ALAN ALDA (NARRATION) But today, science is gaining unprecedented insights into that way of life thanks to the remains of the Neanderthals themselves, like this fossilized skeleton of a child found in a pit at Roc de Marsal.

The most ambitious approach to Neanderthal forensics is taking place in Leipzig, Germany, at the Max Planck Institute for Evolutionary Anthropology. Here scientists from a range of disciplines are looking for the Human Spark by comparing us with both our living relatives like chimpanzees and other apes, and with our extinct relatives like the Neanderthals, to try to pin down the crucial differences.

ALAN ALDA Why do you care so much about the difference between us and the Neanderthals? Is it a sentimental difference, or it going to really teach us something about who we are, how we’re made, what makes us human?

SVANTE PÄÄBO I think it can potentially teach us a lot. After all, fully modern humans are really unique, in this way in that we spread over the world, colonize all parts of the planet. We can really dominate the ecosystem that the other earlier forms of humans didn’t do, they spread pretty much like other big mammals, like wolves or something like that. It’s something here in our behavior that’s very unique, and to get behind that, what is that thing that makes that possible, I think that’s one of the more fundamental questions that I can think of, that I would really like to find out.

ALAN ALDA (NARRATION) Svante Pääbo heads a project that aims to decipher the entire genetic code of the Neanderthals so that it can be directly compared with our own. Dressed from head to foot in protective clothing, I got to watch how researcher Adrian Briggs drills into Neanderthal bones in search of the tiny fragments of DNA that have survived there.

ALAN ALDA You seem to be taking enormous precautions against contamination. Why is that?

ADRIAN BRIGGS Well, there’s very, very small amounts of DNA left in these bones after so many years in the ground. The amount of DNA that we would normally give off by shedding skin cells for example is the same or more than the amount of actual DNA from the Neanderthal. So in order to really reduce that background DNA then we really have to be as careful as possible. And even then you have to really carefully analyze your results to be sure that you haven’t just sequenced yourself.

ALAN ALDA (NARRATION) The Max Planck team recently completed the first rough draft of the Neanderthal genome. The headline news is that there’s little evidence our ancestors and Neanderthals mated when they met – or at least that they produced any offspring. But so far there is no single genetic smoking gun to explain why the Spark failed to ignite in Neanderthals – in large part because the genetic differences between us and them are turning out to be very, very small.

ALAN ALDA But that small difference between us could be crucial, could mean a great deal about language and thought processes and that kind of thing?

SVANTE PÄÄBO Yes. So the dream is of course to find those few changes that hide in there, that are crucial.

ALAN ALDA (NARRATION) Fulfilling that dream will take more time. But meanwhile the bones are revealing another crucial difference between them and us – what Neanderthals ate. In another lab here at the Max Planck Institute, protein extracted from Neanderthal bones is wrapped in little lead packets ready to be analyzed.

The analysis, of the isotopes of carbon and nitrogen, reveals whether the bone protein came from meat, fish or plants.

MICHAEL RICHARDS We’ve looked at Neanderthals, maybe ten of them now from over about 100,000 years. And what’s been surprising is in every case, the isotope value seem to show that all of their protein was from animal protein. We don’t find evidence that there was any significant amount of plant foods in their diet. It seems strange that over this long period of time, they seem to be doing the same thing. They were getting almost all of their protein from animal protein.

ALAN ALDA (NARRATION) And when Mike Richards says animal protein, he means meat protein.

MICHAEL RICHARDS The Neanderthals, interestingly, don’t seem to have had any fish. Even when they live sort of close to the coast, but mostly when they live inland along these big rivers in Europe that have lots of sturgeon, for example, they don’t seem to be hunting them at all.

ALAN ALDA Does anybody have an idea why that would be so? There it was available.

MICHAEL RICHARDS I think that actually Neanderthals were very successful. They survived much longer than us in Europe. And actually, their adaptation didn’t seem to change very much over the sort of 200,000 years they were in Europe. So it was a very successful adaptation, so why would you change it, and why do something new? Actually, I think conceptually, going from hunting large animals and subsisting off that, to getting something out of the river, small little fish, and small birds, and small game, is something the Neanderthals don’t seem to have ever really done.

ALAN ALDA (NARRATION) In the foothills of the Alps, in the French city of Grenoble, is located the most dramatic of the new scientific studies aimed squarely at answering this central mystery – why the Neanderthals seemed incapable of changing the way of life they inherited from their African ancestors.

This is the world’s biggest X-ray machine, the European Synchrotron Radiation Facility.

Brought here from Belgium to have its teeth X-rayed is the upper jaw of a Neanderthal child.

A laser is used to line up the X-ray beam, which is millions of times more powerful than that from the machine in your dentist’s office.

Also here today to have its teeth X-rayed is the skull of a young Neanderthal found originally in France.

The teeth of both specimens are 50,000 years old, yet their condition would make a modern dentist proud.

TANYA SMITH When we’re growing and developing our teeth, we’re pumping so much mineral into them that they’re almost one hundred per cent mineralized already. So they are almost fossils in our mouths as we’re living today.

ALAN ALDA (NARRATION) And they are fossils with a built-in calendar. Teeth lay down a new layer of enamel every day they are growing, so Tanya Smith can literally count the days of the Neanderthal children’s lives.

TANYA SMITH Effectively, the total period of time you’re growing your teeth gives you a good proxy for how long your childhood is.

ALAN ALDA (NARRATION) This Neanderthal child was thought to be about 6 or 7 years old. But the growth lines in its teeth suggest that it was in fact younger when it died – meaning that it developed faster after birth than children today.

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