Whether it is the fountain of youth or the elixir of life, men have travelled the world looking for the key to increasing their longevity. They should be looking a bit closer to home, according to one leading researcher – although after they do, they might end up taking the years God intended for them. When it comes to increasing the lifespan of any male mammal, “there is one way you can intervene”: castration. Cat Bohannon, the celebrated author of Eve: How the Female Body Drove 200 Million Years of Human Evolution, said men went through life “smuggling two little death nuggets”, with research suggesting an orchiectomy can lend a few more precious years. Speaking at the Hay festival on Friday, Bohannon said castration was a “way to make male mammals live longer”. This effect was observed in American men in the mid-20th century who were institutionalised, usually because of mental illness, and castrated, and in Korean eunuchs. The castrated men lived longer than their “regularly balled peers”. “You can castrate it. Cut off its balls. Don’t try this at home,” added Bohannon, a researcher with a PhD from Columbia University in the evolution of narrative and cognition. While it used to be thought that the average lifespan discrepancy was behavioural – “dumb boys doing dumb boy stuff” – it in fact “seems to have something deeply to do with the immune system and cellular repair”, she said. Males “get more infections” across their lifespan and “more cancer, and the prognoses in many cases tend to be a bit worse”. A 2012 study published in Current Biology found that the average lifespan of 81 eunuchs born between 1556 and 1861 was 70 years, which was 14.4–19.1 years longer than the lifespan of non-castrated men of similar socioeconomic status. Researchers concluded that the study “supports the idea that male sex hormones decrease the lifespan of men”. “So why is this? Why are so many men smuggling two little death nuggets?” Bohannon said. “I’m afraid we don’t really know. A lot of good science is being done in this space.” Bohannon said that after discussing “killer balls” on The Daily Show with Sarah Silverman, she got “very intimate” questions from men about their “testicular situation”. “I’m now ball chick, it seems,” she said. Bohannon also told a Hay audience that “someday we’re going to have an artificial womb”, though it may not be for hundreds of years, and that it would raise ethical questions. “Let’s be really utopian about this shit, OK. Let’s say it’s available to everyone, it’s not just a rich woman thing, it’s not just a white woman thing – whatever that means hundreds of years out – does it then become ever ethical to ask a person with a womb to become pregnant if it can be done outside of a body?” The technology would take a long time to develop, she said, because “it’s not simply a bag in which one has a baby, it’s an entire female body. Whenever a mammal is pregnant, that entire body is pregnant. “There are knock-on effects throughout the system, many of which have long-evolved to influence what’s going on in that womb – immunological agents crossing the placental barrier, et cetera. So that means we have to know a hell of a lot more about female bodies to try and build a fake one.”