it looks to me that you`re saying that humans disrupt the natural order, and animals follow it - therefore this deviation from nature in humans must be indicative of free will. I don`t see how we humans are beyond the natural order... and if we seemingly disrupt it - it will only be temporary. Either we`ll be forced to change to avoid immenant destruction, or we will be destroyed. Either choice that follows will be the result of external causes. I believe that even internal states are caused by the external - nature vs. nurture, so nothing goes uncaused.
In nature, cannibalism (which seems to be in direct violation to evolution seeing as members of the same species would not kill their own because that would be detrimental to the species as a whole) actually does occur when competition within a species becomes unacceptably high. As it turns out, certain organisms will resort to cannibalism when individual organism`s chance for survival depreciates to an intolerable level due to high competition. The solution therefore, is to eat the competition to restore a population balance.
Therefore, the destructive behaviors you mentioned, do occur naturally when levels of competition are too high. I contend that Self serving behavior IS natural, and is necessary in nature`s balance - it helps to control unsustainable population growth.
We can see this at work in humans as well. Humans are growing at an exponential rate. Exponential growth can only be maintained in an environment with unlimited resources - since earth`s resources are limited, this will create competition. I`m not saying we will revert to cannibalism, but there are various mechanisms that nature implements to control populations.
Ecologists have suggested that overcrowding in cities result in increasingly poor sanitary conditions, coupled with very close proximity of individuals to each other. This makes cities prime for outbreaks of pandemics. Many ecologists have predicted this to be the case, and the chicken virus in China a couple years ago was predicted to be that pandemic. Fortunately it wasn`t so, but with our present levels of growth, we can expect a collapse to happen in time - so this `unnatural behavior` you refer will not continue indefinitely.
All things are subject to natural laws. I see no exception to this, even in humans. The mere fact that we can conceive of possible futures, does not mean we have free will. At what point in evolution does a species attain free will? are there differing degrees of free will between species?
A computer that provides a user with various options, cannot itself freely choose which course of action to take without someone external to program it, and tell tell it what to do. Thus, even if one day we could create a computer that seems to make decisions without the input of a user, i don`t think it would have free will because it`s internal mechanism isn`t freely chosen. The fact that our internal states are caused by outside factors (nature vs. nurture), to me points to the idea that we don`t have free will. The computer afterall is just a mass of physical things - all of which are subject to deterministic laws. If humans are simply a more evolved animal, should we not also be subject to determinism?