As we all know, this will draw Skeptics and believers alike. I am not a biologist, nor am I a scientist. I have made my observation and I have been reading up, so bear with me.
Throughout time , man has grown accordingly to adapt his environment. Bigfoot, yes, it is a controversial topic. It displays characteristics that of both a bipedal humanoid and roughly, an ape. Scientists have currently suggested that Robust Australopithecines, a descendant of Gracile Australopithecine, a hominid that shared some characteristics that of ape and
Human, could possibly fit the criteria of Bigfoot.
First, to understand how Bigfeet were spotted around the world, we have to look into their possible origins. Ardipithecus, was a very early ancestor of present day man. It shared many traits with the African great ape, and was often debated to belong to the Chimpanzee branch. However, it was stated to be a proto-human due to the similarity of teeth with Australopithecus .Hominids expanded over the African continent over time. By roughly 3.7 million years ago , Ardipithecus had evolved to Gracile Australopithecine, and were heavily concentrated in Northern and Eastern Africa.
Eventually, Gracile Australopithecine became the Robust Australopithecines, and proceeded to grow outward, as shown in this picture.

Wolves and Dogs have successfully created a hybrid. I Hypothesize that an Early form of Homo Erectus and Robust Australopithecines successfully created a Hybrid of moderate height that had mostly ape like features. While its cousins evolved, the result of the breeding rendered it drastically less intelligent, and more or less, primarily instinctual.
There have been hypothesis’s that some of them killed off each other.
I believe, that as the hominids grew into Homo Neanderthalensis, they became more aware of their cousins. And with that, territorial battles ensued, and that they were killed mostly out of fear by crude weapons, like spears. As the last ice age came on, the Bigfeet had been victims of a pre-historical genocide and had grown thick fur coats thanks to their ape characteristics. Soon, they migrated to Asia. They found content within the Himalayan mountains were favored by natural selection, and adapted to the environment. Hence, the white fur and the Yeti.
As resources ran out at the end of the ice age, some of them instinctively searched for more food, and crossed over the land bridge, spreading through North America. As they adapted to their new home, their coats turned to a dark brown color, to blend with the trees in the forests they found safety in. Early Indian Tribes, I believe competed with them for land and food, which led to the slaughtering of the Bigfeet , and which pushed them back into the northern land, in the forests of Canada and North western America. As this would have been merely centuries ago, the populations are centered mainly in the deepest parts of large forests, and are low at that.
My sources are:
http://www.stanford.edu/~harryg/protected/chp18.htm
http://en.wikipedia.org/wiki/Homo_erectus
http://en.wikipedia.org/wiki/Neanderthal
http://en.wikipedia.org/wiki/Bigfoot
http://en.wikipedia.org/wiki/Paranthropus
http://en.wikipedia.org/wiki/Gracile_australopithecine
http://www.onelife.com/evolve/manev.html
