i would say the purpose of life is only proliferation, it's the environment that provides the negative feed back for "self-sustaining". For example, deer with n

i would say the purpose of life is only proliferation, it's the environment that provides the negative feed back for "self-sustaining". For example, deer with no predators will proliferate until they starve to death and numbers go down to what can be sustained by their environment. If the environment can't sustain any then the population count goes to 0 to match.