When Amanda Henry went through airport security in Washington on her way to Boston she made the inspector nervous when her bag revealed dental instruments – apparently the security officer hates going to the dentist. The officer may have been even more freaked out if she knew the teeth Amanda was on her way to clean with her dental picks belonged to a 100,000-year-old.

A very famous 100,000-year-old at that – at least in archeological circles. The teeth are still all neatly in place in a skull now at the Peabody Museum of Harvard University [tons of images here], where it has resided in secure climate-controlled storage since it was unearthed in the 1930s from a cave in Mount Carmel, in present-day Israel. We had met the skull the day before, when Dan Lieberman had arranged for it to be brought out of storage and introduced to Alan.

Known as Skhul 5, the skull is the oldest known human with almost modern features, and so plays a pivotal role in our story. He poses the central puzzle we’re trying to get to the bottom of: people looked like us apparently long before they started behaving like us – at least according to the commonly accepted view that the modern human mind – with what we are calling the Human Spark – didn’t evolve until tens of thousands of years after the owner of the Skhul skull and his like lived in the Middle East – most likely alongside, or at least at the same time as, their cousins the Neanderthals.

The Human Spark camera rolls while Amanda demonstrates her dental scraping techniques to Alan. Photo: Maggie Villiger

As we’d just been learning from Alison Brooks, it’s now looking increasingly likely that the Human Spark in fact started to glimmer much earlier in Africa, perhaps even before the ancestors of Skhul 5 made their way north. So archeologists would love to know as much as possible about how Skhul 5 lived. It was Alison who told us about Amanda, a student of hers at George Washington University, who – armed with her dental picks – was going to demonstrate to Alan how she’s figuring out what Skhul 5 ate.

After carefully removing the skull from its padded box, Amanda showed us how she very, very gently scrapes dental plaque from the skull’s molars (much more gently than your oral hygienist cleans yours).  Plaque, she explained, is the perfect material to preserve microfossils from the plants Skhul 5 ate – starch grains and tiny silica bodies called phytoliths that Amanda will be able to identify under the microscope and tell what plants they came from.

Amanda’s care in her scraping wasn’t only because, as she reminded us, the skull is priceless, but also because, “I have to leave some plaque behind in case somebody comes up with a different way for studying it in the future.”

Alan wanted to know if she poked around in his teeth, could she find out what he’s eaten.

Amanda: Well it depends, how good are you at brushing and flossing?

Alan: Oh just great, yes.

Amanda: I’ve actually done some experiments where you eat whatever you normally eat for breakfast, lunch and dinner. At the end of the day , you take one of these dental picks…

Alan: And you could say what the person had eaten?

Amanda: Some of it, sure.

Alan: No kidding.

Amanda: It’s quite easy. It’s not just in the plaque. It’s in any of the pellical, basically the scum that builds up on your teeth. As that hardens into plaque then it’s more permanently kept on your teeth. I don’t know, actually, how far back I’d be able to tell what you ate, whether I could just tell this morning what you had for breakfast, or what you had three weeks ago.

Fortunately for Amanda, and despite the astonishingly good shape of Skhul 5’s teeth, he lived a good long time before the invention of dental floss, so she has high hopes of discovering what he ate 100,000 years ago.

Alan summed up the reaction of all of us: “Astonishing.”

- Graham Chedd

Tanya Smith shows 3-D images of Neanderthal teeth photo © Larry Engel, 2008

Graham Chedd here. Last time, I was telling you about our visit to the European Synchrotron Radiation Facility – and about the trouble I got into there.

We’d come to the European Synchrotron Radiation Facility at the invitation of Tanya Smith, who works at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany (where there’s a lot of very cool Human Spark-type research going on, so we’ll be filming there later). Tanya is an expert on teeth, which as she points out are by far the most durable parts of our bodies – in fact they are practically fossilized as they grow. What’s more – and I found this astonishing when she first told me – teeth have daily growth lines hidden inside them, much like tree rings, which can reveal their owner’s early life history – and how quickly they grew up.

Here’s Tanya, alongside some 3-D images of Neanderthal teeth.

Peering inside teeth to see those growth rings needs very powerful X-ray beams – beams millions of times stronger than you get from your dentist. That’s where the synchrotron comes in. And because the X-rays are so potent they are also deadly, which is why there are all sorts of safety precautions. For instance, we were allowed inside the synchrotron while the beam was turned off for routine maintenance for an hour or so, and we were all given special little keys. The synchrotron can’t be turned on until all these keys are returned and in their little locks.

The Emergency Stop button photo © Larry Engel, 2008

There are also big buttons like this everywhere…

including in the room where the teeth were actually scanned. Now, before the beam is activated the room it has to be cleared of people, and to make sure the room is thoroughly checked, there are buttons in the corners that have to be pushed. I volunteered to push one of these buttons – and pushed this one.

Of course, it was the wrong one (pretty obvious now, but at the time… not so much). An eerie silence fell as the entire facility, except for the lights, shut down.

After a moment of shocked disbelief (“What did you do!?”), Paul Tafforeau, who is Tanya’s collaborator at the ESRF, recovered his composure and set about informing the authorities what had happened and getting everything back up and running again. He even forgave me (sort of) and no one came to haul me away.

Here’s Paul, with another set of Neanderthal teeth, these from a child.

Paul Tafforeau examines a set of Neanderthal teeth photo © Larry Engel, 2008

This fossil has a fascinating story, and one we’ll tell in the show, because it was the first Neanderthal fossil ever discovered, in 1829, long before Neanderthals were officially recognized and named, and long before Darwin suggested that humans had evolved.

We don’t yet know what Paul and Tanya found out from the scans. That’s going to take several months of careful growth ring counting and analysis. But we do know they were happy with the images they got, and that by the time we get to putting together our program, they’ll be able to tell us how quickly these Neanderthal children grew up.

Next we’re off to the University of Oregon in Eugene, where we’ll find out what parts of Alan’s brain provide him with a couple of uniquely human skills – his facility with language, and the ability to use a screwdriver….

I just hope there are no big red buttons.