Being immortal means you never have to take Philosophy in JuCo.
Evolutionarily speaking there is a bit of pressure to live a bit past childbearing age, as our children require more training and assistance than any other animal child. Having parents and even grandparents stick around a bit longer helps grow our communities and gives a greater chance for knowledge and skills to be passed down.
But yeah, we age because, almost by definition, there really can be no evolutionary pressure to become immortal.
Does that mean that sociopaths live forever?
This is why people shouldn’t try to adjust their meds without consulting their doctor.
There is evolutionary pressure to live longer. If Ann’s children have a freak mutation that they never age, then they are not only likely to survive much longer than Bob’s, ordinary, children, but her children can keep squirting out kids of their own indefinitely.
How species arrive at their finite lifespan is not only a function of how long their infancy is, it’s also partly a function of what their life expectancy assuming a healthy body is. Basically if the niche your species exploits means that few would make it to 10 years old, even without ageing, then genes whose effects are not detrimental until year 10 are not selected out of the genepool (and may even be selected for if they have positive effects prior to that kind of age).
I’m a bit uncomfortable with the way this thread started as metaphysics, but then we’re now talking about real species and why they aren’t immortal.
Immortality in the sense of the OP, where we can’t die, is not something that could happen in our universe.
Living indefinitely however, *is *something physically possible. And indeed there are a few species that display what we call negligible senescence.