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May 20th, 2009
Spark Blog: Video: Ancient Dental Cleaning

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

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