In the B-movies of the 1950s, Earth found itself regularly invaded by all manner of aliens. But what trait did all these ETs share that made them want to invade our planet? Sexual frustration, apparently.
Top image: "Amor Alien" by Laura Molina.
As part of their "Science At The Movies" special issue, Scientific American has reprinted an 1995 article about the University of Illinois' May R. Berenbaum, who studied over 100 SF movies of the '50s to identify common traits amongst the invading organisms that plagued our planet. Her discovery? That, even if humanity had lost all the battles, we probably would've won the wars because of genetics:
In general, none of [the aliens] exhibit the opportunistic sorts of reproductive traits or characteristics of organisms that successfully colonize.
Well, that and the entirely fictional nature of said alien invaders. The problem isn't just that invading aliens didn't have the opportinity for, uh, "reproduction" - they also, apparently, weren't the greatest at planning:
Berenbaum and [co-researcher, Richard J] Leskosky found that 42 of the movies showcased either a lone invader or a pair. Only 21 films have the earth threatened by more than six intruders. The small initial invading force, combined with failure to go forth and multiply once they reach the planet, renders most movie aliens nothing more than short-term threats. The few invaders who do try to reproduce once they land make efforts that are biologically questionable. For example, the attempts of the title character in Devil Girl from Mars (1955) to mate with humans is "an undertaking fraught with hazards associated with postzygotic reproductive isolating mechanisms," Berenbaum and Leskosky point out.
If nothing else, this article can now forever be used as use in an elaborate chat-up scheme that will involve convincing the object of your affections that aliens have invaded, and the most patriotic thing you can do for your planet at that point is fuck.
Nothing Personal, You're Just Not My Type [Scientific American]