I will offer a common sense approach to explain why Bigfoot does not exist. The first assumption I am forced to make when weighing the existence of Bigfoot (or Yeti), is that he must be really stupid. Even the cavemen had fire, so if bigfoot was as smart as a Neanderthal, he would have fire too. And since he is living in the Pacific Northwest, it gets really REALLY cold, so not having fire would prove him completely stupid. And if he did have fire, Bigfoot would be spotted from the air as every Bigfoot family would have a campfire every night. Stupidity argument #2 would be that even the lowest of intelligent humanoids enjoy the value of clothing. It doesn't take a brain surgeon to figure out that if you are freezing, to cover up - especially your feet. Yet all supposed sightings of Bigfoot are of naked Bigfeet.Ok, so we have established that Bigfoot is stupid. That being said, we can assume that he would make mistakes, and stumble into campsites by accident. He would also probably hang out on the side of the highway inspecting roadkill and occasionally become roadkill himself. With no intelligence, there is no way that Bigfoot could be so remote to retain a clandestine existence.
Also a low intelligent being would not bury (or burn) dead bodies. So therefore, if there was a viable breeding population, a dead Bigfoot body would eventually be found. You cannot use the excuse that animals would scatter the remains, because I assume the leading cause of death would be freezing to death (see paragraph 1). So a frozen body would be covered with snow and at some point would be discovered. I mean, we found that little missing link guy and he had been around intact for thousands of years.
The only concession I will make is that he could be an alien and not spend much time on the surface at all. After all, the theory is that aliens manipulated our DNA to create Homo-Sapiens, well Bigfeet could be the rebellious hippie alien proto-types that just come the surface to land in the middle of nowhere to grunt.
