William Saletan at Slate.com argues that we need to rethink laws against marrying within the family:

Does science support our laws against incest and cousin marriage? If so, does it also support other laws that would restrict sexual or procreative freedom in the name of genetic health?

To longtime readers of Human Nature, this question should be, if you\’ll pardon the term, familiar. A few years ago, we looked at the science and ethics of \”The Love That Dare Not Speak Its Surname.\” Then we examined the prevalence of inbreeding in nature. Then we considered the awkward question of why, if incest is too genetically risky to permit, maternity in your 40s isn\’t.

He goes on to cite statistics that show very low birth abnormality rates in cultures where marrying relatives is common, in an attempt to convince us that laws prohibiting such activity are overly restrictive.

I actually appreciate arguments like these that challenge conventional wisdom with facts.  Yet, in this case, I can\’t go along with the thesis.  Facts or no facts, inter-family sex should remain illegal for one important, time-tested reason: