Eli5: how do scientists “know” the behavior of dinosaurs without actually observing them?

Question

Eli5: how do scientists “know” the behavior of dinosaurs without actually observing them?

In: Biology

Answer 1

We assume from circumstantial data:

* There’s such a thing as [convergent evolution](https://en.wikipedia.org/wiki/Convergent_evolution): animals that do similar things tend to evolve similar appearances, no matter how much genetic difference and time has passed between them. So we can estimate things for dinosaurs that resemble modern animals.
* Similarly to how forensic experts determine circumstances of a crime from seemingly unrelated data, so we can do with fossils. Analysis of stomach and nest contents, poop, etc. can show how an animal lived and what it ate. We can compare bite marks on bones to teeth of known animals to see what exactly killed it. And so on.