Scientists discover that castrated animals live up to 20% longer

There's a widespread belief that reproduction is always and in every case a sign of vitality. However, when we look at what happens in nature, the picture becomes more complex.

According to a new scientific study published in Nature, in many species, forgoing reproduction is associated with a longer lifespan. This is a recurring finding, which appears in very different contexts and concerns mammals, fish, reptiles and even humans.

By comparing fertile animals with sterilized or hormone-controlled ones, researchers have found that non-breeding specimens tend to live longer, in some cases up to 20% longer.

When reproduction stops, the body seems to age more slowly

From a biological point of view, reproduction represents a 'considerable investment'. It involves hormone production, pregnancy, lactation, competition with other individuals and defense of resources. A colossal amount of energy is deployed and diverted from other fundamental processes such as cellular repair and maintenance of internal equilibrium.

By analyzing data from over a hundred species kept in zoos and aquariums, as well as dozens of previous studies, researchers observed that spayed or neutered animals have a longer life expectancy than those that continue to reproduce. This effect is even more obvious in harsh environments, where the organism has to make drastic choices regarding the use of its resources.

Men and women: two different paths to longer life

However, the benefits are not the same for everyone. For men, the key factor is above all hormonal. The study clearly shows that simply blocking fertility is not enough: vasectomy, for example, does not significantly alter lifespan. Castration, which stops the production of sex hormones, is another matter.

In male animals deprived of testosterone, aggressive behavior and the risk of dying in confrontations or fights are also reduced. Less competition, less exposure to unnecessary danger. When intervention takes place before sexual maturity, the effect on longevity is even more marked.

For females, on the other hand, the advantage comes mainly from avoiding the costs associated with pregnancy and lactation. These processes strain the immune system and increase vulnerability to infection. By stopping reproduction, the risk of death from infectious disease is reduced, and aging seems to be more gradual.

What does all this have to do with humans?

The authors of the study point out that these mechanisms are not far removed from the human experience. We share the same physiological foundations as the other species analyzed. Women, for example, live longer on average than men, and menopause marks the natural end of the reproductive phase.

According to the researchers, ceasing to reproduce could have represented an evolutionary advantage, enabling greater survival in the final stages of life. Some historical data on castrated men (eunuchs) also point in this direction, showing a longer lifespan than their peers.

Of course, this does not mean that giving up reproduction is the 'solution' to living longer. But this study does remind us of something fundamental: in nature, every choice has a cost. Reproduction guarantees the future of the species, but does not always coincide with the greatest benefit for the individual. And this tension between survival and continuity seems to run through all life on Earth.

Source : Nature

(MP/©GreenMe.it/Translation and adaptation: The Global Nature/Pic: Unsplash)