Question: why do most pets not live longer than humans?

Verity Hill answered on 13 Nov 2018:

ooo see this is a really fun question! Part of evolutionary biology is understanding why different animals live for different lengths.
Most of it is to do with how quickly they reproduce. All living things have a limited amount of energy to put into different things. You can put this energy into reproducing, or into surviving for longer. If you think of very long lived species like humans or elephants, we don’t have many babies, and each one takes longer to grow up. If you think of shorter lived ones, like mice, they have lots!
This is also tied into size – if you want to put energy into having babies faster, you have less time to grow bigger. So it also happens that animals that don’t have many babies tend to be bigger (like us, elephants, rhinos, gorillas) than ones that do (mice, shrews, cats).
Realistically, you want most pets to be small right? So they can live comfortably in your house. So most pets are animals that have chosen the “live fast, die young” strategy of not being that big, having lots of babies and then dying earlier.