I think “free will” might just not be a useful concept. If free will means “the choices people make are not determined by causes” then free will would just look like people acting entirely at random.
ETA: The more interesting question (to me) is how this changes how we judge people, if at all. If a person is an asshole, obviously that’s because of genetic and environmental influences. Do we excuse it either way? (In which case you literally can’t ever hold anyone morally accountable for anything). Do you excuse people only when the causes are environmental? Only when the environment is extreme or the genetic difference is considered a “disease”? But what justifies the difference?
ETA: The more interesting question (to me) is how this changes how we judge people, if at all. If a person is an asshole, obviously that’s because of genetic and environmental influences. Do we excuse it either way? (In which case you literally can’t ever hold anyone morally accountable for anything). Do you excuse people only when the causes are environmental? Only when the environment is extreme or the genetic difference is considered a “disease”? But what justifies the difference?