SATURDAY, 27 OCTOBER 2007We all know that women tend to outlive men. Current life expectancies for the United Kingdom stand at 81 and 77 respectively, a significant discrepancy. Scientists have long struggled to understand why. Theories range from damaging effects of the male hormone testosterone on the body to evolutionary advantages to the species by easing the pressure on scarce resources such as food and breeding sites.
Professor Tim Clutton-Brock and Dr Kavita Isvaran, of the Large Animal Resarch Group (LARG), based at the Department of Zoology, think they have found the answer. When they looked at information about breeding habits and life expectancies of various species they found that on balance, more polygamous species showed greater differences in lifespan and breeding periods between the sexes.
Take, for example, red deer. Each autumn, mighty stags battle it out to get a chance to mate. Only the strongest, most successful stags gain control of a harem. For this purpose, they expend large quantities of energy building up their antlers and thick necks. So evolution has favoured the development of these characteristics, but has compromised on a lifespan of only 75 per cent that of female deer. Similar results were seen in lions and elephant seals.
In comparison, when looking at monogamous species such as meerkats, the researchers found differences in life expectancy between the genders were much less marked.
Human parallels can certainly be drawn from these results. Men do compete with each other for the attention of women, and expend time and energy in doing so. Men also generally do live for fewer years than women. In light of the new findings, it makes sense to link these two facts.
Written by Katy Horder
(Article written for Varsity Science, and republished with permission)