We humans (or at least, the geekier specimens among us) seem obsessed with human-on-alien action. From the countless conquests of Captain Kirk to the untamed Na’vi beauty Neytiri, science fiction is replete with tales of uninhibited extraterrestrials that know just how to get our motors running.
But is it really likely that even if we’re not alone in the universe, our galactic neighbors will want to pay conjugal visits? Probably not.
The first, and perhaps most obvious obstacle, is that there’s no reason to assume aliens will be humanoid. Blue-skinned babes with scantily covered goodies may sell movie tickets, but for better or worse, James Cameron did not design the universe.
If there is a chance of humanoid aliens existing, it may lie in convergent evolution. Convergent evolution is the evolution of similar characteristics in species that are not closely related, in response to dealing with similar environments.
An example of convergent evolution is the similarity between the wings of bats, birds and pterodactyls. Each of these critters evolved wings independently, as a result of facing similar challenges in nature.
Even if aliens could resemble humans, it’s unlikely they’d share the same internal makeup. Life on Earth is carbon-based, but carbon might not even exist on alien worlds.
Last, but certainly not least, alien life probably wouldn’t be based on DNA as we know it. All life on Earth shares that basic blueprint, and we’re still unable (and generally, unwilling) to mate with our cousins in the animal kingdom. It has been theorized that humans once interbred with Neanderthals, but even that is uncertain.
Seth Shostak, senior astronomer at the SETI Institute in Mountainview, Calif., put the problem this way:
“It would be like trying to breed with an oak tree,” he said.
Of course, all of this just means that humans are unlikely to want to have sex with aliens, and very unlikely to be able to successfully reproduce with them. It doesn’t technically preclude sexual activity for the very intrepid among us.
In a piece for Wired, Chris Hardwick theorized that humans might be objects of sexual desire for very kinky aliens. As he says (somewhat more graphically than I’ll put it here), alien-on-human action could be a very lucrative part of the alien adult entertainment industry.