The Traits That Make Us Humans

In his new book Thumbs, Toes and Tears, author Chip Walter explores the physical and behavioral traits that are unique to humans. He notes that humans are the only creatures to cry, and that technological advances mark another front in our evolution.

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The elephant has its trunk, writes author Chip Walter. Bombardier beetles manufacture and precisely shoot boiling hot toxic chemicals from their tails. Peregrine falcons have wings that propel them unerringly through the air at 70 miles an hour to their catch. These traits define these creatures and determine the way they act. But, Walter asks, what you unique traits shape and define us?

Walter is the author of the new book, "Thumbs, Toes and Tears: And Other Traits That Make Us Human."

Thanks for joining us.

Mr. CHIP WALTER (Author): Thank you, great to be here.

SEABROOK: So I gather that thumbs, toes and tears are three of these traits that make us human. Define human for us from an evolutionary point of view.

Mr. WALTER: Anything that helps to define and explain the particular creature that we are as human, and we are remarkable and so different from the other creatures. What made me think about it was, you look around at other animals and you see defining traits about them. So you look at an elephant and you say, there's that trunk, that's what really is different about them. So I'll bet if I look closely at that I can figure a lot of things out about that animal.

So I thought, well, what are the things that are unique to us? You know, the physical and behavioral traits. I mean, there's obviously lots of things that we do that are different from other animals. But I thought, if you kept pushing it back and asking what are the baseline traits that we have, then you would arrive at these six. And the six are, you know, our big toe, which seems as about as homely as you can get.

(Soundbite of laughter)

Mr. WALTER: And then you have thumbs, opposable thumbs, which a lot of people think about.

SEABROOK: Okay. So, toes, thumbs - what else?

Mr. WALTER: Right. We cry. We cry tears of emotion. We're the only creature that does that. And we kiss and we laugh. And then, of course, the thing that we're doing right now, which is we make these odd, intricate noises at one another that somehow we understand. And that's because we have very unique throats; these kind of long, elegant throats with a hundred muscles in them can make more sounds than any other creature.

SEABROOK: So I think I've seen chimps use tools, kiss. You know, they use these things, albeit rudimentary, aren't they doing these things?

Mr. WALTER: Well, there's a continuum in evolution. It's never like, you know, it stops here and starts there. So these are called homologs by scientists, you know, where you see the kinds of behavior that may have led to the behavior that we have. But chimps do not have - and they are our closet relatives - they do not have the fine motor control that we have in our fingers and our thumbs. And if you sit and you rotate your thumbs widely, chimps cannot do that. And they can't touch the very tips of their small fingers.

They have opposable thumbs, but they don't have thumbs that are opposable in our particular way. And the way that we have it enables us to grip and hold things like a baseball or like a bat. This gave us the ability to make tools, which, strangely enough, actually led to creating a brain that was primed for language.

SEABROOK: Explain to me how making tools led to a bigger brain.

Mr. WALTER: Well, think about when you make a tool. You have to do things in sequence, you know. So if you've been to IKEA, you know that if you don't get A to B and B to C, you've got trouble.

(Soundbite of laughter)

SEABROOK: Big trouble.

Mr. WALTER: Right. Right. We've all been there, right?

SEABROOK: Right.

Mr. WALTER: And so you have to be able to say, well, before I have to pick up something and then I have to bring it down and hit something, and so the first thing it does is it kind of causes you to think linearly. And then in the course of even thinking that way, you have to be able to say, well, all right, I'm going to do this thing first and then I'm going to do this next thing. And then that makes - you have to be the subject of the sentence, the thing that you're hitting is the object of the sentence, and it makes you see the world in the way that we later had to manipulate ideas in order to make language.

SEABROOK: So you're saying that the act of doing things in order makes talking about them possible?

Mr. WALTER: Yeah, it begins to shape the brain so that it sees the world in a way that it can control and manipulate objects. And then later, that capability enabled us to control and manipulate thoughts and ideas.

SEABROOK: So many things have been said about animals before that have been disproved, like that they have no higher thought, no use of tools, no emotion. They were thought to have no emotion for many decades.

Mr. WALTER: Right.

SEABROOK: And now it's generally thought that all of those have been debunked. Even octopi have...

Mr. WALTER: Right.

SEABROOK: ...higher thought. You know, many animals use tools.

Mr. WALTER: Right. Right. I guess one of the differentiations with regard to tools is there seems to be quite a few animals that will use tools or they'll use other objects around, you know, to accomplish the things that they want. What we haven't found is that there isn't any creature that makes tools and takes the objects around them and reshapes them. So there's obviously a qualitative difference between what we do and other creatures do.

SEABROOK: You end your book with an epilogue about cyber sapiens.

Mr. WALTER: Yeah.

SEABROOK: Do you see that technological evolution actually changing what humans are fundamentally?

Mr. WALTER: I think what it is going to represent is another stage in evolution. Whenever the first tool was made, that changed the evolutionary picture completely, forever. Once you had a creature that could start to make tools and manipulate the world, then that changes the evolutionary picture.

SEABROOK: And we're starting to be able to manipulate the DNA, too.

Mr. WALTER: Right, right. I mean, we're actually playing with the genetics, so we're changing ourselves. And so I think the next step is that you start to see a blurring of the lines between biology and technology, between reality and virtual reality, between humans and machines. And that's, you know, a result of a kind of cultural evolution that is linked to our technological evolution.

So now what's happening is that you're getting to the point where we're really being able to play with ourselves, what makes us tick, and the technologies around the world are beginning to meld and blur so that soon, for example, with nanotechnology you'll have machines that are working at the molecular level, which means that they're working at the sub-cellular level.

So I think that what we'll see is that the real evolution isn't going to be physical, and it's not going to be DNA-driven, it's going to be technological. We may evolve essentially into a different creature that forsakes its DNA, and we use the machines that we create, albeit extremely tiny machines, to pretty much create a new kind of creature.

SEABROOK: Chip Walter is the author of "Thumbs, Toes and Tears, and Other Traits that Make Us Human." Thank you so much for joining us.

Mr. WALTER: Thank you. It's been a pleasure.

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Thumbs, Toes, And Tears

And Other Traits That Make Us Human

by Chip Walter

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