>> Way too many "other" factors impact post-reproductive longevity... including basic improvements in the social "safety nets"
From an evolutionary perspective, and that of the article, those factors don't matter. A species life expectancy may vary depending on the factors your site, BUT no amount of social safety net can change the *maximum* lifespan.
For most species, being non-productive means the last season of life. Many even die once they have reproduced. So why do humans have such an exceptionally long lifespan? Why is it that we live for so many years after menopause?
The intriguing idea there is so that grandparents can pass on their wisdom to their grandchildren and in the process improve the survival rate of the species. Think about it - Children take care of their parents, and their parents take care of their grandchildren. This cycle has a lot of positives to it which you cannot find in other species.
Are they right? I don't know. But I can imagine that humanity would not be what it is today if older generations could not pass on the benefit of their wisdom to the younger ones.
>> As gene editing technology advances... I don't think you will be able to stop people using it.
Netflix has a new documentary series, "Unnatural Selection." I think you will enjoy it.
>> The latest genetic evidence makes Pritchard think there is an evolutionary trade-off between fertility and longevity...
>> The problem there is sorting out the non-genetic... or already intrinsic... elements in longevity which are less about existing genetic potential... and more about more about how the existing potential is expressed with variation depending on the circumstances.
There is clearly a strong correlation between fertility and longevity. This has been studied extensively in animals. I addition to what I said above, there is a flip side to living past menopause, as in time-to-puberty. It takes humans longer to reach puberty than most species have to live. Intuitively we can sense that if it takes a species a long time to reach puberty, then they need to live longer to survive.
Consider an extreme example of insects vs humans. Insects mature fast and lay thousands of eggs. If they lived as long as humans, there would be no balance in nature. Humans on the other hand take at least 13 - 15 years to procreate (including the gestation time) and normally give birth to only one child at a time. A short lifespan would make us extinct.
But this association has not been fully studied. We know that the more children you have (especially for women) the shorter the lifespan (all other factors being equal). The shortest "optimal" time between births for human female is ~3 years. *If* she is to have them before she is 30, then the theoretical maximum of births per woman is around 5 or 6 kids. |
