The answer is, your guess is as good as anyone's.
Evolution is a random process, driven by the environment in which an organism exists.
Change the environment sufficiently, and an organism will either have to adapt to it or perish. Thus it has always been. We 20th century humans have found a way to circumvent the process to a degree - by controlling our environment, we limit the degree of change our species is exposed to. However, we are still not immune. Even though we can moderate environmental forces to some extent, we still do not have the capacity to survive major geological or climatological upheavals.