From a way-cool NatGeo article:
Then one day more than 375 million years ago, it happened. One lineage of plants evolved pollen grains and seeds, and from then on nothing was the same. Let's not mince words. Pollen is plant sperm—two individuals per grain—surrounded by a single, often golden, wall that offers both protection and chariot. If the tension in the long story of plants was the distance between lovers, pollen was what would bring them together, over feet or even across continents. It was an evolutionary trick that transformed the world by letting strangers have sex.With pictures! Good ones, too. That said... I've always been in favor of sex with strangers to a certain extent... especially when you find yourself on a different continent (about which: a cheap-ass and blatant self-promotion ploy. And you know there may be more, for those of you who are new to EIP.). But back to stranger-sex: with suitable caution, of course. We must be politically correct.