Eli5: how do scientists “know” the behavior of dinosaurs without actually observing them?
In: Biology
There is some guesswork, but they can compare the bones to living animals (things like what shape the teeth are), they can look at bone thickness to work out how they moved, injuries to work out if they fought or which species preyed on which, sometimes dinosaurs even die in the middle of fighting so we can learn a lot about how they attack it defend themselves etc.
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.
Sometimes we find fossils that suggest behaviour.
The first example of Oviraptor, for example, was found with some fossilised eggs which seemed to belong to another species. The paeleontologists who found it interpreted that find as *eating* eggs – they named it Oviraptor because that name means “egg thief”. They thought it was stealing eggs from another species for food.
We find stuff that suggests the diet of different species. We find stuff that suggests mating behaviour, or parental behaviour; for example, if paeleontologists find an adult dinosaur with a half grown juvenile…that suggests the adult delivered some level of care to their offspring, and the offspring stayed with them. We find stuff that suggests various relationships between different species.
The fossils tell us something about what the living creature was like. We just have to figure out what.
As with most things, scientific examination is knowledge without absolute certainty. We examine data (which is real, grounded, observable) and make our best guesses to explain that data.
In the case of dinosaurs, we have three useful tools:
* Ecological niches are not going to radically change. You need primary food sources that generate their own food (read: plants, fungi, bacteria, etc.) from raw materials in the world, and then herbivores that eat those things, and then carnivores that eat *those* things, etc. This means we can make very good guesses just by comparing fossils to creatures that we know and can directly observe.
* Some fossils show physical wear and tear or injury which shows stuff about how they lived. E.g. dinosaurs with large, flat, worn-down teeth were *probably* herbivores. Dinosaurs with large, sharp, cutting teeth were *probably* carnivores. Etc.
* A few, rare, fossils contain *stomach content* fossils, which lets us see what they ate, or are things like amber or whatever that can preserve structures that would normally not be fossilized. Likewise, some rare fossils are a predator that died as it was eating its prey, so we get to see what those looked like; or a nest being tended to by a parent; etc. These are physical records that reflect behaviors.
There’s a golden rule in biology, “Form Follows Function”, if an organism has sharp teeth, we can infer its carnivorous because sharp teeth are useful for meat but awful for vegetation. Similarly, keeled sternums are often indicative of flight due to needing the extra surface area for an attachment point of flight muscles.
Basically they look at bones and such, put a million pieces together and get an overall estimate of its niche.
Watch the show Bones. Something like that. See the marks on the bones and draw conclusions. Examine the surroundings, whatever evidence of life was around the find in the soil.
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