well no, actually. different species of bears live in different climates. adaption to ecological changes or variations, new species or a change of species happens.
man adapts himself to different climate by using clothing or other devices ( part of what makes us human , so does not apply to this scenario ) but actually humans have done this too, witness the different "races" of people.
you and a few others try to uses other dimensional beings as an excuse all the time, do i need to go back and makes quotes ?
many scientists believe nothing. science is about testable facts. other dimensions cannot be tested. show me any scientific data that proves for other dimension , other then speculation.. there is none. there is not many scientists , non a one who have testable scientific data on the subject.
bigfoot, if real would have to be of this dimension. bound by reality , biology and rules of time and space of this known universe.
it is not , in an way, commonly observed a extra dimensional being . there is nothing that would suggest that, scientifically or otherwise. statements like that are laughable at best.