BoundedRationality_TheAdaptiveToolbox.pdf

Evolutionary Adaptation and Economic Concept of Bounded Rationality 79
Economist: Am I right in interpreting the look on your face that the list of assumptions
under which optimality fails must be quite long, and that you are
unwilling to go through all of this with me?
Biologist: Not exactly. I am not unwillingto do this, but it would be a rather comprehensive
course in evolutionary theory, and I'm not sure that the bar stays
open that long. Theoreticians have tortured their minds throughout this century
trying to capture the spirit of Darwinian adaptation in the light of what
we now know about the mechanics of reproduction. Repeatedly, it looked
as if facts in genetics were blurring the Darwinian picture to such an extent
that Darwin was said to be dead. And then we saw his resurrection.
Economist: Not bad for the founder of a religion!
Biologist: Stop teasing! Let me talk seriously about three major criticisms. The
first stems from the idea that most replacements of genes in the genome are
the result of selectively neutral chance events rather than Darwinian select
tion. This idea has created the controversy about neutral evolution. Let us
play the devil's advocate and assume that indeed the majority of changes in
the genome are due to random drift. Even then we would still have to explain
why the male stickleback has a red spot on his belly. Believe me, any
male stickleback without a red spot will have a hard time attracting females
and will most certainly fail to reproduce. To mate or not to mate: this is what
the spot is about!
We would contradict ourselves if we were to assume that the genes responsible
for the spot undergo neutral evolution. Whenever we talk about
fitness maximization, we are addressing a problem where nonneutral selective
forces can be identified. These are the problems Darwin addressed in
his work, just as these are the problems that have been overlooked by some
advocates of the neutrality hypothesis.
Economist: And the other two criticisms?
Biologist: Well, the second one is that Mendelian genetics and recombination
can impose constraints on phenotypic evolution, so that phenotypic optima
and Nash equilibria may not be permitted by these constraints. One can argue,
however, that evolution will successively remove these constraints and
finally arrive at the phenotypic optimum if there is enough time before the
environment changes. I like to compare this course of a population with a
streetcar 3 that comes to a halt at various stops along its route before it
reaches its final destination. Only the final stop has the optimality and Nash
equilibria properties that we have discussed so far. The population will not
stay forever at such a final stop: one reason being the changing environment;
another being the possible occurrence of selfish genetic elements.