Self-Love Is Important, but We Mammals Are Stuck With Sex

If Galentine’s Day had an animal mascot, it would have to be one of the species whose females can reproduce without a mate. Nearly all animals make more of themselves the traditional way, by combining eggs and sperm. But some have an alternative called parthenogenesis: no males needed.

No matter how many romantically frustrated mammals have wished they could truly go it alone, though, a genetic quirk means we still need sexual reproduction. For now, parthenogenesis is for the birds (and the bees), the fishes and the reptiles.

One of the most famous recent cases of parthenogenesis involved California condors, an endangered species. In 2013, Leona Chemnick, then a researcher at the San Diego Zoo Wildlife Alliance, discovered that two male chicks in the condor breeding program had DNA that didn’t match that of the fathers in their cages — or of any other male. The chicks’ DNA only matched their moms’.

Ms. Chemnick caught Oliver Ryder, the zoo’s director of conservation genetics, on the way to his car and asked him about the odd data she was seeing. He explained to Ms. Chemnick that any such condor chicks must have come from eggs that were not fertilized by sperm.

“We were literally walking out to the parking lot and had this eureka moment,” Dr. Ryder said. “We didn’t have time to dance or anything.”

By the time the two scientists and other colleagues published their parthenogenesis finding in 2021, the two unusual chicks, or parthenotes, were long gone. They’d both died young, at almost 2 years and almost 8. Their mothers both had many other offspring, though, conceived with their mates in the usual way (despite headlines declaring virgin births).