Evolution may explain why women outlive men
A new study suggests that the evolution of menopause plays a key role in women's longer lifespans compared to men. Researchers propose that post-reproductive life in women allows investment in grandchildren, contrasting with men's continued reproduction. This theory draws on data from hunter-gatherer societies and modern populations.
Women outlive men in nearly every country on Earth, with the gap in life expectancy averaging about five years globally and reaching up to seven years in some nations. This disparity has widened in recent decades, particularly since the 1980s, amid improvements in women's health and safety.
Evolutionary biologists from the University of Liverpool, led by Matthew Rogerson, have developed a model to explain this pattern. Published in the Proceedings of the National Academy of Sciences, their work argues that menopause—the cessation of reproduction in women around age 50—enables a prolonged post-reproductive lifespan. 'Our model shows that the evolution of menopause is key to understanding why women live so much longer than men,' Rogerson stated.
The researchers analyzed data from Hadza hunter-gatherers in Tanzania, a group often studied for insights into human evolution. Among the Hadza, women survive to an average age of 70, while men reach about 60. This reflects a broader pattern: in pre-industrial societies, women consistently show longer post-reproductive lives.
In contrast, men continue reproducing into later years, which the model suggests imposes physiological costs that shorten lifespan. 'Reproduction is costly, and in males, it doesn't stop,' explained co-author Virpi Lummaa. The theory posits that women's menopause frees resources for kin support, enhancing inclusive fitness through grandchildren's survival.
The study integrates demographic data from 17th-century Finnish church records and modern global statistics. It challenges previous explanations, like riskier male behaviors, by focusing on biological trade-offs. While the model fits observed patterns, researchers note it requires further testing across species with menopause, such as whales.
This evolutionary perspective highlights how human life history diverges from other primates, where females reproduce until near death. Implications extend to aging research, suggesting menopause's adaptive value beyond fertility.