Why Women Live Longer Than Men – and Why They Will Continue to Do So

Women live longer than men. This can be observed all over the world, and it has been true throughout history. But why is that, especially now that living conditions have improved in many places and access to medical care is widely available?

The explanation lies with our evolutionary history, and it is so deeply embedded in evolution that neither better living conditions nor medical advances are likely to change it.

These are deeply rooted patterns, which is why we should expect women to continue to outlive men in the future, concludes a team of researchers in a new scientific article published in Science Advances.

The difference between mammals and birds

The lead researchers of the study are Johanna Stärk and Fernando Colchero. Johanna Stärk, who is an evolutionary biologist, was affiliated with the Department of Biology when the research was carried out. Today, she works at the Max Planck Institute for Evolutionary Anthropology in Leipzig. Fernando Colchero is a guest researcher at the Department of Mathematics and Computer Science, specializing in biostatistics and demography,  He is currently the leader of the Statistical Demography Research group at the Max Planck Institute of Evolutionary Anthropology. In addition, 14 other researchers from around the world participated in the study. Link to the study is here. 

The researchers did not only look at the lifespans of men and women. They closely examined lifespan patterns across 1,176 animal species. Among mammals, females live on average 13 percent longer than males. Among birds, however, males live about five percent longer than females – a striking contrast to mammals.

In mammals, there is often intense competition when it comes to finding a mate. In some species, males develop elaborate strategies to attract and monopolize females – whether through bright displays, large body size, or weapons such as horns. All of this comes at a cost.

Evolution has prioritized protecting females

“In our study, we also see that among monogamous mammals – that is, species where males don’t have to compete for mates as in polygamous species – male lifespan increases, so the gap becomes smaller,” explains Johanna Stärk.

The research team also points out that evolution may have prioritized protecting mammalian females, since they are typically the ones responsible for raising offspring.

“There should be a selective advantage for females to survive until their young can fend for themselves or reach sexual maturity, particularly in long lived species such as primates” says Stärk.

Is it the same in zoos?

But what happens if you remove the stress factors of life in the wild? What if there are no predators, diseases, hunger, or extreme weather? How do mammals fare in a zoo?

“The removal of stress factors can make a difference, but it does not erase the lifespan gap. The difference is somewhat smaller, but still there. Even in zoos, female mammals live longer than males. We therefore believe that differences in mammalian lifespans are not just the result of environmental factors, but also biological ones rooted in our evolutionary history. And that suggests that the gap might persist, even as living conditions improve,” says Stärk.

Birds are much more often monogamous, which means there is less competition among males. As a result, it is not unusual for males to outlive females. But when researchers looked at polygamous bird species, they found that the gap between males and females is substantially reduced.