Lately there has been some debate between Dr. bloggers questioning whether evolution selects more for reproduction or longevtiy and its impact on the optimum diet. Some have stated that evolution selects for reproduction not longevity because genes don't care about living past their reproduction, so to speak. Others have argued that evolution may select for longevity because of the contribution of people beyond child bearing years to feeding and educating children.
This http://www.sciencedaily.com/releases/2012/10/121023204142.htm is an interesting simulation of the impact of grandmothers on reproduction and evolution. The simulation seems to indicate that humans may have significantly longer post-childbearing lifespans, than other primates, because of grandmother's help in feeding children post-weaning, allowing younger women to have more children. By allowing mothers to have more children the odds of early women with long longevity passing on their genetic advantage was increased.
I believe that there is was selection pressure for longevity.
What do you guys think of the grandmother hypothesis? Does it make you think about changing your diet at all? How?
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Personally I am solidly in the reproductive adaptation camp.
However, I thought that the grandmother hypothesis was about menopause. And that the evolutionary advantage of menopause was to prevent women from outlasting their offspring. Human "grow up" pretty slowly. So if a woman had a lifespan of say 50, and had a child at 45, that child would not be self sufficient at the time the mother passed away. So the grandmother hypothesis states that women have menopause to prevent them from outlasting their offspring which correlates to approximately the amount of time it takes for early offspring to reproduce.
This is a very interesting twist on the Grandmother hypothesis.
I think it makes a lot of sense. I was reading something the other day about why human females have menopause at all, which is pretty much unheard of in any other species, in which fertility span equals lifespan. Humans are particularly complex and it seems like a much greater advantage to have an older female not preoccupied with continual pregnancy and child-rearing.
I definitely don't buy the story that women reach menopause because humans didn't generally live past 40.
And, being a socially complex species, I think looking at evolution from a 'survival of the fittest' perspective is overly simplistic. We are much more than individual gene-sacks trying to knock off as many copies as possible. We survive and evolve as a group, and there are other driving forces behind genetic adaptation. That's why 'longevity vs reproduction' is a non-argument, the way I see it, as they are not opposing forces.
How it might affect my diet decisions? As a 33 year old VERY premenopausal woman with a teenaged daughter, I'll try to refrain from eating her potential babies. But I'm too young to be 'gathering tubers' for the little brats.:p
I think there is merit to the grandmother theory of longevity. It may be harder for us to understand it since many of us come from cultures where the older generations are not considered valuable. There are teratogenic effects to offspring that don't show up until the 3rd generation. So having wisdom to pass through multiple generations can mitigate this effect. We're kind of seeing the opposite of that nowadays as people grow up without the wisdom of their elders and instead get their information from advertising. Many people believe that the current youngest generation will struggle more than any other to reproduce and it may be quite possible that within a generation or two, there was be a crisis of reproduction ability among many people, with some not being able to conceive or carry to term or with very sick offspring from multiple teratogenic effects.
I think it's fairly well known that the maximum lifespan of primate females tends to be longer than males in species where the females have disproportionate caregiving duties, and primate males and females tend to live equally long in species where they tend to equally share childrearing duties. Perhaps childrearing in primates, including humans, is important. Shocker. And human lifespans are particularly long, and achievable not just with modern medicine but also with reasonable frequency in hunter-gather societies, so it seems as if there's value to keeping the old folks, especially old women, around. Whether it's to feed their grandchildren or because they remember where water could be obtained during that long-ago drought or whatever, it's clearly not the case that primal/paleo eating is only good to keep you going through age 35.