Evolution isn't a steady process. When the environment changes, the organisms have to adapt quickly or perish. A theory known as punctuated equilibrium accounts for this. Any changes in then environment brought on by natural or artificial changes will cause animals to evolve to those changes. It may be that they just have to migrate where the climate is more suitable. When you look at geologic sequences, you can often see the different environments as the climate changed and a new suite of animals and plants took over.
<span>It is fantasy to claim that the "old" environment was stable before humans came along unless you live in the tropics. There was a mile of ice over NYC and Chicago 15 thousand years ago. </span>
<span>Geologic changes can affect evolution by creating population splits which allows for speciation. For example, the thrusting up of a mountain range may cause one population to split into two. The separate populations may then evolve on their own sometimes into new niches. One population may stay relatively similar and the other may change dramatically.</span>
