Would or have humans’ lifespans increased due to delaying reproduction? I think specifically of the trend in developed countries for people to reproduce later in life, and wonder if, assuming this continues for many generations, their descendents might have an increased lifespan? If so, how many generations are we looking at and would that affect their growth rate and age of maturity?
What would be the mechanism for this longer lifespan? AFAIK, the things that cause us to age and die are unrelated to how old our mothers were when we were born. Human lifespan has increased do to better nutrition, medical care, and other safety measures.
I generally agree with John Mace, but consider that folks who have children late in life survived to late in life. So they’re at least slightly more likely than the general population to have lived at least that long – by definition.
This is a (very weak) selection pressure for longevity, where longevity is equally weakly defined as living to the oldest age one can still have children at. If EVERYONE did this, I can see it extending lifetimes over millenia, albiet slowly even at the rate of evolutionary processes. At the very least, it would increase maximum childbirth ages.
But everyone doesn’t. And since children born to older folks are born at greater intervals than those born to younger folk, the latter will outnumber the former.
Consider we have five “A families” who have children at age 25, and five “B families” who have children at age 50. Let’s also assume that the children have children at the same age as their parents.
After a century, family A will have had five generations. If they started with one monther, and had an average of two children each, that’s a total of 63 people after one hundred years.
Family B, after the same century, will only have 7 people.
So what we have here is a selection pressure that promotes the genes for EARLY childbirth, not later. No matter what percentage (less than 100%) of the population the late breeders make up initially, they’ll eventually be overwhelmed by the numbers of the early breeders.
I would ask even if any effect were limited to a small subset of the population, because I’m interested if it can occur at all…
For the mechanism, it’s definitely not my area, but I’ve read articles saying that changing age at which rats or flies etc. breed will over generations change their lifespan, so that had me wondering if it would apply to humans as well.
Nice analysis, but it assumes that people have children at one age only. What really happens (or happened, before society and birth control) is that people start having children as soon as they are able and continue to have them until they die or get too old. Using that model, there is slight evolutionary pressure on people with the greatest range of ages at which they can have children. If we assume that you can’t push puberty much earlier than it is (I’m not sure that’s a valid assumption), then people who can have kids later in life will slightly out-breed those who can’t.
It would help if you could cite those articles, because I’ve never seen anything along those lines. Of course, IANABiologist, and maybe some of the posters here who are will pop in and give their 2 cents. Sounds fishy to me, though. I have definitely seen rat studies that show reduced calorie diets can lengthen lifespans, but that’s a different thing altoghether.
Not my skillset at all but I wanted to point out that female who have children early are more likely to have MORE children and therefore place the pregancy/childbirth stress on their bodies more often thereby possibly shortening their lives.
Not in the context of the question being asked by the OP-- ie, in modern, industrial societies. Women in these societies tend to control how many kids they have, and pregnancy isn’t much of a risk factor for those women these days. Not to mention the increased level of risk factors for the offspring as women wait longer to reproduce.
Yeah. Not just that, but I assumed they were “point” children (instantaneous in time), that child-producing age was genetic and inheritable, and a whole host of other unlikely things. It’s hard to even start answering hypotheticals like this without a whole bunch of simplifying assumptions, and you’re probably right that I simplified it out of reality.
Turns out, though, that I don’t think we’re answering the OP’s real question, which seems to be whether there’s something about late childbirth, in and of itself, that makes the children more long-lived. To which I can safely say, using all my expertise in this area: “I dunno.” Feel free to ask for a cite on that.