Why do women live longer than men?
Why do women live longer than men on average? What's the mechanism behind it?
Chris Smith put this question from Jim to physiologist, Sam Virtue. Plus, psychologist Helen Keyes is all too familiar with the risky business between genders.
Sam- Okay so that’s a good question and quite a big question because it’s not just men and women. It’s loads and loads of different animals throughout the animal kingdom, down to insects.
Chris - Where you see a sex bias? Where you will see a female bias?
Sam - Mostly it’s biased towards females living longer but there are some reversals and somewhere you don't have a bias. What it comes down to largely is that in many species, males and females have very different requirements in terms of how much effort they put into producing children essentially. In many species, males will mate and then disappear off whereas females will then have to produce the baby. For men, the optimum is to essentially mate with as many females as possible whereas for females you want to be picky about your mate because you invest a lot into that baby.
Chris - But if I could challenge that because that's all very well, you’re reproducing when you're young but we’re talking about people living a long time. Many many species don’t reproduce when they become old, including humans, so there must be something else which is driving the persistence of these older females in the population.
Sam - This seems to be quite a majorly human thing. That this sort of ageing aspect to it, in terms of the menopause in particular, being so far removed from when we die. A lot of species it will be a lot closer. Why that's occurred is a very good question and interestingly one of the hypotheses has actually been to do with the way human structures have built up. Favouring, bizarrely enough, the idea of men becoming more attractive and more suitable as mates as they age which has actually put a drive on male longevity.
Chris - Is that just wishful thinking?
Sam - It’s called the “Patriarchy Hypothesis” which then has dragged up the whole lifespan of both men and women. But then we have a bizarre question; why aren't the men longer lived than the women? And so then a flipside comes that males’ secondary sexual characteristics and tendencies towards violence and risk seeking behaviour, to try and compete for these mates, drive down their age. The two things combine.
Chris - If you look at conceptuses, the number of babies being conceived, there's a slight bias towards more male babies are conceived but then about the equivalent numbers of male and female babies are born. Then after that pretty much there’s an excess of females for ever.
Sam - If you say so, I’m not aware of that one.
Chris - It's an interesting figures that we see. It seems like there's this bias, initially in favour of males, in order perhaps to counteract the very thing you say, which is that males more risk prone. So who knows!? Helen, a lot of this must chime with your research on cars and driving and that kind of thing.
Helen - It does and I know from risk taking behaviour studies there is obviously a big difference between risk taking behaviour in young men and young women but this risk really decreases in older drivers as we get older. It can’t fully account for the difference in life expectancy between men and women. Although it does input into it. But as a psychologist, I think something really interesting to me is the protective factors of socialisation as we get older. Socialising with people protects you against all sorts of things, like Alzheimer's and dementias, but also of death itself. It adds years to your life. We know that that older women are more likely to have a greater social networking a richer social network than older males and I think this might feed into this longer life expectancy.