Monday, April 30, 2007

Adaptive? Aye!

In Chapter Five of 'The God Delusion' Richard considers the origin of religion, and briefly considers the possibility that it might be adaptive before moving on to his own theory. Richard is dismissive of group selection theories, as I said before. In fact, for reasons that I don’t quite understand, the idea of group selection in general seems to be anathematised by the evolutionary biology community. Perhaps this is a reaction against the pernicious ideas of the 19th and 20th centuries that saw human history in terms of the struggle between different races

Richard takes only one possible example of group selection for religion, a tribe with a ‘God of battles’ that impels it to war against other tribes and squish them like bugs. He outlines how this could happen, then says:

‘Those of us who belittle group selection admit that in principle it can happen.
The question is whether it amounts to a significant force in evolution. When it
is pitted against selection at lower levels - as when group selection is
advanced as an explanation for individual self-sacrifice- lower-level selection
is likely to be stronger. In our hypothetical tribe, imagine a single
self-interested warrior in an army dominated by aspiring martyrs eager to die
for the tribe and earn a heavenly reward. He will be only slightly less likely
to end up on the winning side as a result of hanging back in the battle to save
his own skin. The martyrdom of his comrades will benefit him more than it
benefits each one of them on average, because they wull be dead. He is more
likely to reproduce than theyt are, and his genes for refusing to be marrtyred
are more likely to be reproduced into the next generation. Hence tendencies
towards martyrdom will decline in future generations.'

Richard undercuts his own argument when he decries (in Chapter 7) the appalling behaviour of the Israelites as they entered the land of Canaan, described with approval in the Old Testament:

The book of Numbers tells how God incited Moses to attack the Midianites. His
army made short work of slaying all the men, and they burned all the Midianite
cities, but they didn’t kill the women and children. This merciful restraint by
his soldiers infuriated Moses, and he gave orders that all the boy children
should be killed, and all the women who were not virgins.

Where are the Midianites today? Where are the Amalekites? Where are the Jebusites? The Israelites are still there. In these sort of ‘nature red in tooth and claw’ examples, it is not what happens to the winners that is most important, but what happens to the losers. They don’t pass on their genes at all.

But ‘nature red in tooth and claw’ is, as Richard knows, a classic misrepresentation of what evolution is all about, and the ‘God of battles’ has precious little to do with the adaptive significance of religion. Evolution is all about outbreeding the competition. Remember those Israelites that are still there? There are more religious Jews today as a proportion of the Western Jewish population than there were fifty years ago. Not because they have conquered the secular Jews, but because they have consistently had more children.

You can snicker all you like at my tribe for spending all its time building grandiose religious monuments and making yak butter to burn in our temples, but if we have 2.2 children survive to adulthood on average and your more gainfully employed tribe only have 1.9, in a few hundred years you will be history and we will still be around. At the end of 2005 I read a letter to the editor in the Devil Bunny City Morning Herald making the ridiculous suggestion that certain religions were bad from an evolutionary point of view because they encouraged people to have more offspring than the environment could support. This is the opposite of the truth. As long as there is a decent chance that some of your offspring can leave your overpopulated homeland to spread their genes and memes elsewhere, this is an excellent strategy.

At the business end of evolution- outbreeding the competition- religion is becoming more adaptive, not less, with the spread of contraception.

A more specific example of the adaptive significance of religion can be seen in the response of Sub-Saharan Africa to the AIDS pandemic. I sarted collecting data on this part of the world from the CIA world factbook about a decade ago, on the theory that people to some extent practice what they preach and that the spread of AIDS should favour monotheist religions that place a premium on fidelity in marriage, specifically Islam. Though a lot of the data on religious affiliation in Africa seem to be extremely rubbery and numbers are doubtless manipulated for political reasons, the overall proportion of Muslims has risen from 32.9 to 34.1% in Sub Saharan Africa as a whole in the years 1989-2005. In Kenya, for instance, the proportion of Muslims rose from 6% to 10% in that time, and much larger gains are claimed for Sierra Leone (30% to 45%), Togo (10% to 20%), the Ivory Coast (25% to 35-40%) and Burkina Faso (25% to 50%!). Those countries where the proportion of Muslims has apparently declined are only a few where a large hand-waving estimate has evidently been exchanged for a more precise one: significantly Malawi (20% to 12.8%) and Ghana (30% to 15.6%). More importantly, since all those numbers may have been influenced by all sorts of other factors, is that most individual non-Muslim countries have seen a much sharper decline in population growth rate than most individual Muslim ones. Anyway, will process all that data properly later and get it up here... For the moment, I think it is safe to argue that historically venereal diseases have been a very effective way of removing large numbers of people from the gene pool, and that religion is one effective way of combatting this problem.


Marco said...

Your asserted link between religion and low death rates due to venereal diseases appears self-evident to me. I don't quite know what various group selection theories are dismissed by evolutionary biologists, but I will research your interesting point!

Dr. Clam said...

Here's a link to an atheist evolutionary biologist taking Dawkins apart on this point.