We know larger animals tend to have longer lifespans. But why do big cats(like leopards, etc)have such a short life(about 15 years) compared to humans(about 80 years)?

Question

p.s.Big cats and humans have similar body weights, if not higher.

In: Biology

Answer 1

Because they don’t need to live that long.

The only “goal” evolution has (if it can be said to have a goal at all) is to pass on genetic material. Every selective pressure is focused on this one event. Once you have passed on sufficient genetic material to more or less guarantee a third generation, then you become nothing more than a useless consumer of the resources that your progeny needs.

There are a lot of very different strategies based on this principle. For example, there’s the “shotgun” approach; have has many babies as possible but provide no parental care. Most babies will die this way, but from sheer numbers, a few will survive to reproduce. Opposite that is the “sniper” approach; have one or a few children, then spend a lot of resources on their development to adulthood. These are known as the “r/K selection theorem”. This is a spectrum, so there are a lot of species in between these two extremes.

Humans are on this spectrum at the extreme K end. Not only do we invest vast resources over many years to get our very few children to adulthood, we’ll even stick around to ensure their own reproductive success (menopause has been hypothesized to be part of this; pilot whale males with menopausal mothers in the pod have more reproductive success than males without). Cats are at the K end as well, but not nearly as extreme as we are. They provide enough parental care to a few litters to ensure grandkids, then pop off.

Other selective pressures focus on the individual’s ability to survive after parental care. Humans rely on a large brain for this, while cats rely on muscles and claws. Thanks to our brains, humans take *way* longer to reach sexual maturity than cats do. This means that even if a human didn’t live much past seeing grandkids, that would still mean a lifespan 3-4x that of cats.

In short, lifespans correlate more with time to the third generation than to size of the adult organism. It’s still not a very strong correlation, as there are many exceptions to the trend.