I'm currently reading a really interesting book called Civilized life in the Universe. It details the thoughts on extraterrestrial life recorded by early astronomers.
For a modern scientist, it makes for strange reading, these assumptions that there must be life on the moon / mars etc. and the assumptions they made because of it. Herschel, famous for the discover of Uranus among many other things, was apparently so certain that there was life on the moon that he began classifying what we now know to be craters, as metropolis, city or village.
When thought about in the context of history these fairly large leaps of faith seem less ridiculous. 16th, 17th and even 18th Century astronomers can be thought of as living in the age of exploration. People got into boats, set off for the unknown and found new land masses. And when they got there, the land masses were populated. America, Australia, unknown worlds, but with populations.
Astronomers began to realise that there were planets and moons, which when looked through early telescopes, looked remarkably like earth. There were mountains, valleys and what looked like seas. Some of natures more excessive structures could easily be taken for architectural wonders. So it made sense that these worlds must be populated. If fact when put in the context of these belief systems it seems almost ridiculous that there wouldn't be life (not knowing about the atmospheric conditions we find on these planets)!
Although I haven't got to the end of the book it seems fairly clear that at some point the author is going to lay into SETI. We point radio telescopes at the stars in the belief that extra-terrestrial life will be just like us, another new land to find. But we do it while steeped in our own social/cultural and historical beliefs. In fact it is almost impossible not to.
Now, I'm not an astronomer and I don't know whether SETI will work or not, but its interesting to think about these issues in the context of some of the genetics discoveries that have come out recently. Phylogeography, the great neanderthal sex scandal to name a couple. Are these results clouded by our own assumptions and is it ever possible to over come them?
