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April 14, 2005

Empirical flesh on logical bones

R.A. Fisher, the geneticist and statistician who gave us the greater portion of the theoretical basis for the "Neo-Darwinian Modern Synthesis,"1 was an ardent eugenicist who applied evolutionary principles to his understanding of history. Fisher explored the human past on his spare time through readings of the great scholars of his time, Gibbon and Frazier for example, and attempted to extract from it empirical lessons that he applied in a genetical context. Reading R.A. Fisher: the Life of a Scientist I came across his thesis that infanticidal cultures by their nature are doomed to extinction. He even expressed this opinion in front of a group of eugenicists who were favorable toward contraception, an audience that included Margaret Sanger, the founder of Planned Parenthood.2 The logic is sensible: those who are predisposed to procreate are the ones who have descendents, and Fisher obviously assumed that the ideological disposition toward pro-natalism had some heritable component. Assuming a few basic facts it is difficult to argue with the chain of propositions.

But here is where the problem comes in. From what I can gather Fisher believed that these selection pressures drove cultural change. He seemed to hold that the anti-natal pagan European culture gave way to Christianity because of the latter's positive view of fecundity, and attributed the rise of Islam partly to the anti-infanticide jeremiads of Muhammed. My first reaction was that this is historically implausible.

My rationale is this: while selection happens gradually over a few generations (unless you have a sweep induced by a super-plague), the shift toward pro-natalism as a matter of ideology occurred rather quickly. In the case of Christianity its victory over paganism occurred in the 4th century (at least in the Roman Empire), while Islam banished infanticide in one generation. This does not seem to jive well with a Fisherian gradualist model, unless one assumes radical fitness differentials or an incredible amount of heritable variation on the point of natalist sympathies (both of which I find implausible).

Of course an immediate critique is that a "critical mass," or threshold, was reached at which point the culture "flipped" into another mode. Cultural mores can change far more quickly than genetical predispositions. Once the cultural value changed one would assume that the fitness differential decreased as the Church and State now was on the side of abandoned infants and punished parents who attempted to discard them.

But there is another layer to this issue, there is often a difference between ideology and practice. Unlike the pagan Gauls the Roman Catholic French of the 18th century opposed infanticide on principle. But in reality the mortality rates were in excess of 90% before the age of five for many of the "foundling" orphanages where parents who could not or would not raise their infants abdicated their responsibility. Though de jure there was no infanticide, the reality is that the morality rate for these foundlings was so high that the reproductive difference attributable solely to the abolishment of infanticide might have been minimal. Additionally, many individuals married extremely late or remained unmarried.

My point is that all the contentions above are "true" to some extent. Fisher's genetical logic is clear. The pro-natalist ideology of early Christianity and Islam in contrast to the more ambivalent attitude of the pagans is also textually attributed. Scholars who study the rates of pre-modern adoption and abandonment also find that the de facto difference between cultures that exist in the same environment3 but espouse different ideologies is far less than one would gather from the official textual sources which address the point specifically. Just because one aspect of an argument is logically or empirically supported does not mean that it is prima facie the "correct" position. One must keep digging and exploring for soft spots, and try and see if it looks the same from another angle. This seems like an obvious point, but there is a problem with all sorts of scholars getting carried away with their own particular methodological paradigm and draining nuance from their paintings of the past and present. Economists live in a world of rational choice & the invisible hand, evolutionists see natural selection at work replicating its magic via its universal algorithm, while anthropologists conceive of a flux competing cultures. All of these answers are slices of the truth. Undernearth the various trends in history there is the reality that those who procreate inherit the future genetically. Nevertheless, how culture works upon these genetic changes and how evolution feeds back into culture can be a very complicated affair. We can't blame Fisher too much for his naiveté, he lived in an age where scholars were still asserting big bold ultimate answers based on some rather meager sources. But we don't have the same excuse.

1 - Others would include Wright, Mayr, Dobzhansky, Huxley, Simpson and Haldane.

2 - Though concerned about the procreation of the "lower orders" my impression from the reading so far is that Fisher was more focused on "positive eugenics" than "negative eugenics" in the day to day world. That is, he wanted the "fit" to reproduce and spent less time considering how the "unfit" shouldn't. He himself had 8 children.

3 - I would argue that pro-natalism and anti-natalism is far more clear when it comes to different lifestyles, for example, the Bantu of Bostwana vs. the Khoisan. While the former are pro-natalist farmers the latter are anti-natalist hunter-gatherers. An elucidated ideology is unnecessary when the realities of life and its needs dictate the pattern of behavior.

Posted by razib at 05:35 PM