Saturday, October 29, 2011

Cousin marriage: science, prejudice, and lifestyle mandates

Reposted from Freedom Democrats, 2009.

A perspective from PLoS Biology by Diane Paul and Hamish Spencer argues that there is no scientific basis for social stigma and laws against marriages of first cousins. The basic argument is that the risk of birth defects from first-cousin mating is negligible, and fear of such defects is the only basis for these attitudes and laws. This issue is interesting to libertarians as an illustration of how lawmakers often pretend that they are implementing the scientific management of society, when in fact their acts are based on nothing more than ignorant prejudice.

This issue is also interesting in how it connects with the evolution of our views towards government:

The laws must also be viewed in the context of a new, post–Civil War acceptance of the need for state oversight of education, commerce, and health and safety, including marriage and the family. Beginning in the 1860s, many states passed anti-miscegenation laws, increased the statutory age of marriage, and adopted or expanded medical and mental-capacity restrictions in marriage law. Thus, laws prohibiting cousin marriage were but one aspect of a more general trend to broaden state authority in areas previously considered private. And unlike the situation in Britain and much of Europe, cousin marriage in the US was associated not with the aristocracy and upper middle class but with much easier targets: immigrants and the rural poor.

One flaw in the argument from Paul and Spencer is that they emphasize the low costs of mating among cousins, but they ignore the low costs of prohibiting cousins from marrying--laws against cousin incest produce a negligible reduction in the pool of prospective spouses (as opposed to laws against same-sex marriage or inter-racial marriage, for example). I'm sure that this issue is terribly important for those few people who are romantically in love with their cousins, but it will never get onto the radar screen of anyone who is considering the total welfare of humanity, or the overall injustice in the world.

Paul and Spencer also largely ignore the social issues around cousin marriages. From modern American perspective, cousin marriages may disrupt the stability of the extended family. Conversely, in some societies, cousin-marriages seem to increase family stability and support--providing the child with benefits that may outweigh the risks of genetic problems (I'll link to the report if I can find it). We could also speculate that frequent cousin marriages may result in a more fragmented society with insular families: at its most extreme, it may facilitate the formation of cult-like social structures. Ultimately, I suspect that day-to-day social concerns play a much more direct role in policy formation than expert-mediated scientific knowledge.

A Google search reveals a fair amount of commentary on this issue. At, William Salaten notes that we will soon be able to genotype everyone to look for couples who carry identical alleles: if we embrace the logic of the prohibition on marriage of cousins, does that mean that genetic testing (a la GATTACA) should be a mandatory part of a marriage application, and the application be rejected if both individuals carry a potentially harmful recessive allele? Of course, as GATTACA illustrates, genetic selection on in vitro embryos is a solution to that problem.


anagory said...

1. When you say removing first cousins from the pool of eligible bachelor(ettes) reduces it by only a small percentage, you're reducing matters of the heart to a market transaction. Is nothing sacred? I'm not necessarily saying anything is, of course.

2. Do you seriously think that reducing policymaking to cost accounting is less arrogant than reducing it to science? I realize of course that your idea of the best policy is no policy, and your purpose here isn't about what's the right policy so much as what's the right set of priorities when it comes to dismantling policy.

It seems anti-authoritarians in general tend to classify marriage as a non-issue. I'm in accord with that. The state of the marriage institution today is the perfect example of why de-facto politics matters and de-jure politics does not.

Ricketson said...

Hi anagory, thanks for the comment. Your second point is the easier one to respond to, so I'll handle it first:

I think that scientific analysis is part of cost-accounting, not that they are separate. My motivation for publicizing Paul and Spencer's essay was to attack the ideology of technocratic liberalism by showing that the claim of scientific expertise is hogwash.

Aside from that, I was just pointing out why their argument would not be convincing to the utilitarians whom they seem to be addressing (as you noted, the "inbreeding" argument wouldn't be persuasive to a libertarian under any circumstance). Finally, as you recognized, there is the need to decide where to expend our efforts, and cousin-marriage does not seem to be the most pressing issue.

As for the first point (that I am discussing love as though it is a market transaction), I think that there is only the slightest similarity between the two. In fact, I think that I'm just being realistic about the process of finding a spouse, and this has very little to do with markets. I am only acknowledging that we are intelligent, physical beings (with all that implies); if that is equal to saying that "love is a market transaction", then the word "market" has no meaning (since it would apply to all human goal-oriented behaviors).

More to the point, I think that there are many goods in the world, and attaining these goods requires both a particular sequences of events (contingencies) and an allocation of resources. If we fail to obtain a good due to contingencies, then it frees up those resources for allocation to another good. Regarding marriage, if we fail to establish a family with one person, then we will be able to establish a family with another person.

I don't see any "market" behavior in that line of reasoning, even if markets are based on similar behavior by individuals. To have markets, you not only need to have goal-oriented agents, you need to have multiple agents exchanging goods, where these agents are bargaining based on their perception of alternative exchange opportunities offered by third parties. While this may occur to some extent in the process of finding a spouse, I did not discuss it here. I do discuss it a little in the subsequent post. To the extent that there some market-type dynamic occurring during spouse selection (particularly at the earliest stages of dating), I don't think that it makes dating into a market, nor does it necessarily make the spousal relationship crass or make the process of falling-in-love profane.