The Evolutionary Psychology FAQ

Edward H. Hagen, Institute for Theoretical Biology, Berlin

What about gene-environment interactions?

To say that the phenotype is mutually determined by genes and environment is simply to make the trivial observation that the phenotype is a physical system; thus its dynamics, like the dynamics of all physical systems, is subject to the influence of other, coupled physical systems.

Chemistry happens.

It is false, however, to infer that this process is, IN GENERAL, adaptive. If Murphy's law has any force, most environmental perturbations on developmental processes will disrupt the normal development of the target adaptation. I would therefore expect that many developmental mechanisms exist specifically to buffer environmental variation, thus ensuring proper development of complex adaptations. Stated another way, I suspect that the body is designed to ensure that developing systems only 'see' the environmental variation they are supposed to see; much, if not most, of the time, this will involve shielding developing systems from variation, not exposing them to it.

The exception to the latter, of course, is environmental variation that is critical for the development and performance of the adaptation. In these cases, specific development mechanisms have almost certainly evolved to sample the variation, and to then 'tweak' the target adaptation to enhance its performance under these conditions. In some cases, the 'tweaking' will be quite dramatic, such as acquiring a native language or learning social norms.

Here's an analogy:

You've just won the lottery, and want to have a tricked out SUV custom built for you so you can cruise the world's deserts. Do you:

a) request that the manufacturer build the SUV in a sandstorm so that it will optimally perform in desert conditions,


b) request that the manufacturer add specially designed equipment, such as tires with the proper treads and a bigger radiator, so that it will optimally perform in desert conditions.

The first is analogous to what I fear many people are thinking when they invoke 'gene-environment' interactions; the latter is analogous to what I think is actually happening most of the time.

Copyright 1999-2002 Edward H. Hagen