It's very hard to kill every single human with an asteroid. It should be a really huge, planet-busting asteroid. A planetoid, really. Those are rare. And even

It's very hard to kill every single human with an asteroid. It should be a really huge, planet-busting asteroid. A planetoid, really. Those are rare. And even if you have 1000 humans surviving, it didn't happen. What helps humans over dinosaurs: humans can live in extreme conditions (dinosaurs are very picky), and humans can conserve food outside of their bodies and live on it for a long time. Humans are small and adaptable, dinosaurs are large and very fragile, as all big animals are.