After all, even if we put aside the direct ways in which our genes build our bodies (encoding how our tissues grow) and instead look at our abilities to “make the right choices” and exert “willpower”, we find that those are also greatly determined by genetic factors. Identical twins probably turn out very similar in good part because they have almost identical amounts of those qualities of mind.
Indeed. This is why I wrote:
I don’t think thin people are thin because of willpower.
Willpower was listed as just one factor. It wasn’t mean to be an exhaustive list of all factors.