50 whys to look for genes: 4. Understand the basis of traits

Since the rediscovery of Mendel’s laws, it has been common to talk about genes for xx, where xx could be feeblemindedness, IQ, sports ability, procrastination, homosexuality, divorce, crime, fidelity, conservatism, liberalism, schizophrenia,…  (You choose xx; see what you get when you google “Is there a gene for xx.”)

There are many complications, including

1. is the trait a well-defined quality or condition? (see e.g., Poland 2004 on ‘schizophrenia”);

2. what is the evidence that the trait is determined by genes (e.g., if based on pedigrees, have they taken social/environmental conditions into account when these run in families too) and how general are these genes (e.g., extending Brunner syndrome beyond the Dutch family in which it was identified);

3. if a mutant gene is identified associated with an abnormal trait (e.g., for extra digits), it doesn’t then follow that the absence of the mutant explains the normal trait (i.e., 5 digits); and

4. using research that exposes mutant genes associated with abnormal traits leads one to think about complex characteristics developed through a lifetime of social interaction in binary terms, moreover, with one side of the binary being abnormal (e.g., think about genes for homosexuality, but not genes for heterosexuality, and think about sexuality as a binary not a diversity).

Reference: Poland, J. (2004). “Bias and schizophrenia.” Pp. 149-161 in P. J. Caplan and L. Cosgrove, eds. Bias in Psychiatric Diagnosis. Lanham, MD: Rowman & Littlefield.

(Introduction to this series of posts)