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April 20, 2004

Nature Wills It!

When I was in high school I was in a short-lived relationship with a girl from a Christian fundamentalist background. One day I asked her, "What if God decided to kill every man, woman and child on the face of the earth and blot them from existence, would that be 'good'?" Her answer was, "YES!" She wasn't a Christian philospher, and wasn't going to give me any complex refutation of the problem of evil, rather, she had in her mind a perfect identity between God and Good.

This sort of mind-set can be seen in some who argue that Nature dictates what is 'good,' a viewpoint that recently in the past century had grave consequences for the human race. I would advise caution to those who make these arguments, Nature does not by its essence take into account human conceptions of morality, nor does it dictate its affairs in a way most congenial to our proper ordering of things (that is, with the needs of logicians & moral philosophers in mind).

Where God(s) issue specific edicts from on high, Nature's laws are more inscrutable, and must be slowly and methodically teased out from the perceived chaos that surrounds us. Even when an injunction might seem straightforward, there is almost always a way to extract enough nuance to justify the converse position from what seems self-evident.

Let me illustrate: recently I think I have made it clear that the negative outcomes of consanguinity can echo throughout a society. Nevertheless, there is some evidence that the genetic load, the number of deleterious genes carried within a population, may be lower for Japanese than for American Caucasians [1], possibly as a consequence of the long term practice of cousin marriage in Japan (via negative selection against the higher frequency of recessive homozygotes). In such a fashion, one could argue that cousin marriage has a long term benefit that outweighs the short-term risks!

Now, I'm not going to make any sort of argument along those lines, but my main point is that just as religion has been used to justify almost any position under the heavens, Nature can be used to verify or refute any norm accessible to the verbal gymnastics of a sophist. Nature may act as the parameters which norms must take into account (a suggestion as to limitations or costs), but one must be not allow it to dictate what the norms themselves are.

[1] Consanguinity, Inbreeding, and Genetic Drift in Italy, page 17

(update from GC below)

GC Emeritus:

Here is the full text of the paper TJ Jones cited in comments, in pdf. Conclusion:

These results are also relevant to populations undergoing disturbance by humans. Inbreeding of formerly outbred populations occurs in many zoo populations, as well as domesticated populations and populations subjected to severe reductions in size as a result of human alterations of the environment. Extreme inbreeding has been recommended to purge genetic load and force the adaptation of endangered populations to the inbreeding regime they will experience under human management. This assumes that lowered fitness inevitably caused by increased homozygosity during this process will not be too severe or prolonged. The validity of this assumption depends on the severity and dominance of the mutant alleles in the population being inbred. Our results indicate that purging by the most severe inbreeding, self fertilization, could decrease fitness considerably with little recovery under inbreeding, and that fitness is restored only when the inbred lines are intercrossed.

Which is what I said initially. Now, one can come up with scenarios in which the selection is not solely focused against recessive homozygotes, in which case it will be considerably more efficacious (i.e. partial dominance situations where f(AA) != f(Aa) in the single locus case). But the time frame for elimination of recessives is very long if you've got complete dominance, and in the mean time you have to take the *massive* fitness hit of inbreeding depression.

Addendum from Razib: See, I told you there are problems relying on nature! Of course, that doesn't mean that I think biological arguments are worthless, rather, they offer a perspective on the costs that might be necessary if we aim toward a social "good."

Posted by razib at 12:57 AM