While reading an internet forum (the closest thing to the fiction we call hell) recently, one dedicated to atheism, a commenter decided to explode about his particular (mis)understanding of infidels in general. His straw man paints infidels as inexplicably interested in pop-sci presentations of "evolution" (read: evolutionary biology) and cosmology, inter alia. From this, I surmise that there might be some lack of understanding in the theist (or rather, anti-infidel) community about why so many atheists are interested in pop-science renderings of evolutionary biology (e.g. Richard Dawkins's fine The Greatest Show on Earth or Jerry Coyne's excellent Why Evolution is True, among other titles) and, to a lesser extent, cosmology.
The big answer is relevance!
Perhaps it is the case that theists are too busy making anti-evolution arguments or trying to use those to shoehorn creationism back into public schools in the United States to have noticed, but a lot of religious folks these days seem to like to argue on the behalf of their God by trying to disparage evolutionary biology. This is a bit funny, in that simultaneously disheartening kind of way, because disproving evolution wouldn't provide a drop of evidence for the existence of their almost surely imaginary God and is thus an endeavor without point--though not without consequences. Sick of it up to their eyeballs, mostly because of those consequences, infidels often feel compelled to brush up on their evolutionary biology, perhaps to fight the good fight with their faith-filled and uninformed neighbors and perhaps only to satisfy their own curiosities about the actually viable explanation for where we come from. Believe it or not, the question is actually more interesting when you get rid of "God did it!" as a pseudo-explanation.
This leads me to a second big reason: it's interesting. Our origins are fascinating. For those of us who are already familiar with evolutionary biology, we already know why. For those who are ignorant of the subject and curious, it's worth the read. For those of you who are obstinately opposed, honestly, you don't know what you're missing. Your non-explanation lacks in every conceivable way to what evolutionary biology is telling us. Incidentally, evolutionary biology is right here too, regardless of your beliefs, so if you resist it, you persist in being wrong--again, with pretty big consequences since this willful misunderstanding is so widespread.
Connected to that reason is the one that is going to separate the evolutionary biology from the cosmology here: tractability. Biology is a lovely science. It sits right at a cusp of academic efforts--challenging as it may be, biology rests rather at the tipping point between hard and soft sciences (this being defined in the amount of mathematical "hardness" they require). This makes biology, including evolutionary biology, a very approachable subject for a lay reader, presuming a good lay presentation of it. Cosmology, rather unfortunately, because it formally resides locked away somewhere beyond differential geometry and tensor calculus tends to lose some folks at times where biology connects a little more easily, however great the lay renditions of cosmological ideas happen to be (one thinks of Hawking and Krauss here, at the least). Cosmology, in quite the formal sense, is too hard for the kind of mass appeal that biology can command, particularly since it doesn't actually specialize in the kinds of pretty pictures that astronomy does.
There's another huge reason why evolutionary biology is hot with infidels, and it happens to be the one that keeps cosmology in the picture, even though the latter is so hard: it's about us. As it turns out theists aren't the only ones guilty of indulging in anthropocentrism, and these sciences that concern our ultimate origins therefore possess a visceral appeal for the scientifically literate and curious. That's pretty huge, actually, particularly when one spends enough time with these ideas to see how much patently better they do than creationist appeals (which are usually to ignorance and tradition).
There's actually another reason that's worth mentioning: it's still pretty new news, at least for a lot of us. Having been raised in the South, my high school biology classes were careful to stay away from the (religiously manufactured) controversy surrounding the teaching of evolution, and so these books that are written at the high school and collegiate level are a real treat for those of us who are filling in gaps in our high school educations that shouldn't have ever been there.
Oh, yeah, and because these subjects are genuinely interesting is another big reason.
Importantly, though, infidels are often fascinated by these topics, but they are also often not interested in them beyond a passing glance. A great many infidels are comparably scientifically illiterate and ignorant as are the theists trying to shoot down evolutionary biology (they usually can't do much with cosmology except to appeal to stupid philosophical arguments that the science has utterly dethroned). They also aren't typically part of the problem, referencing those huge consequences I've mentioned a couple of times. Still, I only mention this point because the caricature of the infidel as an angry, condescending, biology-lover is at least false in the last bit (and usually in the entirety). One doesn't have to understand scientific theories to reject claims about the reality of Santa Claus, and it is likewise with God.
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