I detect some familiar ambiguities in this thread.
Those who prefer a 'nuture-driven' view of behavior often seem unwilling to accept that behavior can have a heritable component WITHOUT any loss of 'free will' on the part of an organism to express the behavior or not. What they really object to is 'behavioral determinism', not its heritability. And behavioral determinism is just plain wrong.
Nor is it essential to identify a particular gene for a particular behavior in order to demonstrate some level of heritability for the behavior. The underlying genetics is really of little consequence unless you happen to be interested in it. It is enough to demonstrate that one can select for an increased frequency of expression of a behavior in a population to show that it has heritability.
For example.
Say I want to breed houseflies that will be more attracted to vinegar than to sugar water. As flies emerge from pupae I put them in a cage as naive individuals with two bowls, one with each solution. Every time I get a fly that orients first to the vinegar, ignoring the water, I put it aside and breed it with another that responded the same way.
Maybe this will be < 5% of flies in the initial population, but
I can almost guarantee that, given enough generations, I can breed a population in which a significantly higher proportion of flies respond to the vinegar than did in the initial population. This would demonstrate some degree of heritability for the behavior - how much heritability there really is will determine how many generations are required to get a significantly different proportion responding.
The point is, some genetic configurations will make some individuals more likely to behave in one way than another, but there is no determinism of behavior at the level of the individual. You will always have lots of variation in behavior even among cloned or otherwise genetically identical individuals.
Genetics can only influence the *potential* for expression of a behavior in an individual - not its *actual* expression.
Individual behavior patterns are properties of a particular phenotype, and are not strictly dictated by the underlying genotype.
So yes, behaviors are subject to natural selection and they do evolve.
This message has been edited by EZscience, 05-05-2005 03:30 PM
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