Saturday, October 12, 2013

Science is not a just-so tale

In the New York Times, Piet van den Berg and Tim W. Fawcett tell us that it is a near universal phenomenon in human cultures that human parents try to influence their children's choice of mates, and since it is universal there might be an explanation from evolution for this behavior.  So they computer-modeled this.  Simplified, evolutionary success - having more successful offspring -  means parents invest in their daughters' children, and this leads daughters to be less picky about choosing men who will help them raise children and further this results in parents' trying to pick more responsible son-in-laws.

The first problem with this is that cultural evolution would produce exactly the same results - that is, this behavior need not be encoded in our genes, but in our cultures.

But there is a bigger problem.  The authors tell us:

When thinking about mate choice, the natural starting point is the theory of sexual selection. This theory, which focuses not on the struggle for existence but on the competition to attract sexual partners, has been hugely successful in explaining the diverse courtship behaviors and mating patterns in the animal kingdom, from the peacock’s flamboyant tail to the chirping calls of male crickets.
We are told that the evolution of the peacock's tail can be explained by the peahen preferentially choosing to mate with peacocks with more flamboyant tails.   This is a nice, intuitively plausible theory, and it leads to a definite prediction about the  observable behavior of peahens.  So surely there is an extensive literature of peafowl observations confirming this nice theory.

To my dismay, what Google gives first is this:
Peahens do not prefer peacocks with more elaborate trains
Animal Behaviour, Volume 75, Issue 4, April 2008, Pages 1209–1219
Further search reveals that what peahens do is still a matter of some controversy.  Also, putting aside whether peahens prefer peacocks with more elaborate trains or not, in an experiment with peahens randomly mated with peacocks, those matings with peacocks with more elaborate trains produced more eggs (so maybe something else is at play, not sexual selection).

Now, Google is perhaps a bad way to approach this, but for something so central to this evolutionary theory of sexual selection, I would have thought that the research was all done and settled and much before 2008.   It seems to me that these just-so stories from evolution have made a huge number of people forget what science really is - it is not a set of plausible stories that work in computer simulations (or in mathematical computations); it is the confrontation of theory/model with the real world.  Figuring out how evolution works is not a matter of coming up with plausible scenarios.  This same rot we see in particle physics.  Given that the theory of sexual selection "has been hugely successful", I'm hoping there is a whole literature out there that sews up the case of the peacock's tail.