Animals minmax on being active. To the point of going into a damaging overdrive when active and repairs when sleeping. The total accumulated wear is massive. Discarding an old animal and booting a new one seems to be more viable than trying to keep the old one going indefinitely.
Is it really "wear and tear?" or is it an evolved mechanism to keep genetic drift and natural selection alive? Alternatively, it could be an evolved mechanism to avoid genetic bottlenecks caused by highly reproductive individuals over long periods of time.
If John and Mary were first, how long until everyone is a descendent of john and Mary?
Just like an old chat. Start fresh without so much accumulated contextual baggage.
Just like reptiles, who die from the accumulation of damage, at a time depending on the rate of damage, but their point is that mammals don't merely die from accumulation of damage but also have a built-in clock.