If dinosaurs hadn’t died out, humans might not be here

In “The Last Days of the Dinosaurs,” Riley Black explains why they ”needed to step off the evolutionary stage” so the age of mammals could appear.

Riley Black is the author of "The Last Days of the Dinosaurs: An Asteroid, Extinction, and the Beginning of Our World."

What killed the dinosaurs? As science writer and amateur paleontologist Riley Black explains in “The Last Days of the Dinosaurs: An Asteroid, Extinction, and the Beginning of Our World,” the answer is just one part of a grand story of devastation and rebirth. Ms. Black recently spoke with Monitor.

Your book focuses on the Hell Creek Formation area, a rocky region in and near Montana. Why is that?

Most of what we know about the 75% of species on Earth that went extinct at the end of the Cretaceous Era – including the non-avian dinosaurs – comes from the Hell Creek Formation. It’s a group of rock layers that date back to between about 65 million to 68 million years ago, providing an almost continuous record of how the extinction played out. 

What surprised you about dinosaur extinction?

I was really shocked to discover about how fast it happened. Often, the imagery that surrounds this mass extinction involves emaciated dinosaurs in a winter landscape just kind of tottering around as they’re shuffling off into extinction. 

We now understand that many species that went extinct did so basically in the first 24 hours. When the asteroid struck, there was a lot of debris and rock that shot up into our atmosphere. Little pieces started to fall back down to Earth all over the planet. They created friction, like when a shuttle re-enters the atmosphere. 

Any single piece of debris would be insignificant, but the total mass of the rock heated the atmosphere to such a degree that it basically set the air to broil. Geologists estimate that air temperatures reached 500 degrees Fahrenheit, and some forests spontaneously burst into flames. 

What were keys to survival for the species that remained?

It seems that living in water or being able to find shelter underground was really critical. Many are able to survive by staying underwater because even extreme heat dissipates relatively quickly through water. A frog or a turtle at the bottom of a Cretaceous lake or pond isn’t going to be all that affected.

What did the asteroid collision mean for mammals and, later, for humans?

If this impact never happened, the dinosaurs like T. rex and triceratops that we love so much would probably still be here. They’d been around for more than 115 million years to that point, and there’s no reason to think they would have disappeared, barring another similar event. 

On the other hand, if the extinction played out just a little bit differently, our ancestors might have gone extinct.

We love our dinosaurs, and we want to see them alive. But if they were here, we probably wouldn’t be here to enjoy it. We really needed dinosaurs to step off the evolutionary stage in order for the age of mammals to appear.

Is there a take-home message in this story?

It’s a reminder of how vibrant and resilient life can be. Something that might seem distant like the fate of a triceratops relates back to our own story of where we came from. Since the first life appeared on Earth, about three and a half billion years ago, there’s always been something alive on this planet. Life has always found a way to come back [after disaster] and undergo a revival and resurgence. 

But you never know when these catastrophic events are going to occur. That’s why diversity in nature – lots of different species expressing themselves in all these different ways – is so important.

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