Yup. That story pointed out the perils of time travel. One of the hunters who went back to the Cretaceous (or Jurassic? Anyway...)disobeyed instructions, went off the path and stepped on a butterfly thingie. When the time travellers got home, everything had changed. Of did Ray Bradbury write this story?? I forget! Easy to imagine, however,that a small mole thing with didn't get to eat that butterfly 70 million years ago, and died....and with that small death, the entire history of the world changed. Humbling, actually...