system
Given the following post, respond as if you're commenting on Reddit:
human
What determines the lifespan of a species?

Why is it that humans can live up to 100, but dogs have an average lifespan of 10 years, and flies/insects only live a couple of days? What determines it? Is it the enviroment or something to do with the animal's anatomy? Would we be able to increase other animals' lifespans like we did with our own?
gpt
It's a combination of factors. Over long periods evolution selects for traits that improve chances of survival to adulthood and reproductive success, which often doesn't promote longevity. Because humans require a relatively long time to reach sexual maturity, keep learning throughout our lifetime and live in social groups benefiting from members surviving long past their reproductive phase evolution favours traits improving our longetivity. So that explains why different species developed such different lifespans.

What limits a species lifespan in pratice varies wildly between species. Some insects lose their digestive system when reaching sexual maturity for example, so their bodies simply run out of resources causing them to die. Dogs on the other hand are mainly limited by genetic instability. Dogs annually lose approximately 3.3% of the DNA in their heart muscle cells while humans lose approximately 0.6% of their heart muscle DNA each year for example. They often die because their body has degraded to a point where they're no longer able to find food. While humans (in nature) often die from infection or disease.

Humans have extended their average lifespan vastly by simply getting better at preventing things from killing us. Using the same approach we can extend average lifespans for dogs a little while it doesn't improve the lifespan of these insects at all.

We don't understand aging good enough at this time to tell how much more we can extend our average lifespan, but probably with at least a few decades. Beyond that we'll need capabilities for repairing permanent damage to our DNA, with which we can extend the life of dogs as well, or genetic manipulation which even enable us to let those insects live longer by hacking a degistive system into their adult bodies.