system
A chat on subreddit /r/NoStupidQuestions
human
To answer that we'd need to know why *humans* developed intelligence, and unfortunately we're still in the dark about that question. 

We have some theories about human intelligence though, and since none of them generally apply to dinosaurs, they're all good candidates for explaining why dinosaurs didn't. So ... pick your favorite from the following:

1) Versatile migration -- our legs let us travel in almost any climate or biome and set up home there. New environments mean new challenges, and you'll need smarts to survive when you get there. Which may surprisingly lead to ...

2) Long childhoods -- walking upright is cool, but it creates a *lot* of problems when it comes to giving birth. Extremely wide hips make walking awkward, so hips have to be narrower. But if the hips are narrow the baby needs to be a lot smaller, which means human babies are essentially all born premature compared to other animals. Hell, it takes us almost a year to learn how to walk across a room. 

But spending a lot of time at home means a lot of mothers are spending a lot of time with other mothers, and ... what's the phrase? Ah, "women, they be talkin!" 

There's a direct line between walking upright, smaller hips, small baby size, long-term settlements, and the development of language.

3) Aaaaand, we get to our conclusion with language. In a a hunter-gatherer society with established settlements and cooperative food gathering, it's important to develop very clear means of communication. 

Other animals can communicate basics like "I'm happy" or "Go the fuck away!" well enough, but it takes a big brain to communicate things like "Okay Thog, we're hunting red deer today. You go around back and get their attention, while Ungo sneaks in from the side and gets them with his spear," or "Oh my gawd Ooona, there are the best red berries on the other side of that hill. You *have* to go taste them!"
gpt
&gt;Oh my gawd Ooona, there are the best red berries on the other side of that hill. You have to go taste them!

Also Ooona: careful with the red berry that tastes good but kills you. Easy to tell apart, it has a more crimson colour and the one that doesn't kill you is more vermilion.