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alexflint comments on Simon Conway Morris: "Aliens are likely to look and behave like us". - Less Wrong
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His argument is based on the idea that organisms evolve to fill some niche in an ecosystem, and that different ecosystems may develop niches that require similar characteristics. E.g. a "carnivore" niche may call for organisms with sharp teeth, fast movements, etc, and we should be unsurprised when we find that independently evolved carnivores on different continents on Earth all exhibit these same characteristics. He points out examples of independently evolved organisms that have ended up very similar due to this phenomenon (I think sabre tooth tigers and a particular ecosystem of rainforrest frogs were among his examples).
Morris posits humans as filling the "intelligent" niche, which he would claim requires many of the characteristics we exhibit, so he would say that if we "ran evolution a second time" then we may again end up with intelligent bipedal creatures not unlike humans.
the "sharp teeth" assumption is a silly one, because it requires evolution of earth-like mouths, digestive systems, etc. There is no reason whatsoever to assume evolution would take this course in two independent "trials."
Perhaps so, but I guess Simon Conway Morris would disagree here. He might point out the independent evolution of the camera eye in multiple phyla, or any of these: http://en.wikipedia.org/wiki/List_of_examples_of_convergent_evolution. His view is certainly an extreme one but it's backed up by extensive evidence and shouldn't be dismissed off-hand.
that list is broken, but I take your point.
However, I'm not sure how relevant it is. Covergent evolution is quite rare, when you consider all of evolutionary history. The last common ancestor of cephalopod and vertebrates (camera eye) was 750 mya and had a distinct photorecevier. A recent studies have shown a 70% similarity in the gene expression profile between octopus and human eye tissue. This suggests that they are not so convergent as commonly thought. (source: http://stke.sciencemag.org/cgi/content/full/sci;313/5795/1914)
Simmons suggest that convergent evolution, is not only possible but likely, by tacking on an extra almost 3 Billion years to this time scale? I doubt that our genetic material and/or cell structure would even be the same, given this amount of time.
Sounds like someone needs to check their priors.