marry marry quite contrary

I recently had drawn to my attention an article in the New Republic looking at the compatibility or otherwise of science, and more specifically the theory of evolution by natural selection, and religion. I'll be looking at that closely elsewhere, but meanwhile I want to take issue here with a more or less offhand remark made therein. Quoting the somewhat supine compatibilist language of the National Academy of Sciences, the author of the article, Jerry Coyne, writes this:

Would that it were that easy! True, there are religious scientists and Darwinian churchgoers. But this does not mean that faith and science are compatible, except in the trivial sense that both attitudes can be simultaneously embraced by a single human mind. (It is like saying that marriage and adultery are compatible because some married people are adulterers.)

The assumption here is that marriage and adultery are incompatible, but this is a false assumption. Of course, if you define marriage as a relation of complete loyalty, 'forsaking all others', then there may be something in the assumption, but that defines a particular ideal of marriage rather than the reality. A lot of married people commit adultery, with or without their partner's consent or knowledge. We must remember that marriage isn't a Christian institution, we must particularly remember this when governments try to argue, as ours has, that gay marriage shouldn't be allowed. Marriages have been undertaken for all sorts of reasons and in all sorts of circumstances; as tokens of commitment and love, for reasons of state, to legitimise children, to enhance resources, to spite others, to save relationships, to have a party, to experience what it's like to be married. There have been common law marriages, morganatic marriages, de facto marriages, arranged marriages, polygamous marriages, polyandrous marriages [unfortunately very rare these days], forced marriages, open marriages, walking marriages, same-sex marriages, handfast marriages and many more. In earlier times, when marriages were contracted between members of noble or royal families for political reasons, adultery was an implicit part of the bargain, which seems thoroughly reasonable where sexual attraction or love doesn't figure in the arrangement. I suspect that this sort of thing still happens in the modern world, more often than we'd like to admit.
If we simply equate marriage with monogamy, then we might think that adultery is counted out purely as a matter of logic, but recent research by ethologists has confounded many beliefs about avian and mammalian monogamy. It just doesn't happen as often, and isn't so tightly maintained as previously thought. It even seems to be the case that monogamy works best with a bit of something on the side from time to time. Where this leaves the human cultural practice of marrying is unclear, but it's certainly clear that the subject isn't so straightforward that it can be used in brackets to make a simple point in an argument.