Ah, Benny's parents, thanks for coming.

Hiya.

So, Benny has really blossomed this term.

You're telling me, he outgrew his bike. We sold it, on eBay.

Oh, that's not quite what I meant.

It's free to sell on there.

Free to sell?

Easy too. Sold Benny's bike, your guitar, my jacket.

You sold my guitar?

Shall we talk about Benny?

When it's this easy to sell for free, you can't help but say when it's eBay.

Things people love. T's and Cs apply, exclusive vehicles.

Welcome to Science Talk, the weekly podcast of Scientific American for the seven days starting January 3rd.

I'm Steve Merski. This week on the podcast, Gordon Smith is going to discuss the lack of any randomized control trials to see if parachutes are really effective. We'll test your knowledge about some recent science in the news. And first up, science journalist Chip Walter on being human. He's an expert.

He is a human.

Walter is the author of an article in the current issue of Scientific American Mind magazine called Why Do We Cry?

That article is adapted from his book, Thumbs, Toads and Tears, and Other Traits that Make Us Human.

To find out more about being human, I called Walter at home in Pittsburgh. Hey, Chip, how are you? Great, great. I'm doing well. How are you? Pretty good. Good to talk to you. The basic theme of the book is pretty obvious, but want you to talk about that a little bit and also tell us why you decided you wanted to write this book. I guess it was really my attempt to try to figure out what makes us tick.

I think it got started whenever I was working on a documentary on the evolution of intelligence

for PBS.

And I thought, well, maybe there are, how could you get your mind around it?

And I began to look at other animals and say,

...