Dinosaurs and people coexist only in books, movies and cartoons. The last dinosaurs – other than birds – died out dramatically about 65 million years ago, while the fossils of our earliest human ancestors are only about 6 million years old.
An asteroid impact alone killed the dinosaurs
A layer of iridium-rich rock marks the impact 65 million years ago of a 10-kilometre asteroid in shallow water covering what is now Mexico’s Yucatan peninsula. That impact formed the 180 kilometre-wide Chicxulub crater. There is no convincing evidence that any non-avian dinosaurs survived the aftermath of the impact. Yet we are still not totally sure how the dinosaurs died.
The impact itself could only have killed the dinosaurs in the immediate vicinity of the crater. But it also produced devastating after-effects including giant tsunamis, rain that may have been as acidic as battery acid, and clouds of dust that darkened and cooled the globe for months or even decades.
Another theory suggests that before the impact, dinosaurs were already dwindling as falling sea levels and volcanic eruptions took their toll. A combination of those effects probably wiped out the dinosaurs.
Dinosaurs died out because they were unsuccessful in evolutionary terms
Dinosaurs survived for more than 150 million years, so they cannot be considered unsuccessful. Hominids have lived for only 6 million years, and Homo sapiens date back no more than 200,000 years. Dinosaurs out-competed other animals of their era, but they lost the battle to survive the effects of the asteroid impact.
Dinosaurs died out because mammals ate their eggs
Dinosaurs coexisted with mammals for 150 million years. Although dinosaur nests were undoubtedly vulnerable, the most dangerous predators were probably smaller dinosaurs. Most mammals of the time were probably too small to eat the eggs of large dinosaurs.
