system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - What stopped dinosaurs re-emerging as the dominant species after the meteor event?

I know that the meteor event made them extinct, but why did humans emerge ahead of dinosaurs? Was it something about the state of earth and the relative advantages species like humans had?
gpt
Well they were dead, for starters - even if the world had returned to the Cretaceous climate quickly the dinosaur lineages had been annihilated, save for some small birds.  They would have had to re-evolve from scratch, a process that’s both slow and random.

Reptile and mammal lineages fared much better during the extinction event, and were positioned to flood the newly opened environment with mammal descendants that played the same general environmental function.  Once large grazing mammals showed up there’s no space for large grazing reptiles or birds to compete with them.