Dear Brileigh,

If you looked inside a T. rex mouth, you’d see some 12-inch teeth. That’s longer than my tail!

I asked my friend Aaron Blackwell if dinosaurs used those big chompers on humans. He’s an anthropologist who studies human biology at Washington State University. He told me dinosaurs and humans didn’t live at the same time.

“Dinosaurs died out 65 million years ago—before there were even primates,” Blackwell said. “So, they could never have eaten a human or even a monkey.”

Scientists think a giant asteroid killed the dinosaurs. It was moving very fast—about 45,000 miles per hour. It made a massive crater when it slammed into the ground.

The blast from the crash set off disasters all over the planet. There were probably tidal waves, earthquakes and wildfires. Plus, the asteroid came at a really bad time. Earth had lots of intense volcano activity then.

The crash also threw soot and debris into the air. That probably made the atmosphere dirty. Less sunlight could get through, so Earth was darker and colder. That was bad news for plants and animals.

About 75% of the animals on Earth died, including most dinosaurs. The only dinosaurs that survived were the ancestors of birds.

That changed life on Earth forever. With the dinosaurs gone, many new kinds of mammals evolved. That’s why the time after the asteroid crash is called the Cenozoic Era, or Age of Mammals.

Some of those new mammals were primates—like monkeys, apes and their cousins. Blackwell told me the first primates appeared about 60 million years ago. They were small animals that looked like tree shrews.

Drawing of early primate
Purgatorius mckeeveri was an early primate that lived shortly after the dinosaurs died out. Illustration by Andrey Atuchin, National Science Foundation Multimedia Gallery.


It would be a long time before primates began walking on two feet. That probably happened between 4 million and 7 million years ago. The first apes to do it had very long arms for swinging in trees. To walk upright, they needed a flexible spine. They also needed strong ankle and knee bones.

Actual humans—called Homo sapiens by scientists—showed up between 200,000 and 300,000 years ago. By that time, the dinosaurs had been gone nearly 65 million years.

There were other dangerous animals to look out for though.

“Apes and early humans were likely eaten by leopards, saber-tooth tigers, hyenas, wolves and maybe a crocodile or a Komodo dragon,” Blackwell said.

In case you’re wondering, cats like me weren’t dinosaur snacks either. The first cat—called Proailurus—lived about 25 million years ago. Humans and cats have been friends for about 10,000 years.

Now that’s a happy ending.


Dr. Universe