I’m not sure why Neil deGrasse Tyson is suddenly tw**ting pronouncements about evolution, but he is. Sadly, they’re wrong.

If there were ever a species for whom sex hurt, it surely went extinct long ago. — Neil deGrasse Tyson (@neiltyson) March 11, 2016

Well, that’s wrong on several levels. First of all, sex is painful (if animals do feel pain) in many species. The one that first comes to mind, of course, is the domestic cat, in which males have barbed penises that apparently don’t feel so terrific to the female during copulation. We’ve all heard the howling of cats in flagrante delicto! And is sex pleasant for male mantids or spiders who get eaten, post copulo, by their mates?

Some arthropods, like bedbugs, have hypodermic insemination, in which males bypass the female’s genitals and inject sperm right through the body wall, with the sperm finding their way to the eggs. It’s not clear why this is done, but it’s likely that it evolved to obviate the “sperm plugs” that some males put in females after copulation to block access by subsequent males. You can get around them by injecting sperm into the hemolymph. As Wikipedia notes, this can be injurious to females—even if the females don’t feel pain:

Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female’s abdomen with his penis and injects his sperm through the wound into her abdominal cavity (hemocoel). The sperm diffuse through the female’s hemolymph, reaching the ovaries and resulting in fertilization. The process is detrimental to the female’s health. It creates an open wound which impairs the female until it heals, and is susceptible to infection. The injection of sperm and ejaculatory fluids into the hemocoel can also trigger an immune reaction in the female.

Other species, including worms, rotifers, and snails, do the same thing. Why do the females put up with it? Well, maybe they can’t evolve a defense—remember that evolution isn’t perfect. And what matters is the net reproductive advantage of the genes for traumatic insemination, regardless of whether they occasionally cause injury, pain or even death. A female spider who kills and eats her mate has more eggs than one who doesn’t, for she gets that extra nutrition from the noms. If her benefit to egg number outweighs the reproductive cost to the male of giving his life—remember, genes for killing males after mating reside in both sexes, though they’re expressed only in females—then those genes will increase in frequency. The same goes for genes for traumatic insemination, whose benefit when they’re in males can outweigh the detriment of the process to females.

In fact, sex can be unpleasant or injurious to both males and females, so long as the reproductive advantage of unpleasant sex is better than not having sex at all, which it will be. Of course, natural selection will act to make sex less “unpleasant” for animals if it can—so long as there is genetic variation to improve matters. But that variation doesn’t always exist. Female cats must suffer because the male’s barbed penis, which appears to hurt her, also stimulates her ovulation.

Finally, you can fix a gene that is deleterious in both sexes without driving a species extinct. Imagine, for example, a gene that reduced the number of acorns in an oak tree by 1%. That would be deleterious, but such a maladaptive gene can rise in frequency by genetic drift alone, or if it’s tightly linked to another gene that is sufficiently beneficial to outweigh the reproductive cost of the linked acorn-reducing gene. If the population size of oaks isn’t limited by the number of acorns produced (say, if it’s limited by the amount of habitat), the species won’t go extinct. After all, each time a species improves its gene pool when an “adaptive” gene is fixed, the species was perfectly viable before that happened. It wasn’t necessarily going extinct before its gene pool was improved.

Well, so much for that. Apparently a lot of biologists called out Tyson on Twi**er for his error, but I haven’t looked (I rarely read other people’s tw**ts.) But yesterday Tyson made yet another evolutionary gaffe, and I’m sure he’ll get grief for this one:

If you have a gene for celibacy, you didn’t inherit it. — Neil deGrasse Tyson (@neiltyson) March 12, 2016

Umm. . . what about genes for sterility of workers in termites, bees, wasps, and naked mole rats? It is indeed possible that genes impeding reproduction can be fixed if they’re adaptive in relatives, as they presumably are in these species. And there is no doubt that there are indeed genes that cause “workers” to become sterile under natural conditions.

I’m not sure why Tyson is making these pronouncements. Maybe he knows they’re wrong and is trying to taunt biologists, but I doubt it—that’s not like him. Readers are welcome to speculate.