One common activity on Star Trek was to boldly get busy

Star Trek Biology Explored in the New Book Live Long and Evolve  

If you’re like me, you’ve watched a lot of Star Trek. If you’re even more like me, you’ll read the new book Live Long and Evolve: What Star Trek Can Teach Us about Evolution, Genetics, and Life on Other Worlds, by Mohamed A. F. Noor, professor of biology at Duke University and editor in chief of the journal Evolution.

And being like me, you will turn immediately to Chapter 5: “Sex, Reproduction, and the Making of New Species.” Because ever since you first saw Captain Kirk canoodle with a series of apparently female, apparently humanoid organisms you’ve been like, “I gotta check the Statutes of Alpha III to see if that’s kosher.”

Closely related species do get it on and can even beget offspring. A horse and a donkey can produce a mule. A lion and a tiger can produce a liger. A polar bear and a grizzly can produce a pizzly. But a human being and anything not a human being can produce a court appearance.

Still, humans bonk nonhumans regularly (by which I mean often—though I don’t know about the actual ways and means) in Roddenberryland. “Given that interspecies mating is uncommon on Earth, it appears unusually common among the humanoid species depicted in the various Star Trek series,” Noor writes. “Indeed,” he continues, “attraction to members of other humanoid species does not seem noticeably weaker in any of the five series than attraction to members of one’s own species.”

So I called Noor and asked him what’s with all the outer-spacey interspecies mating? “It’s interesting the way the Star Trek series depicts it,” he responded. “They make it seem as though different species are no different from human ethnic groups or something like that, where, oh, this person is slightly exotic and therefore attractive. And that’s not what you expect if you’re looking at an actually different species. If we go to the zoo and we see a chimpanzee, we’re not attracted to it any more than it is attracted to us.”

In fact, depending on what fictional history of the Trek universe you subscribe to, a human being and a Vulcan or a Klingon never had a common ancestor and are the result of amazingly high-fidelity convergent evolution. Or an exceedingly ancient species (represented by the “Humanoid Progenitor” in The Next Generation episode “The Chase”) seeded the universe to force evolution to come up with all of us different types of bilaterally symmetrical, upright-walking intelligent space travelers. Which means Trek humans and the other species with which they’re bumping uglies (we don’t know how ugly) have no evolutionary relationship at all or that the relationship is far more distant than the one between us and chimps.

But we’ll grant the Trek writers a certain license so that they can include romance in their story lines—and because there’s only so much you can do to make human actors look like alien species you’d never meet for coffee.

(For some anatomically intriguing interspecies mating, see the best of all the Star Trek movies, namely Galaxy Quest, which is not really part of the franchise, in particular the scene in which Tony Shalhoub makes out with Missi Pyle, who starts caressing him with tentacles. To which Sam Rockwell echoes my earlier concerns when he says, “Oh, that’s not right.”)

If you assume a relatively close degree of genetic similarity among these humanoid species, “the interspecies mating is not so crazy,” Noor noted. “Rather than humans and chimps being the analogy, it’s more like humans and Neandertals.” And when Noor says “humans,” it’s shorthand for us modern humans, Homo sapiens sapiens. Plenty of other human species have existed, including the one categorized by some researchers as Homo neanderthalensis, a fully separate species, and by others as Homo sapiens neanderthalensis, just another subspecies. However you slice it, we know that saps and thals mixed it up—you’ve got Neandertal genes in your pool.

So here’s to the Trek universe’s interspecies residents, including B’Elanna Torres (Klingon-human), Deanna Troi (Betazoid-human) and, of course, Mr. Spock (Vulcan-human). As Kirk said at one of Spock’s funerals, “Of all the souls I have encountered in my travels, his was the most [Shatner pause] human.” Which Spock would have found deeply insulting.