Why did humans lose their body hair? Why did they start walking on their hind legs? Why did they develop big brains? I think that the answer to all three questions is sexual selection.
You have to remember that not every creature that was evolving left behind its skull or its tools for our convenience tens of thousands of years later. Most bones or most tools rot or get buried and are never found again.
Our evolution could have gone in different directions a lot of times. We could have gone extinct at some points. We might not have gotten our big brains, or Neanderthals might have made it while we did not.
Humans are upsetting a fragile balance that their own human ancestors established.
Back in humanity's hunter-gatherer days, you only ate meat if you'd recently made a kill, which required a huge amount of effort, and was therefore relatively rare. There's a reason humans only have one set of incisors to rip our meat apart: we're not supposed to eat the stuff at every meal.
I'm the product of 6 million years of evolution? Come on, man. I crawled out of a swamp yesterday.
As you know, the fossil record includes not only the ancestors of crocodiles and whales, but also the ancestors of human beings. And this, of course, is why evolution remains controversial.
But what really excited me was the idea that humans had a tremendous pre-history that went back millions of years. I wanted to go to Africa to find some of these creatures.
Good food for free has been the holy grail of foragers since our ancestors first climbed down from the trees.
Three and a half million years ago our ancestors - yours and mine - left these traces [indicates footprints]. We stood up and parted ways from them. Once we were standing on two feet, our eyes were no longer fixated on the ground. Now, we were free to look up and wonder.
To investigate the history of man's development, the most important finds are, of course, hominid fossils.
Most of our ancestors were not perfect ladies and gentlemen. The majority of them weren't even mammals.
Our ape-like and arboreal ancestors entered upon the first of many short cuts. To crack a marrow-bone with a rock was the act which fathered the tool, and between the cracking of a marrow-bone and the riding down town in an automobile lies only a difference of degree.
Are we the first hominids? I really, really, really doubt it.
I've always been excited to know how we got here.
Haunted since the day its discovery was projected all over the world in 1994, I, like many others, have always wanted to see inside the Chauvet cave, site of the world's earliest known cave art. Quite rightly, we will never go. It is closed to the public.
How about Pithecanthropus Erectus? Was it really he who ate the apple? Or was it Homo Pekiniensis?
We feel closer to the drawings on the walls of Chauvet than the painting of, say, an Egyptian mural. These artists are not remote ancestors; they are brothers. They saw like us; they drew like us. We wear essentially the same clothes against the cold.
If you were to go to the National Museum in Addis Ababa, you would walk into a huge room filled with literally tens of tons of fossils, and most of them would be elephants and rhinos and hippopotamus and monkeys and giraffes and antelopes and so on. Hominids are very rare in the landscape, and it's very rare to find them.
Selam is our most complete skeleton of a three-year-old girl who lived and died 3.3 million years ago. She belongs to the species known as Australopithecus afarensis.
Until about 30,000 years ago, there were at least five other species of humans on the planet. Homo Sapiens, our ancestors, lived mainly in East Africa, and you had the Neanderthal in Europe, Homo Erectus in part of Asia, and so forth.
Just as your own existence is unlikely and far from inevitable, the evolution of modern humans as a species depended on a whole string of chance events - some happening in the environments our ancestors inhabited, and some inside their own bodies, including random mutations in their DNA.
It is now generally accepted that the roots of our ethics lie in patterns of behavior that evolved among our pre-human ancestors, the social mammals and that we retain within our biological nature elements of these evolved responses. We have learned considerably more about this responses, and we are beginning to to understand how they interact with our capacity to reason.
