To be clear on this, since I haven't seen it in the rest of this... discussion...
evolution does not occur because of use or practice alone, as another post implied. Evolution begins with random mutation. That mutation, if not corrected by the enzymes constantly fixing errors in our DNA caused by one of many environmental factors, will remain and proliferate within the organism it originally occurs in. This mutation must occur in the gametes, the things that eventually become fertilized offspring. If it doesn't, then nothing will happen to the species as a whole. The mutation itself doesn't actually have to do anything, it could be as small as altering a sequence of genes that doesn't even produce proteins, which build everything in your body that actually possesses your own DNA, or the mutation could alter how your cells interact with their environment. The mutation could even be so large that it causes a visible difference in between the organism and its parent.
The random mutation then persists as the organism grows, and might potentially be transferred to that organism's offspring when said organism reproduces. If this is so, then the mutation gets to interact with a new environment. Other mutations might stack with this one, and as they do, new traits might develop. The general theory is that the organism with the best tools to survive will survive and produce more offspring, but there's always the hardship of being young, and ecological factors as well as energy gathering related factors to be considered. But the most important factor in determining evolution is gene flow. One must survive long enough to, and be successful in, copulating with another organism within the same species, and this must continue for several generations, preferably with more and more offspring each time, for a trait to really be established within a species.
This turned into a rant, for which a apologize, basically my point is that evolution does not occur because you try to do something, or because something would be useful to you. Your gametes are altered in some way, and then when that gamete is fertilized, it grows into an organism with that random mutation present, and if it is useful, then it might become a tool for that organism to employ in their own survival. The trait exists before it is ever used, and once it exists, it is generally refined through breeding based on gene flow. And this gene flow generally results in the organisms with the best versions of the traits who survive to a reproductive age, can find a mate, and successfully copulate with them producing offspring that survive better in their environments.
My source: Campbell Biology, 9th Edition