|MadSci Network: Evolution|
Watcha know Joe?
Paleontologists and Paleozoologists have used the technique of physical and cultural comparison to determine such things. What that means is that they assume that creatures of similar size and biology live lives of similar length and nature. They extrapolate that a dinosaur twice the size of an elephant might live one and a half to two times as long as an elephant. So basically, the larger an animal is, the longer and slower it lives it's life. The smaller: the faster and quicker they live their lives. Also, the smaller the brain size, the quicker they mature to adulthood and the sooner they reproduce. There are some other factors but that is the quick and easy answer.
Thanks for the cool question,
Try the links in the MadSci Library for more information on Evolution.