GEOFF BENNETT: Yuval Noah Harari as a professor of history who is renowned for his broad and thought-provoking perspectives on human history.

Harari, who is the bestselling author of "Sapiens," recently released a new volume of this work called "Unstoppable Us" for younger readers.

Tonight, he shares his Brief But Spectacular take on what it means to be human.

YUVAL NOAH HARARI, Author, "Unstoppable Us": I think it's more difficult to write for kids than for adults.

When you write about complicated stuff,and you are actually not sure what you want to say, then, with adults, you can just cover yourself by talking with these very long, complicated sentences.

With kids, it doesn't work.

You need to speak very clearly.

And, for that, you really need to think deeply, to know, what do you actually want to say?

When I was a kid, I asked these big questions about life, I mean, what are we doing here, what is this all about?

And I think what struck me the most is not that the adults often had no answers, is that they were not concerned about the fact that they really don't understand the world.

In a way, I wrote "Unstoppable Us" to answer at least some of the questions that really bothered me when I was 10 or 12.

How did we get here?

If you look at any major human achievement, it is always based on large-scale cooperation.

You want to build pyramids, you want to fly to the moon, you want to create an atom bomb, you want to build a health care system, you always need thousands of people cooperating together.

And we are the only mammals that can do that.

How do we do that?

By inventing and believing fictional stories.

You can't do that with chimps.

Humans, unfortunately, are -- we are very smart, but, despite our wisdom, we keep doing some very stupid things.

We know that nuclear weapons could destroy the whole of human civilization.

We know that now artificial intelligence can escape our control, and yet we keep on producing it.

The three, I think, biggest challenges that face humankind today in the 21st century are ecological collapse, disruptive technologies like artificial intelligence and the threat of nuclear war.

The one thing everybody needs to know about A.I.

is that it's the first technology in history that can make decisions by itself and can create new ideas by itself.

It's often compared to previous technological breakthroughs like the printing press or the atom bomb.

It's completely different.

Printing presses could not decide what book to print.

Atom bombs could not decide by themselves which cities to destroy.

But A.I.

can do that.

The dedication of the book says that our ancestors made the world what it is, and we can now decide what it will become.

The main message of the book and also in the title, "Unstoppable Us," is that humans, all humans are the most powerful entity on the planet, and we should own it.

We should acknowledge our immense power, because only then we can also take responsibility for what we are doing with this power.

My name is Yuval Noah Harari, and this is my Brief But Spectacular take on what it means to be human.

GEOFF BENNETT: And you can find additional Brief But Spectacular episodes online at PBS.org/NewsHour/Brief.