I see the words "nature" and "essence" as both carrying with them the same fundamental meaning. When people talk of nature in general, usually they are referring to the essential aspects of life. This is why I would't say that the evolution of nature, or this essence we speak of, is necessarily blind, especially to the species which nature consists of. To say that nature makes the choice for the species, to me at least, suggests that nature and the species are two separate existences. I would say it is more logical to say that they necessarily choose together, and if there are choices made that usually entails some sort of purpose, or else a theory of evolution which involves some sort of "natural selection" could not be possible.

De-evolution is a tricky concept for the very reason that evolution occurs purposefully. I don't really see a difference between de-evolution and evolution because all change that occurs is governed by the reasons for it. Even if a species may seem less advanced from what it evolved from, which I'm not sure is ever the case, it only seems that way from our perspective. Nature evolves how it evolves, and its purpose for evolution is to maximize survival within a given set of circumstances.

If we hold that genes and/or unconscious impulses do/can influence individual personality or "human nature," and thereby personal choice, then no. It follows then that so-called "freedom of choice," "unlimited freedom" and the much vaunted "free will," are myths. Even if we simply posit the mere possibility (say, a one in a trillion chance) of said influences existing, the answer is still no. Thus, existence cannot precede essence. While I certainly believe that Sartre does in fact have much to recommend his thought, for me this conclusion must necessarily undermine the entire Sartrean edifice. Unlike Sartre (a "hard determinist," to be sure) I am, generally speaking, a "soft determinist." One can, of course, easily argue that "determinism" either is or is not. I strongly recommend Nietzsche on the question of "free will" and its religious and legal implications.

Correction: "hard determinist" should read "non-determinist." Sorry.