Why aliens don't look like us

Pharyngula wrote a great post yesterday on why it's silly to assume that aliens would be humanoid in appearance:

First, it isn't entirely crazy to argue for humanoids, and there's a perfectly good observed phenomenon that forms a rationale. It's called convergence. If you take organisms with initially similar body plans, and you put them in environments where there is selection for a particular function or a particular niche to fill, you'll sometimes see superficially similar solutions emerge . . . I would concede that if a primitive primate were to somehow colonize an alien world, and if that lineage gave rise to an intelligent tool-user, it would probably look vaguely humanoid, at least as much as the thylacine looks like a wolfoid. But here's the catch: with a different genetic stock, there are many different solutions to the same fundamental problem.

Read the whole thing.