Ask Dr. Universe: Dinosaurs dying out opened up space for humans to evolve

Washington State University

Dr. Universe: Did man live with dinosaurs together? – Daniel, 9, Republic of Korea

Dear Daniel,

When I think about dinosaurs, I usually picture the big ones. I think of triceratops with its pointy horns or apatosaurus with its long, long neck.

I asked my friend John Blong if those dinos ever lived with people. He’s an environmental archeologist at Washington State University. He studies early humans.

He told me that people and dinosaurs never lived at the same time. Well, mostly.

Dinosaurs went extinct 66 million years ago when a giant asteroid crashed to Earth. It threw up tons of dust and soot. It made Earth super cold and dark. It stayed that way for a long time. The world became a very hard place to live. Eventually, 75% of all living things died, including all the big dinosaurs.

People didn’t live on Earth at that time. The only mammals that lived back then were tiny. They looked like shrews or moles. It would take millions of years before mammals adapted enough to become primates. Scientists think the first humans showed up about 300,000 years ago. That was long after the dinosaurs died out.

But some dinosaurs survived the asteroid.

“Some of the avian dinosaurs survived,” Blong said. “Over millions of years, they evolved into the birds that we share the planet with today. Many scientists have argued that birds should be considered living dinosaurs.”

The early bird-like dinosaurs were theropods – like T. Rex and velociraptor. These dinosaurs stood on two legs. They were mostly covered in feathers. They might have even been warm-blooded. That means they kept the temperature inside their bodies steady, no matter how cold or hot it was outside. That’s like birds and mammals today.

But those big bird-like dinosaurs didn’t survive. Only animals that weighed less than 50 grams did. That’s about how much a slice of bread weighs. It was easier for small animals to adjust to the changes on Earth and find food.

Over millions of years, the lucky survivors changed little by little until they looked like modern birds.

So, humans have lived with birds – living dinosaurs – for the whole 300,000 years they’ve been on the planet.

Blong told me that big dinosaurs dying out is a reason humans and other mammals are so cool today.

Living things have different jobs in the ecosystems where they live. Those jobs are called niches. When the non-avian dinosaurs died, that left lots of open niches for other animals to fill.

“Primates evolved from that space that was left,” Blong said. “If the dinosaurs were still around – and so occupied those niches – mammals might still just be a bunch of little mice rolling around the planet.”

With them gone, mammals could really dino-soar.

Sincerely,

Dr. Universe

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