Where Did Human Beings Originate?

Transcript

GUY RAZ, HOST:

So this whole story about all the things that came before us and how we got here, it's pretty hard to wrap your head around because the scale is so huge. So how do you explain it?

LOUISE LEAKEY: I like to use a roll of toilet paper.

RAZ: And by the way, this is the renowned paleontologist Louise Leakey.

LEAKEY: So if you lay out a toilet roll which is 400 sheets in length and you actually think about where the dinosaurs, which everybody's familiar with, comes in on the nineteenth sheet from the end, they go extinct on the fifth sheet from the end, they're around for 14 or so sheets of that toilet roll. At that point, it gave rise to the mammals. And our species, Homo sapiens, only came into being in that very last millimeter of that last sheet, the last 200,000 years.

RAZ: A millimeter of the four-hundredth sheet on a roll of toilet paper, that's the whole history of our species. And until very recently, we didn't even know that much and what we do know about our origins is thanks, in large part, to Louise Leakey's family. Their story in Africa all started with her great-grandparents. They were missionaries who settled in Kenya's Kikuyu highlands.

LEAKEY: And that's where Louis, my grandfather, was born and he really grew up speaking Kikuyu and Swahili and collecting snakes and animals, and finding small little obsidian flakes as a child, which I think really instilled within him a sense of excitement. And I think that really sowed the seed, he was convinced he was going to find the answers to our past in Africa rather than outside of Africa, which is what the conventional thinking was at that time.

RAZ: OK so bit of explanation here - up until really the late 1940s, most serious paleontologists believed in something called the Out of Asia Theory and it basically argued that our species developed in Asia and the fossil record at the time seemed to confirm it. But Louis Leakey was an outlier, he was absolutely convinced that humans came from Africa and he became obsessed with proving it, even though most self-respecting fossil hunters were digging in Asia.

LEAKEY: They had finds from Indonesia, from China and to have imagined that you could've found fossils in Africa didn't seem right. What they didn't know was the fossils that were found outside of Africa were all much younger than the fossils that they would then go on to find in Africa so of course, the conventional thinking was that Louis was looking in quite the wrong place.

RAZ: But Louis Leakey and his wife Mary persisted, they spent decades digging for clues in Tanzania in a remote area known as Olduvai Gorge.(SOUNDBITE OF DOCUMENTARY BY NATIONAL GEOGRAPHIC)

LOUIS LEAKEY: Olduvai Gorge gives us one of the most remarkable stories of the past, the last chapter of the Earth's history, starting from the present day right away back to two million years.

RAZ: This is Louis Leakey from an old National Geographic documentary and it was at Olduvai Gorge where the Leakey's would upend the entire field of paleoanthropology in 1959.

LEAKEY: When my grandmother Mary found the skull of Zinjanthropus.

RAZ: Now, the skull of Zinjanthropus was one of the most significant hominid fossils found up to that point. It was 1.75 million years old, far older than other fossils found in China and Indonesia and it proved that our ancestors came from and evolved in Africa.

LEAKEY: So that find really put then Africa on the map and made people then turn to Africa.

RAZ: It changed our entire understanding of where we came from and that find launched a family dynasty of paleontologists - their sons Richard and Jonathan, and eventually their granddaughter Louise, who explained her ideas on the TED stage.

(SOUNDBITE OF TED TALK)

LEAKEY: Who are we? That is the big question. And essentially, we are just an upright, walking, big brain, super intelligent ape. We belong to the family called the Hominidae. We are the species called Homo sapiens sapiens. We are one species of about 5 and half-thousand mammalian species that exist on planet Earth today and that's just a tiny fraction of all species that have ever lived on the planet in past times. We're one species out of approximately - let's say at least 16 - upright walking apes that have existed over the past 6 to 8 million years, but as far as we know we're the only upright walking ape that exists on planet Earth today. And it's important to remember that and in terms of our place in the world today and our future on planet Earth. In fact, if you go back in time it is the norm that there are multiple species of Hominids or of human ancestors that coexist at any one time. We've only been around for the past 200,000 years as a species, yet we've reached a population of more than 6-and-a-half billion people. But what's happened is, our technology has removed the checks and balances on our population growth. My father so appropriately put it that we are certainly the only animal that makes conscious choices that are bad for our survival as a species. Can we hold it together? It's important to remember that we all evolved in Africa, we all have an African origin. We have a common past and we share a common future. Evolutionarily speaking, we are just a blip. We're sitting on the edge of a precipice. We have the tools and the technology at our hands to communicate what needs to be done to hold it together, today. Will we do that, or will we just let nature take its course?

RAZ: In a sense, what you do by looking into the past is almost like a window into the future.

LEAKEY: Well, that's absolutely right. I think when you work on fossils and you realize that a species is there and it's abundant for quite a long period of time and then at some point it's no longer there - and so when you look at that bigger picture, yes, you realize that either you change and adapt, or as a species, you go extinct.

RAZ: I mean, you think about Neanderthals who lasted for half-a-million years, right and we've been around for 200,000. I mean, let's just talk about 5,000 years from now. I mean, do you think it's likely that we will be here in 5,000 years?

LEAKEY: I couldn't answer that question. I really, I stop and think about it quite often. As a species yes, we probably could be here, but in what numbers and possibly far fewer, if we're really going to sustain ourselves on the planet. But every species becomes extinct, at some point we will go extinct. The question is, as Homo sapiens, are we going to be able to adapt to the change that we're actually part of? We're causing such dramatic changes to the planet so yes, you do stop and think, I wonder where we're headed.

RAZ: Louise Leakey is a third-generation paleontologist from the legendary Leakey family. You can check out her full talk at ted.npr.org.

Our show today, How It All Began - ideas about our collective past. I'm Guy Raz and you're listening to the TED Radio Hour from NPR. Transcript provided by NPR, Copyright NPR.