This is scientific American's 60 second science. I'm Christopher Intalyata. Got a minute?

Chimpanzies spend about half their day chewing.

You know, and for context, you know, think about how much time a day you spend chewing.

Daniel Lieberman, a professor of human evolutionary biology at Harvard University.

So how did we make that transition from spending most of our day or half of our day chewing to spending, you know, less than 5%.

Now cooking certainly tenderizes food, making it easier to chew and digest, but evidence for human cook fires goes back only about 500,000

years, if that. And Homo erectus had already evolved weaker jaws and smaller teeth more than a million years before that. So Lieberman and

his colleague Catherine Zink began their investigation by recreating a Paleolithic dinner.

Yams, carrots, beets, and goat meat.

If you were to try to eat some raw goat with your teeth, you would find that you would chew and chew and chew.

It's like bubblegum.

Lucky volunteers got to experience that by chewing the food, either in its wild untenderized

state or after it was bashed or sliced with Flintstonian tools.

And as the study subjects ate, the researchers monitored the frequency and

force of each chew. And they found that a diet of abundant pre-sliced meat with a side of

pounded root vegetables might have saved Homo erectus 2.5 million chews per year,

meaning less need for those big bulky jaws and teeth.

The research is in the journal Nature. Of course these days processed food has a pretty bad rap, but for our ancestors food processing was key.

We live such modern lives that it's hard for people today to imagine what it was like to cook and eat and hunt and live in those times and that for the vast majority of our of our

evolutionary history our ancestors had to work pretty hard to chew their

dinner. Something for you to chew on, perhaps over dinner tonight.

Thanks for the minute. For Scientific Americans 60 Second Science, I'm Christopher and Dahlia.

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