I knew earlier in my life, either through someone telling me the fact of it or just passing along an old wives' tale, that we didn't know why we yawned. Well, we still don't know. It seems to serve a behavioral purpose more than physical one; the information on those with autism or schizophrenia was interesting. I also wasn't aware that you don't yawn while lying-- that in itself opens up a pandora's box of possibilities.
An interesting read.