Does Behavioral Genetics Indicate Room for Free Will?

Economist Bryan Caplan thinks that he thinks the answer might be yes:

Virtually every BG [behavioral genetics] study partitions variance into three sources: genes, shared family environment, and non-shared environment.  Typical estimates are something like 40-50% for genes, 0-10% for shared family environment, and 50% for non-shared environment.

And what exactly is non-shared environment?  Everything other than genes and family environment!

….suppose human beings had real, honest-to-goodness free will.  If it made a difference for behavior, where would it show itself?  In the BG framework, it would be filed under "non-shared environment."

….If you could fully account for a person's choices using genetics and measurable environmental variables, you'd count it as a confirmation of determinism, right?  Well, if you buy this argument, you also have to buy its mirror image: The harder it is to account for a person's choices using genetics and measurable environmental variables, the stronger the case for free will.

…..Identical twins raised together are still, in many ways, very different.  The believer in free will can simply say, "The good twin and the evil twin just made different choices."  The determinist, in contrast, can only ask for a blank check: "One day, we're figure out the hidden forces that caused them to be so different.  Until then, bear with us."

…..I strongly suspect that if non-shared environment's contribution to behavioral variance were a lot smaller, determinists would be heralding the result as "proof" of their position. 

In May 2003, Ron Bailey interviewed philosopher Daniel Dennett about determinism for Reason magazine. Whether you click on this link to read it may or may not be up to you.