Is the yeti actually some hybrid of ancient polar bear and brown bear? University of Oxford geneticist Bryan Sykes has analyzed DNA from what's purported to be yeti hair samples.
From The Guardian:
Sykes's team looked at the 12S RNA gene, something that has already been analysed in all known mammalian species. By comparing his samples with those in GenBank, the international repository of gene sequences, Sykes was able to identify the animals that the hair might have from. "In the case of these two yeti samples that we're talking about, they matched a sequence in the GenBank from a polar bear jaw found in Svalbard, which is at least 40,000 years old." This was around the time that the polar bear and the related brown bear were separating into different species….
Sykes said the results had been submitted to a journal for peer review, so other scientists will be able to examine the results more closely as soon as they are published. He is aware of the limitations of his analysis, saying that there was only a limited amount that could be learned with the hair. "It's 40 years old and not much DNA there really. The next best thing to do is to get an expedition together to find one and see what one is like in the wild and to see if any aspects of its behaviour are more likely to be identified as a yeti. And genetically to find out how much polar bear is in this animal. It might be a hybrid or a new species of bear. But we can't tell all this from one hair sample."