Everyone knows how it goes in Star Trek; the intrepid team with at least Captain Kirk, a varying number of people and one guy in a red shirt go on to a new planet; the red shirt dies in some attack or another and Kirk goes off and boinks some hot alien lady. There are several things to consider about alien life however and before I go on, I’d like to recommend the talk given by Professor PZ Myers (he teaches evolutionary biology at the University of Minnesota) at this year’s TAM; A Skeptical Look at Aliens
(Part 2 , Part 3. You should also take a gander at the two slides he left out because he ran out of time)
Professor Myers makes an excellent point about how diverse life is even on this planet. How different might it be on another planet?
Last year there was that whole controversy about the arsenic-loving bacteria, and while they were cool and everything, they’re not actually necessary for life outside of our own Tellus to exist. We are made, literally, out of stardust and not only that but we are also made of the most common elements in the whole universe, in roughly the relative amounts that they occur in the universe. While it seems like other planets in our solar system may not have developed life, they’re still likely to contain roughly the same elements in roughly the same quantities as Earth does. Less Oxygen of course, since it’s a by-product of photosynthesis. There are some speculations that Mars may have had life at some point before its atmosphere was blown away by solar winds. Strike that. There are some speculations that Mars may still contain life underneath the crust, hidden in the ice that may or may not be hidden there.
On Earth it would seem that DNA has only developed once. For life to evolve it is absolutely necessary for DNA or something similar to develop first. Life depends completely on a self-replicating mechanism. Evolution depends on that mechanism being flawed. Let me make it clear that I’m not saying that evolution is impossible or purely happened by chance or other such creationist nonsense. The copying mechanism itself is ever so slightly flawed in that it won’t produce the same exact copy every time. It’s like those episodes of Catch-That-Murderer type of shows (CSI, NCIS, Criminal Minds, etc) where the killer is caught by his copier or printer. The two papers look exactly the same, but the killer’s copy has a flaw that’s only noticeable when you look at it with a magnifying glass or microscope. Of course, when we get into sexual reproduction the importance of mutation becomes much less pronounced since any offspring will inevitably be a combination of both parents’ genes and so different from both.
Let’s be honest; ape-like intelligent extra-terrestials seem very unlikely to say the least. As far as we know, our type of imaginative intelligence has developed only once on this planet. To compare, echo-location has apparently evolved several times, independent of each other. Eyes are also ubiquitous in this sense, having evolved several times and in several ways. Although, to be fair, we’re not nacessarily up to speed on other species intelligence either. We know that there are other self-aware at least moderately intelligent species on earth (dolphins, some molluscs, some other big apes and some birds). So who knows, there may be intelligent life on Earth as well.