Yet women have a longer lifespan despite shorter reproductive years.
If in a hunter-gatherer society most people stop reproducing after 40 (not entirely realistic, but bear with me), me being alive and fit at 45 can still improve the survival of my genepool. I can hunt meat and gather plants to make sure my children and grand-children are well-fed and able to produce plenty of offspring, carrying my genes on. I can build shelter, care for the young (improving their survival chances and freeing up the parents to do more physically demanding work).
And my siblings share half of my genes, and my cousins a quarter (assuming no inbreeding at all, otherwise the numbers go up). So helping their children survive and proliferate is a win for the proliferation of my genes. Evolution gets less effective the more indirect the effect and the lower the gene contribution, but it doesn't completely stop working. If there is one clan where everyone dies at 30 and one where people stop reproducing at 30 but stay useful members of society until 60 then then the second clan will do better and outcompete the first
But you also take up resources, continue to decline physically, etc.
We know that there is strong selection pressure for things that occur during reproductive years. No one debates this.
How much the sort of scenarios you're discussing impact selection pressure is significantly less clear.
But it's also a moot point for this discussion - we haven't been in a world where people can get this fat so easily and in such large quantities for long enough to make significant impact to evolution even if we assumed that selection pressure works the same in said world - and again, we know it doesn't.
Grandparents are a selective advantage well after reproduction. Older members of the tribe can watch the young while fitter members engage in hunting and foraging. They can also teach the young. Most tribes around the world that still exist you see this pattern.
Correlation is not causation. Plenty of people theorize there is large selective advantage here, sure. They may even be correct! Others disagree with them on it being a large advantage.
But even if there is it doesn't mean that there is any reason whatsoever that increased GLP-1 production would be enough of an advantage to have had significant impact on evolution. We're going from A is true, B is likely true, C might maybe be true, all the way to Z is definitely true.
> Yet women have a longer lifespan despite shorter reproductive years.
After industrialized nations have reduced both maternal mortality and violent death (warfare) to small fractions of their pre-modern levels. The life tables of 1500, 500, or 5000 BC would look very different than their modern versions.
If in a hunter-gatherer society most people stop reproducing after 40 (not entirely realistic, but bear with me), me being alive and fit at 45 can still improve the survival of my genepool. I can hunt meat and gather plants to make sure my children and grand-children are well-fed and able to produce plenty of offspring, carrying my genes on. I can build shelter, care for the young (improving their survival chances and freeing up the parents to do more physically demanding work).
And my siblings share half of my genes, and my cousins a quarter (assuming no inbreeding at all, otherwise the numbers go up). So helping their children survive and proliferate is a win for the proliferation of my genes. Evolution gets less effective the more indirect the effect and the lower the gene contribution, but it doesn't completely stop working. If there is one clan where everyone dies at 30 and one where people stop reproducing at 30 but stay useful members of society until 60 then then the second clan will do better and outcompete the first