I'm pretty skeptical of this idea. I would almost expect the opposite, that if you're not exercising than you're likely not contributing to the group so your offspring has a better chance of survival if you die. We know ancient humans often took care of their elderly well beyond the point of being able to physically assist with daily tasks so I would almost expect this to be an end of life marker than anything to do with resource scarcity.
Also, I think studies of poverty show generally show that resource scarcity is almost always worse for health outcomes. Resource over-abundance is maybe also damaging but the idea that being resource scarce is beneficial for longevity because you need longer to mate seems almost certainly false to me.
Also, I think studies of poverty show generally show that resource scarcity is almost always worse for health outcomes. Resource over-abundance is maybe also damaging but the idea that being resource scarce is beneficial for longevity because you need longer to mate seems almost certainly false to me.