If we assume being reactionary to one's environment is purely advantageous (with no negative effects when taken to the extreme), then yes it would have died out (theoretically). However, freedom to deviate creates diversity (among possibly other advantageous traits) and over-adaptation to one's environment can cause a species to "put all its eggs in one basket" and eventually become extinct.
However, freedom to deviate creates diversity (among possibly other advantageous traits) and over-adaptation to one's environment can cause a species to "put all its eggs in one basket" and eventually become extinct.
You seem to be ascribing magical properties to one source of randomness. What special 'diversity' is being caused by 'free will' that one couldn't get by, say, cutting back a little bit on DNA repair and error-checking mechanisms? Or by amplifying thermal noise? Or by epileptic fits?
(Bonus points: energy and resource savings. Free will and no DNA error checking, two great flavors that go great together!)
Given the spike in free-will debates on LW recently (blame Scott Aaronson), and the usual potentially answerable meta-question "Why do we think we have free will?", I am intrigued by a sub-question, "what would it feel like to have/not have free will?". The positive version of this question is not very interesting, almost everyone feels they have free will most all the time. The negative version is more interesting and I expect the answers to be more diverse. Here are a few off the top of my head, not necessarily mutually exclusive:
Epistemic:
Psychological:
Physical:
For me personally some of these are close to the feeling of "no free will" than others, but I am not sure if any single one crosses the boundary.
I am sure that there are different takes on the answers and on how to categorize them. I think it would be useful to collect some perspectives and maybe have a poll or several after.