New study: Males might be more "disposable" than females

Posted by David Gomez

Scientists may have recently figured out why women tend to live longer than men. A new study set to be published this month in Scientific American says that males could be genetically more disposable than females.

People used to think that women lived longer because men traditionally have more stressful working lives than men. But this has been shown to not be true since women have begun to work in most of the same jobs men do, yet the age gap between them has not evened out.

Another belief is that women live longer because they are less likely to have bad habits like boozing it up, chain-smoking, and eating junk food. The problem with this theory is that, while women do tend to live longer than men, they are usually less healthy in old age than men of the same age.
 
A further problem with this idea is that the females of most other species similarly live longer than males. And other species of animals don’t get to booze, smoke, or eat snacky cakes, unless they have very mean and very bored owners.

It is a pretty widely accepted theory that our bodies age due to a slow buildup of damage to cells or cellular components like protein or DNA. The deteriorating build-up occurs because the body’s regenerative process is not perfect, and some of the body’s damage remains unrepaired.

Professor Thomas Kirkwood, director of the Institute for Ageing and Health at Newcastle in England, proposed in 1977 that our bodies do not repair themselves as well as they could because natural selection favors the growth and procreation phases of life over older age, essentially viewing the body as a temporary vehicle for passing on the genes to the next generation and not worth the energy investment in keeping itself healthy in old age.

Kirkwood dubbed this the disposable soma theory (soma being Greek for body). In his article to be published this month in Scientific American, Kirkwood broadens his theory to explain the permanence gap.

Kirkwood’s research has shown that animals that live long have more capable body maintenance systems than animals that have short lives, and that long-living animals are apt to be larger, more intelligent, or have some defense mechanism like flight that allows them to grow old and prosper.

For long-living animals it seems that their bodies are less disposable and the effort their bodies put into repairing itself is quite beneficial. This led Kirkwood to the idea that males have shorter lives than females in most species because they are genetically more disposable.

Lab studies have also shown cells in female rodents fix damage better than in males, but this changes when the ovaries are surgically removed. It is also understood that castrated male animals live longer than intact animals. If you call being castrated “living”.

According to a Physorg.com story, Kirkwood said there is also evidence from an institution for the mentally disturbed in Kansas, where castration of male inmates was once a common practice, that castrated men lived an average of 14 years longer than uncastrated inmates.

Females need healthier bodies because they have a greater role in nurturing their young into adulthood. Males have a lesser role that is not related to a long life.

In fact, high testosterone levels actually seem to shorten the lifespan. So being a potent, manly man is not the key to a long life if you are a male.

Professor Kirkwood also said on Physorg.com that while it's "difficult to say things with absolute assurance" he is confident his theory of males being more "disposable" than females is the underlying biological explanation for the greater longevity of females.