fiction in the realm of the possible, much less the plausible. Chris
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