A massive asteroid struck Earth 66 million years ago and profoundly changed our planet. More than three-quarters of plant and animal species went extinct. When the world finally recovered, the only dinosaurs left were birds. Mammals took over most of the roles dinosaurs once filled.
Without that catastrophe, humans wouldn’t be here today. But it also took many other changes to produce the world we now live in. Major shifts in climate, land, and oceans unfolded over tens of millions of years. A warm greenhouse environment, with high levels of gases like carbon dioxide in the atmosphere, became a cooler, drier, icehouse world.
Click to expand images below.
Gastornis model
This giant flightless bird from 50 million years ago was a dinosaur whose flying ancestors survived the asteroid impact.
Sabelites frond
Palm trees can’t grow in Wyoming today; it’s too cold and dry. 45 million years ago, this extinct species thrived in the planet’s greenhouse climate.
Extinct alligator
Crocodiles once lived in the American West, until the climate became too cold. Alligators, like this 25-million-year-old specimen from South Dakota, could handle cooler conditions.
Megacerops skeleton
34 million years ago, as the climate cooled and dense forests became open woodland, massive herbivores like Megacerops evolved in response to the new terrain.
Menoceras bone bed
These pig-sized rhinos from Nebraska probably died at a waterhole during a drought 20 million years ago. Drier weather made such events more common worldwide.
All photos: credit Andy Melien / Yale Peabody Museum