What if the dinosaur-killing asteroid never slammed into Earth and the paleo-beasts weren't vanquished from our planet 66 million years ago?
That's the hypothetical that forms the basis of Pixar's "The Good Dinosaur," set to hit the big screens on Nov. 25. The movie maker's answer — that a young Apatosaurus would meet and befriend a cave boy — is cute, but totally off the mark, several paleontologists told Live Science.
"It's completely impossible," said Thomas Williamson, curator of paleontology at the New Mexico Museum of Natural History and Science, referring to dinosaurs ever being alive alongside humans — something that could never happen if the dinosaurs were to survive. [Wipe Out: History's Most Mysterious Extinctions]
Though there were mammals during the dinosaur's reign of the Mesozoic era, these animals were small, no larger than the size of a house cat. It's wasn't until the nonavian dinosaurs went extinct that mammals grew in size and specialty, eventually giving rise to the human lineage about 60 million years later.
"Dinosaurs had been around for over 150 million years when the asteroid hit, and were doing quite well up until that fateful day," said Steve Brusatte, a paleontologist at the University of Edinburgh. If the asteroid hadn't hit Earth, "I have no doubt that they would have kept evolving and thriving.If dinosaurs hadn't perished, "mammals would have never gotten their chance to evolve in that brave new world, free of their dinosaur overlords," Brusatte told Live Science. "Without mammals getting their chance, then there would have been no primates, and then no humans.