system
Given the following post, respond as if you're commenting on Reddit:
human
What determines life expectancy in a lifeform?

Yesterday I visited my neighbor and he introduced me to his parrot. a smart grey fella with a red chest. my neighbor then told me he was 77 years old. I thought it was freaky that this bird has lived this long and I started googling average life expectancies of animals, and they seem ... completely random?! So I wanted to ask, is there any science behind why some animals live longer and some don't and could you explain?
gpt
In mammals it's somewhat proportional to the resting heartbeat and metabolic rate. Even though they can be vastly different sizes, they all get about a billion heartbeats. Live fast, die young in action. Humans do a bit better, about 4 billion.

Different families of creature don't necessarily fit.