Humans love to ponder whether alien life is out there, and what it might look like. So here’s a burning question: Would extraterrestrials have sex?
The question isn’t entirely prurient. The evolution of sex is a tricky subject. Sexual reproduction is costly. It requires finding a mate, convincing that mate to mingle DNA with you, and opening yourself up to the possibility of sexually transmitted disease or predation while you’re busy wooing.
All that considered, and it might not even result in viable offspring. After all, mixing and matching a genome is a crapshoot, said Sally Otto, director of the Biodiversity Research Centre at the University of British Columbia.
Potential parents “know their genome works in the current environment,” Otto told Live Science. “They know they survived to reproduce. And here they are, shuffling their genomes together with another individual. … You have no idea if that combination is going to survive and be fit.”
And yet, sexual reproduction is very common on Earth. And given the conditions in which sex evolved, it’s quite possible that aliens might get busy, too.
Not all life on Earth requires sex for reproduction. Amoebas, yeast and millimeter-long freshwater hydra all manage to create offspring solo, as do many invertebrates. So do some surprisingly complex animals: Virgin births have been reported in Komodo dragons, pit vipers and sharks.
There are species, like the tiny crustacean Daphnia middendorffiana, that can only reproduce asexually. But sex appears to go way back. There are few very old lineages that are entirely asexual, Otto said. [Photos: Bizarre Sex Lives of Hermaphrodite Sea Slugs]
Amoebas, for example, date back at least a billion years, long before multicellular life evolved. For a long time, scientists thought amoebas were purely asexual. In 2011, however, researchers from the University of Massachusetts announced that they had discovered amoeba sex.