Credit: George Hodan/public domain Across the entire world, women can expect to live longer than men. But why does this occur, and was this always the case? 
 
 According to a new study led by University of Southern California Leonard Davis School of Gerontology researchers, significant differences in life expectancies between the sexes first emerged as recently as the turn of the 20th century. As infectious disease prevention, improved diets and other positive health behaviors were adopted by people born during the 1800s and early 1900s, death rates plummeted, but women began reaping the longevity benefits at a much faster rate. 
 
 In the wake of this massive but uneven decrease in mortality, a review of global data points to heart disease as the culprit behind most of the excess deaths documented in adult men, said USC University Professor and AARP Professor of Gerontology Eileen Crimmins. 
 
 "We were surprised at how the divergence in mortality between men and women, which originated as early as 1870, was concentrated in the 50 to 70 age range and faded out sharply after age 80," Crimmins said. 
 
 The study was conducted with USC University Professor and ARCO/William F. Kieschnick Professor in the Neurobiology of Aging Caleb Finch and Research Associate Hiram Beltrán-Sánchez of the Center for Demography of Health and Aging at the University of Wisconsin-Madison. It examined the lifespans of people born between 1800 and 1935 in 13 developed nations. 
 
 Focusing on mortality in adults over the age of 40, the team found that in individuals born after 1880, female death rates decreased 70 percent faster than those of males. Even when the researchers controlled for smoking-related illnesses, cardiovascular disease appeared to still be the cause of the vast majority of excess deaths in adult men over 40 for the same time period. Surprisingly, smoking accounted for only 30 percent of the difference in mortality between the sexes after 1890, Crimmins said. 
 
 The uneven impact of cardiovascular illness-related deaths on men, especially during middle and early older age, raises the question of whether men and women face different heart disease risks due to inherent biological risks and/or protective factors at different points in their lives, Finch said. 
 
 "Further study could include analysis of diet and exercise activity differences between countries, deeper examination of genetics and biological vulnerability between sexes at the cell level, and the relationship of these findings to brain health at later ages," he said. 
 
 The study, "Twentieth century surge of excess adult male mortality," appears in the Proceedings of the National Academy of Sciences and was supported by the National Institute on Aging. 
 
 Explore further: Women with type 1 diabetes at significantly higher risk of dying compared with men 
 
 More information: Twentieth century surge of excess adult male mortality, www.pnas.org/cgi/doi/10.1073/pnas.1421942112 ||||| Fountain of youth: Not only is she likely to live longer than he does, but she will help him live longer, too. Image: KENDRICK BRINSON Luceo The Best Science Writing Online 2012 Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way... 
 
 
 
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 If there are any men left who still believe that women are the weaker sex, it is long past time for them to think again. With respect to that most essential proof of robustness—the power to stay alive—women are tougher than men from birth through to extreme old age. The average man may run a 100-meter race faster than the average woman and lift heavier weights. But nowadays women outlive men by about five to six years. By age 85 there are roughly six women to every four men. At age 100 the ratio is more than two to one. And by age 122—the current world record for human longevity—the score stands at one-nil in favor of women. 
 
 So why do women live longer than men? One idea is that men drive themselves to an early grave with all the hardship and stress of their working lives. If this were so, however, then in these days of greater gender equality, you might expect the mortality gap would vanish or at least diminish. Yet there is little evidence that this is happening. Women today still outlive men by about as much as their stay-at-home mothers outlived their office-going fathers a generation ago. Furthermore, who truly believes that men’s work lives back then were so much more damaging to their health than women’s home lives? Just think about the stresses and strains that have always existed in the traditional roles of women: a woman’s life in a typical household can be just as hard as a man’s. Indeed, statistically speaking, men get a much better deal out of marriage than their wives—married men tend to live many years longer than single men, whereas married women live only a little bit longer than single women. So who actually has the easier life? 
 
 It might be that women live longer because they develop healthier habits than men—for example, smoking and drinking less and choosing a better diet. But the number of women who smoke is growing and plenty of others drink and eat unhealthy foods. In any case, if women are so healthy, why is it that despite their longer lives, women spend more years of old age in poor health than men do? The lifestyle argument therefore does not answer the question either. 
 
 As an experimental gerontologist, I approach this issue from a wider biological perspective, by looking at other animals. It turns out that the females of most species live longer than the males. This phenomenon suggests that the explanation for the difference within humans might lie deep in our biology. 
 
 Many scientists believe that the aging process is caused by the gradual buildup of a huge number of individually tiny faults—some damage to a DNA strand here, a deranged protein molecule there, and so on. This degenerative buildup means that the length of our lives is regulated by the balance between how fast new damage strikes our cells and how efficiently this damage is corrected. The body’s mechanisms to maintain and repair our cells are wonderfully effective—which is why we live as long as we do—but these mechanisms are not perfect. Some of the damage passes unrepaired and accumulates as the days, months and years pass by. We age because our bodies keep making mistakes. 
 
 We might well ask why our bodies do not repair themselves better. Actually we probably could fix damage better than we do already. In theory at least, we might even do it well enough to live forever. The reason we do not, I believe, is because it would have cost more energy than it was worth when our aging process evolved long ago, when our hunter-gatherer ancestors faced a constant struggle against hunger. Under the pressure of natural selection to make the best use of scarce energy supplies, our species gave higher priority to growing and reproducing than to living forever. Our genes treated the body as a short-term vehicle, to be maintained well enough to grow and reproduce, but not worth a greater investment in durability when the chance of dying an accidental death was so great. In other words, genes are immortal, but the body—what the Greeks called soma—is disposable. ||||| Why women live longer than men: Male bodies are much more genetically 'disposable' 
 
 
 
 It is the ultimate battle of the sexes - and women usually win. 
 
 Now scientists have come up with a new theory for why woman live, on average, longer than men: men are more biologically ‘disposable’. 
 
 The controversial theory, developed by Professor Tom Kirkwood of the University of Newcastle, suggests that the female body is better at carrying out routine maintenance and keeping the body’s cells alive. 
 
 A British man who has reached 65 can expect to live another 17.6 years - women get a further 20.2 years 
 
 Professor Kirkwood believes there is now growing evidence to suggest that men are more disposable than women, because the cells of their bodies are not genetically programmed to last as long as they are in females. 
 
 Many scientists believe that the aging process is caused by tiny faults throughout our body. As the tiny faults build up the length of our lives is determined by how quickly our body is able to carry out running repairs. 
 
 As the cells miss opportunities to repair themselves our body gradually degrades until we eventually die. 
 
 Professor Kirkwood’s theory behind why our cells do not mend every tiny problem in our body is that it is built into our DNA. The reason we do not live forever is because it would have cost our hunter-gather ancestors too much energy to constantly replenish cells when hunger was a more immediate danger, he says. 
 
 Life expectancy for other animals 
 
 Chimpanzee 
 
 
 
 Male: 45 years 
 
 Female: 59 years Killer whale 
 
 
 
 Male: 50-60 years 
 
 Female: 90 years 
 
 
 
 Mosquito 
 
 Male: 1 week 
 
 Female: 1 month 
 
 Sea lion 
 
 Male: 18 years 
 
 Female: 30 years 
 
 
 
 ‘Under the pressure of natural selection to make the best use of scarce energy supplies, our species gave higher priority to growing and reproducing than to living forever.,’ he writes in the magazine American Scientist. 
 
 ‘Our genes treated the body as a short-term vehicle, to be maintained well enough to grow and reproduce, but not worth a greater investment in durability when the chance of dying an accidental death was so great.’ 
 
 This theory’s next logical step would suggest that women live longer because their bodies are less disposable than those of men, it makes more sense for the cells to put in more effort to correct any laws in the DNA, for example. 
 
 This makes sense on purely reproductive grounds, Professor Kirkwood argues. 
 
 'In humans, as in most animal species, the state of the female body is very important for the success of reproduction', he writes. 
 
 ‘The foetus needs to grow inside the mother’s womb, and the infant needs to suckle at her breast. So if the female animal’s body is too much weakened by damage, there is a real threat to her chances of making healthy offspring. The man’s reproductive role, on the other hand, is less directly dependent on his continued good health.’ 
 
 In the past scientists had suggested that the fact a man’s working life was more demanding could have accounted for their shorter lives. 
 
 But although life expectancy has risen steadily in Britain over recent decades the narrowing gender equality gap has seen no corresponding narrowing of the life expectancy gap between men and women. 
 
 An ONS graph showing how average life expectancy has risen over the past 20 years 
 
 Professor Kirkwood has carried out research that shows that females in most animal species live longer than males. Studies have also shown that neutered animals live longer and castrated men also live longer than normal men 
 
 Professor Kirkwood told The Independent: ‘In females, reproductive success is so inextricably bound up with the integrity of the body and the evidence is really clear right across the life course – men have a statistically significant, higher likelihood of dying at all ages compared to women. 
 
 'It seems to be deeply engrained in the biology. Obviously differences in lifestyle may add or subtract to it, but I'm absolutely convinced that there's an underlying biological explanation for the gender differences we see between the life expectancy of the sexes.'
– There's a reason we don't typically call Earth's oldest person the oldest woman in the world—the oldest person is pretty much always a woman. In fact, just two of the world's 53 living supercentenarians (people 110 and older) are men, reports IFL Science. But why is the longevity gap so stark, and how long has it been so? An international team of researchers is investigating the lifespans of men and women born between 1800 and 1935 in 13 developed nations in search of answers, reports PhysOrg, and they've found that women's superior longevity only emerged recently. Before 1840, death rates were very similar between men and women. But since those rates began to plummet in 1880 thanks in large part to improved diets, vaccinations, and better health care, female death rates have dropped 70% faster than male ones, and heart disease seems to be holding men back the most, the researchers report in Proceedings of the National Academy of Sciences. Men may be more biologically susceptible to cardiovascular health problems, and their different weight distribution could play a role here, reports Live Science. The researchers plan to further explore the differences between male and female biology, genetics, and lifestyles to look for answers. (The oldest man in the US says his trick has been to enjoy a can of beer a day.)