Public health advocates, when asked what single intervention would most dramatically prolong human life, tend to be unanimous:
A paper in this week's edition of Current Biology reminds us that there is another practice, long-established in some cultures, that more dramatically prolongs lifespan in people eligible to undergo it:
Unfortunately it isn't an especially practical intervention to prolong lifespan.
As long ago as 1969, a study of patients in U.S. mental hospitals showed that castrated patients lived an average of 13.6 years longer than intact patients. The mere fact that an appreciable number were castrated hints at the barbaric treatment of inmates in these institutions. Fair to say this was not a particularly representative population of castrated men, if such a population exists.
The new development involves the analysis of data from the Yang-Se-Gye-Bo -- an 1805 genealogy of Korean eunuchs. As Kyung-Jin Min, Cheoi-Koo Lee and Han-Nam Park explain in their paper:
The Imperial court of the Korean Chosun Dynasty (1392-1910)... had eunuchs ...[who]... lived with privileges: Korean eunuchs were conferred with official ranks and were legally allowed to marry, a practice that was officially banned in the Chinese Empire. In addition, married couples were also entitled to have children by adopting castrated boys or normal girls. The boys lost their reproductive organs in accidents, or they underwent deliberate castration to gain access to the palace before becoming a teenager.
The average lifespan of the 81 eunuchs for whom the authors could extract reliable data was 70 years. By comparison, contemporary non-eunuchs from families of similar social status lived an average of between 51 years (the shortest lived family) and 56 years (the longest-lived family).
Interestingly, out of the 81 eunuchs, three were centenarians. The current incidence of centenarians is one per 3,500 in modern Japan (the country with the highest survival to 100). Thus, the incidence of centenarians among Korean eunuchs was at least 130 times higher than in the most centenarian-rich modern society.
Eunuch longevity is also probably not due to cushy palace living. Kings and male royal family members only lived to averages of 47 and 45 years old, respectively.
This effect is never going to be subject to randomized controlled experiment on a representative population. A near-infinite number of aspects of the lives of eunuchs would have differed from the lives of other men.
But that is also the point. Extended longevity isn't simply due to the magical effects of lower testosterone on otherwise-identical bodies. Sex hormones change everything about our lives because they mediate the investments we make in reproduction. And for men that includes the jostling for status, the respect of other men and the attention of potential mates. And these all lead to stress, risk-taking, violence, and even homicide.
And while they are typically different, the costs of reproduction paid by women may be even more dramatic than those paid by men. For example, reducing fertility is associated with longer lives and lower rates of obesity in women.
The real value of stopping to consider the lives of Korean Eunuchs who lived hundreds of years ago is to consider the toll that investments in reproduction take on the lives women and men lead today.
Are there less dramatic and more humane ways in which we can moderate the effects of sexual competition and reproduction on lifespans, ageing and quality of life?
Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organization that would benefit from this article, and has no relevant affiliations.