If you do not agree that psychological traits can be selected for, then it is you who do not understand genetics. There are many, many well documented examples of behaviors and psychological factors that are heritable. There is no reason to believe that some of those heritable factors could not influence what kinds of beliefs a person tends to form.
I am not saying there is one single gene responsible for scientific rationality, but there could easily be complex interactions of genes that influence what kinds of beliefs a person is more likely to be swayed by and hold. And it is clear from evolutionary theory that selective pressure increases some forms of behavior and decreases others, and behavior is clearly tied to beliefs in some fashion. For example, most people don't believe it's a good idea to kill their children right before they reach childbearing age. People who were more susceptible to those kinds of ideas are heavily selected against. Some people do murder their own children, but it is at the level of random mutations, less than about 1 in 500. Selective pressure can drive any trait down to that level, but not much below that level. (This is a broad generalization. Some negative traits can be driven down to about 1 in 2000 or even less, and some are as frequent as 1 in 250 if the genes involved are fragile and more prone to mutation.)
Initially, I made this argument partially as tongue in cheek. It is probably true that there is a correlation between belief in darwninism and a belief that abortion is acceptable, but in reality there are plenty of people who are against abortion yet do believe in darwinism (myself included).
In addition, there may be survival benefits of believing in Darwinism (although I would argue they would be very slight benefits, if any). It is hard to imagine there would be any significant survival advantage to being pro-abortion, however. You would have to believe that having abortions would eventually increase fecundity among the people who have abortions. I think that's a stretch, I would find it hard to believe. Perhaps there could be an advantage if a person was pro-abortion publically, but privately would never have an abortion. That way, they would be promoting the destruction of other people's genes while preserving their own. But I think this would be a very small minority of people who believe in abortion.
Anyway, from that point of view, I would say that my argument really applies more to abortion itself, since you could have selective pressures that just apply toward attitudes regarding abortions that do not affect attitudes about darwinism.
So let me amend it: Because people who believe in abortion are more likely to have abortions or encourage abortions by their offspring, and because even a tiny selective pressure (1% is enough) is sufficient to drive a trait down to near extinction (1 in a 500 or so), therefore abortion itself guarantees that more and more people will oppose abortion in successive generations. Any inherited psychological (or other) trait that tends to make people oppose abortion will be selected for.
We are only in about the second generation since Roe v. Wade, but already the polling trends clearly show more and more young people oppose abortion. Coincidence? Perhaps. We'll be more sure in another 2 or 3 generations. But the fact that many thousands of children of parents who believed in abortion failed to be born could certainly change the numbers, no?
Do you still believe my logic is twisted? Maybe before you accuse people of not understanding something, you should take into account that they could be so well-versed in the field and their understanding so surpasses your own that you do not even recognize the truth of it.
But with respect to a belief in evolution, I don't think abortion and evolution have the same genetic origin. And a belief in evolution is not a psychological trait unless you include general, rational thought as a psychological trait. To select against evolution would require selection against scientific rationality in general. You cannot reject one result of science selectively. Empirically, I've seen this in action. My co-workers, fellow scientists, who are ardent creationists, are also the worst for designing controlled experiments. Those who see evolution as scientifically valid are also the most skilled in experimental design and have advanced more than the creation absolutists. But if evolution, for whatever reason, offered the intellectually challeneged greater reporductive advantage, then future generations will become more intellectually challenged. The population will become more and more stupid and society will collectively forget why stupidity blossoms. Then, when greater intellect and rationality confir greater reproductive success, the balance will swing back.