Since all of the physical world is subject to cause and effect natural science,
where everything occurs as a result of what preceded it,
free will would be IMPOSSIBLE to confirm scientifically.
It would absolutely require a belief in the supernatural.
I admittedly cannot prove that the supernatural doesn't exist,
but in as much as I've never had a supernatural experience of any kind to my knowledge,
I certainly can't be inclined to believe that it does.
Consequently, free will is a matter of belief, not science,
and even if we all proceed in our lives as if free will does indeed exist,
there's no proof that we're even doing that of our own free will.
You allude to humanity's separation from the remainder of the animal kingdom.
I don't see any evidence of that, either.
We're a dominant species because of our intelligence,
but in terms of our physical prowess,
we can't even count the species that would kick our asses in unarmed conflict.
I was a professional boxer and an adolescent tiger would show me how much that proves
if it were inclined to do so.
Again, I'm not claiming that you're wrong, Oom.
Understand that.
You should, however, be less dismissive of alternate beliefs on these matters,
and also less inclined to stipulate your own as if they were fact.
Free will is a belief and very far from a proven fact.