[Son of Sephiroth]

Yes. Subtle things will happen whic will effect your mental chemistry which in turn will make you do something

eg. There is a subtle change in pressure over france. This Lower pressure draws all the clouds in england towards it. Thus, it is sunny in england today. Because it is sunny, it reminds you of happy times you have had in the sun, so you feel good. this good feeling makes you crave more of it, so you go outside. You meet fellow "I like ths sun" people and what's this? their Immune system is subtly different from each other and their faces HAPPEn to be more symetrical? Attraction occurs and thus, the genes inside you manage to continue to the next generation (don't ask me to explain how) :P.

And all this happened because of a pressure difference.