In today's WTF science news, two separate studies suggest that modern allergies may stem from long ago human-Neanderthal sex. Thanks, Obama.
As absurd as it sounds, the studies make sense. Long ago humans were well-adapted to pollens and other environmental stimuli, but Neanderthals and other now-extinct hominids weren't. When the two got hot and heavy, their children came away with the Neaderthal's genes regulating some immune responses. These three Neanderthal genes have remained pretty much the same through time, leaving you popping Zyrtec this morning to avoid looking like you went on a bender last night.
It isn't all bad, though. These genes provide the body's first line defenses against foreign invaders like bacteria and fungi, and actually keep you pretty healthy. Unfortunately, they also overreact to things like pollen, triggering allergic reactions to otherwise harmless substances. Still, if I have to choose between influenza or hay fever, pass me the Zyrtec.