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  • Who are we?

  • That is the big question.

  • And essentially we are just an upright-walking, big-brained,

  • super-intelligent ape.

  • This could be us.

  • We belong to the family called the Hominidae.

  • We are the species called Homo sapiens sapiens,

  • and it's important to remember that,

  • in terms of our place in the world today

  • and our future on planet Earth.

  • We are one species

  • of about five and a 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,

  • or let's say, at least 16 upright-walking apes

  • that have existed over the past six to eight million years.

  • But as far as we know, we're the only upright-walking ape

  • that exists on planet Earth today, except for the bonobos.

  • And it's important to remember that,

  • because the bonobos are so human,

  • and they share 99 percent of their genes with us.

  • And we share our origins with a handful of the living great apes.

  • It's important to remember that we evolved.

  • Now, I know that's a dirty word for some people,

  • but we evolved from common ancestors

  • with the gorillas, the chimpanzee and also the bonobos.

  • We have a common past, and we have a common future.

  • And it is important to remember that all of these great apes

  • have come on as long and as interesting evolutionary journey

  • as we ourselves have today.

  • And it's this journey that is of such interest to humanity,

  • and it's this journey that has been the focus

  • of the past three generations of my family,

  • as we've been in East Africa looking for the fossil remains

  • of our ancestors to try and piece together our evolutionary past.

  • And this is how we look for them.

  • A group of dedicated young men and women walk very slowly

  • out across vast areas of Africa,

  • looking for small fragments of bone, fossil bone, that may be on the surface.

  • And that's an example of what we may do as we walk across

  • the landscape in Northern Kenya, looking for fossils.

  • I doubt many of you in the audience can see

  • the fossil that's in this picture,

  • but if you look very carefully, there is a jaw, a lower jaw,

  • of a 4.1-million-year-old upright-walking ape

  • as it was found at Lake Turkana on the west side.

  • (Laughter)

  • It's extremely time-consuming, labor-intensive

  • and it is something that is going to involve a lot more people,

  • to begin to piece together our past.

  • We still really haven't got a very complete picture of it.

  • When we find a fossil, we mark it.

  • Today, we've got great technology: we have GPS.

  • We mark it with a GPS fix,

  • and we also take a digital photograph of the specimen,

  • so we could essentially put it back on the surface,

  • exactly where we found it.

  • And we can bring all this information into big GIS packages, today.

  • When we then find something very important,

  • like the bones of a human ancestor,

  • we begin to excavate it extremely carefully and slowly,

  • using dental picks and fine paintbrushes.

  • And all the sediment is then put through these screens,

  • and where we go again through it very carefully,

  • looking for small bone fragments, and it's then washed.

  • And these things are so exciting. They are so often the only,

  • or the very first time that anybody has ever seen the remains.

  • And here's a very special moment, when my mother and myself

  • were digging up some remains of human ancestors.

  • And it is one of the most special things

  • to ever do with your mother.

  • (Laughter)

  • Not many people can say that.

  • But now, let me take you back to Africa, two million years ago.

  • I'd just like to point out, if you look at the map of Africa,

  • it does actually look like a hominid skull in its shape.

  • Now we're going to go to the East African and the Rift Valley.

  • It essentially runs up from the Gulf of Aden,

  • or runs down to Lake Malawi.

  • And the Rift Valley is a depression.

  • It's a basin, and rivers flow down from the highlands into the basin,

  • carrying sediment, preserving the bones of animals that lived there.

  • If you want to become a fossil, you actually need to die somewhere

  • where your bones will be rapidly buried.

  • You then hope that the earth moves in such a way

  • as to bring the bones back up to the surface.

  • And then you hope that one of us lot

  • will walk around and find small pieces of you.

  • (Laughter)

  • OK, so it is absolutely surprising that we know as much

  • as we do know today about our ancestors,

  • because it's incredibly difficult,

  • A, for these things to become -- to be -- preserved,

  • and secondly, for them to have been brought back up to the surface.

  • And we really have only spent 50 years looking for these remains,

  • and begin to actually piece together our evolutionary story.

  • So, let's go to Lake Turkana, which is one such lake basin

  • in the very north of our country, Kenya.

  • And if you look north here, there's a big river that flows into the lake

  • that's been carrying sediment and preserving the remains

  • of the animals that lived there.

  • Fossil sites run up and down both lengths of that lake basin,

  • which represents some 20,000 square miles.

  • That's a huge job that we've got on our hands.

  • Two million years ago at Lake Turkana,

  • Homo erectus, one of our human ancestors,

  • actually lived in this region.

  • You can see some of the major fossil sites that we've been working

  • in the north. But, essentially, two million years ago,

  • Homo erectus, up in the far right corner,

  • lived alongside three other species of human ancestor.

  • And here is a skull of a Homo erectus,

  • which I just pulled off the shelf there.

  • (Laughter)

  • But it is not to say that being a single species on planet Earth is the norm.

  • 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.

  • Where did these things come from?

  • That's what we're still trying to find answers to,

  • and it is important to realize that there is diversity

  • in all different species, and our ancestors are no exception.

  • Here's some reconstructions of some of the fossils

  • that have been found from Lake Turkana.

  • But I was very lucky to have been brought up in Kenya,

  • essentially accompanying my parents to Lake Turkana

  • in search of human remains.

  • And we were able to dig up, when we got old enough,

  • fossils such as this, a slender-snouted crocodile.

  • And we dug up giant tortoises, and elephants and things like that.

  • But when I was 12, as I was in this picture,

  • a very exciting expedition was in place on the west side,

  • when they found essentially the skeleton of this Homo erectus.

  • I could relate to this Homo erectus skeleton very well,

  • because I was the same age that he was when he died.

  • And I imagined him to be tall, dark-skinned.

  • His brothers certainly were able to run long distances

  • chasing prey, probably sweating heavily as they did so.

  • He was very able to use stones effectively as tools.

  • And this individual himself, this one that I'm holding up here,

  • actually had a bad back. He'd probably had an injury as a child.

  • He had a scoliosis and therefore must have been looked after

  • quite carefully by other female, and probably much smaller,

  • members of his family group, to have got to where he did in life, age 12.

  • Unfortunately for him, he fell into a swamp

  • and couldn't get out.

  • Essentially, his bones were rapidly buried

  • and beautifully preserved.

  • And he remained there until 1.6 million years later,

  • when this very famous fossil hunter, Kamoya Kimeu,

  • walked along a small hillside

  • and found that small piece of his skull lying on the surface

  • amongst the pebbles, recognized it as being hominid.

  • It's actually this little piece up here on the top.

  • Well, an excavation was begun immediately,

  • and more and more little bits of skull

  • started to be extracted from the sediment.

  • And what was so fun about it was this:

  • the skull pieces got closer and closer to the roots of the tree,

  • and fairly recently the tree had grown up,

  • but it had found that the skull had captured nice water in the hillside,

  • and so it had decided to grow its roots in and around this,

  • holding it in place and preventing it from washing away down the slope.

  • We began to find limb bones; we found finger bones,

  • the bones of the pelvis, vertebrae, ribs, the collar bones,

  • things that had never, ever been seen before in Homo erectus.

  • It was truly exciting.

  • He had a body very similar to our own,

  • and he was on the threshold of becoming human.

  • Well, shortly afterwards, members of his species