On this small, dirt ball called Earth, there are hundreds of sexual reproduction strategies. Praying mantises bite the heads off their lovers, while birds put on elaborate courting displays to attract a mate. This raises a question, one that has haunted scientists for decades: do aliens have sex? Seriously, what are the reproductive strategies of extraterrestrials? How do aliens procreate?
When you get right down to it, extra-terrestrial life is one big question mark. The biology of these organisms is extremely hard to predict. They have evolved in completely novel environments, from the human point of view. Think about how weird the platypus is, and that is only Australia-level weird. Other-planet-weird is a whole different ball game.
Like all pressing questions of science, this one has generated many theories. Here are some of those theories, ranging from the logical to the out-of-this-world.
Aliens Might Reproduce Through Cloning, But Not All the Time
It's possible that aliens reproduce by cloning, explains evolutionary biologist Dr. Sarah Otto. Purely asexual reproduction, however, is not in and of itself a viable long-term reproductive strategy. Without any ability to produce genetic variation, the slightest change in environment would have devastating consequences.
On earth, some species such as aphids clone themselves in times of plenty. This makes it easier to reproduce quickly. In times of scarcity, however, they resort to sexual reproduction. This allows for genetic variations, which translate to different survival strategies.
Aliens Might Use Hermaphroditic Reproduction, Especially If They Stay Still
According to evolutionary biologist Dr. Sarah Otto, it is quite possible that extraterrestrials would be hermaphroditic: that is, they would have both male and female sex organs on the same organism. This gives the organism the ability to reproduce quickly, since it doesn't have to find a mate.
Hermaphroditic reproduction would be most beneficial to a stationary species, more akin to a plant than an animal. Slugs are an example of a hermaphroditic animal on earth.
Aliens Might Have More Than Two Sexes to Choose From
Sexual reproduction isn't limited to the male-female dichotomy, evolutionary biologist Dr. Sarah Otto says. Sometimes there are A, B, C, and D choices on the menu. While some species on earth follow this pattern (like the Norway lobster), usually only two partners engage in any given reproductive act. So as far as we can tell, an alien orgy would be more for fun than strictly procreation.
Aliens Might Practice Gene Swapping, Either by Mating with a Partner or by Eating Them
Gene swapping is the norm for life on earth, so it follows that the model could extend to the stars. Not all forms of gene swapping involve sex, however. Bacteria, for example, swap genes when they eat other bacteria. This is because they are prokaryotes, meaning they don't have membrane-enclosed nuclei.
This leads scientist to conclude that the evolution of reproduction in an alien species would have a lot to do with whether or not their cells have enclosed nuclei.