Aside from everything else about this story about why we yawn, which is apparently to cool our brains down...
Is anybody else really reminded of Terry Pratchett now?
In the Discworld series, Troll brains became less and less effective in heat, because they were silicon-based. This actually forced one character to wear an artificial brain-cooler in one of the books.
I never would have thought the same thing would apply to human beings too.