Why do dogs age faster and there life span is shorter than humans?

Question

Why do dogs age faster and there life span is shorter than humans?

Answer 1

Dogs are just designed that way.

Many animals go through their life cycle very quickly.

Ecologists might say it means that they have a better chance of adapting to their environment. But then why do some plants live for hundreds of years?

Answer 2

because nature has designed them so... !!! But creatures with a slower heart rate have a longer life span e.g. elephant,and with faster heart rate have a shorter life span

Answer 3

I remember from Biochemistry II that humans turn spent heme molecules into bilirubin, whereas in most animals the breakdown stops one step before. Bilirubin is costly to produce, but it is an antioxydant and allows us to live longer.

I don't know whether other long-living mammals, such as elephants, produce it. However, since their diet is exclusively vegetarian, they have ampler access to plant antioxydants than dogs.