system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why different animals have different lifespans?

I just looked up the average lifespan of a spider (1.5 to 2 years) and I also heard that sharks live for centuries. I was just curious as to why there is such a huge gap.
gpt
There's a concept called the "Hayflick limit", which basically says, a cell can only divide so many times before it loses the ability to. They believe it occurs on the DNA level, a piece is lost each replication, and when enough has been lost, the cell can't reproduce again.

All living creatures are constantly breaking down, and repairing themselves with new cells. When they can't fix the broken parts, they begin to fail, and death is on the way.

The rate the break down/repair happens, and the amount of times a cell can be replaced, varies by animal, resulting in drastically different lifespans.

It's worth mentioning, that in nature, animals (including humans) rarely live to this point. Predators, accidents, sickness, and excessive wear and tear (teeth worn to the point they can't eat, for instance) are generally what causes death. Dying of "old age" requires a very safe environment.