|Sunday, September 17, 2006|
David Brooks, Neuroendocrinologist: Having digested Leonard Sax on 'the emerging science of sex differences', David Brooks has been continuing his education in neuroscience by reading Louann Brizendine ('Is Chemistry Destiny?' 9/17/2006) (Via Language Log.)
Reading these efforts to exploit a murky scientific picture to support prejudice, I keep coming back to what seems to me a prevalent misconception about the implications of process conservation in evolution. The fact that some sex-associated process may be conserved in evolution does not mean that the process is used always in the same way, or that other processes may not be able to achieve similar outcomes. A critical insight of evo-devo is that conserved processes are loosely coupled, and have a wide operating range and outputs depending on inputs from other processes and the environment. Think of a conserved process as a subroutine. The fact that a particular subroutine is conserved between successive versions of a program does not mean that it is called by other subroutines in the same way in the different versions. Highly-conserved subroutines are those that are broadly useful, meaning that they can be used to achieve a wide range of results depending on context. Sex hormones may bias the operating points of various conserved processes, but that does not mean that the processes cannot compensate through other feedback loops to achieve effectiveness in various cognitive processes. Indeed, it would be surprising if those processes would have survived natural selection if they were so sensitive to highly variable hormonal environments. Subroutines that do not carry their weight in a wide variety of conditions stop being used and die out.