Teeth.

They’re the coolest rocks  you’ll ever grow in your face. And I’m only half kidding,  because they basically are rocks made of millions of  tiny mineralized crystals.

But things get tricky when that mineral  degrades, because unlike bones or skin, your teeth can’t heal themselves. So when we get a cavity or hole in  our tooth, we need help fixing it. So you might be thinking that before  modern dentistry became a thing, people must’ve had even worse teeth,  rotting out of their heads left and right.

And yeah, while there are some gnarly  examples of ancient humans with cavities, they weren’t, like, eating candy by the handful and washing it down with energy drinks. At the same time, the story isn’t as  simple as “humans get a lot of cavities now that we eat processed foods”, either. So let’s take a peek back in time and figure out why humans have the worst  teeth in the animal kingdom. [♪ INTRO] The most common tooth problem in our  species is cavities, also known as caries.

Over 90% of us will get at least one  at some point in our adult lives, And the cause of this pesky  tooth decay is the presence of certain bacteria in our mouth, or  more precisely, in the dental plaque that builds up on the surface of our teeth. The bacterium Streptococcus mutans is  the main culprit, breaking down sugars in the food we eat, and creating  acidic byproducts in the process. And it’s those acids that  erode or weaken our enamel, making it susceptible to cavities.

There are other factors that play into  it too, like how much saliva you produce, whether you practice good dental  hygiene, or even your genetic makeup. But the biggest factor we  have to come back to is sugar. Now “sugar” can mean a lot of  things, and not just candy.   And it’s not just classic table  sugar that leads to cavities, but also starches found in foods  like bread, rice, and pasta.

Our love of sugary and starchy things  goes way back to before farming, and even before our species existed. Humans are primates, and our extinct ancestors and living relatives are mostly fruit-eaters. Since fruit is basically sugar plus  fiber, it’s not surprising that fossil primates from as long as 54 million  years ago had cavities in their teeth.

As do some fruit-loving  monkeys and apes alive today. Primates can definitely have a sweet tooth. There are chimps who eat huge amounts of fruit and like to chew and suck on wads  of fig gunk for hours on end.

And yet chimps only have something  like a 45% max cavity rate across individuals. which is half of the  90 plus percent in present-day humans. So when did things really pop  off for us, tooth decay-wise? Well the short answer is: The agricultural  revolution, around 10,000 BCE.

It happened at different  times all across the globe, but in general it caused massive dietary changes to the majority of people on Earth. Because before farming, people  hunted and gathered foods that grew wild in their environment. If we flash back to, say, 1.5 million years ago, early human relatives like Paranthropus robustus were eating different kinds of  plants, but not a ton of sugary stuff.

So it’s not surprising that even  though they had a few cavities, they had way fewer than the later-and-more-like-us Homo erectus from the same site. Neandertals had cavities,  too, but not many at all, despite the fact that they too carried  the Streptococcus mutans bacterium. We know that because some clever  scientists chipped off the hardened dental plaque from some Neandertal teeth and found DNA evidence of their microbiome inside.

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If we look at our own species,  Homo sapiens, we see variation in how many people were affected  by tooth decay, and groups that ate more sugary foods were usually  the ones with more cavities. Take a site in Morocco from  around 14 -15,000 years ago known as les Grotte des Pigeons. In a 2014 study, researchers found  that around half of the teeth and 94% of the people had cavities, similar  to modern industrialized populations.

Compare that to most other  hunter-gatherer societies, which at most have cavities  in like 15% of their teeth. But how could that happen without  gummy worms and Coca-Cola? Well, evidence suggests that they  ate a boatload of an especially sweet kind of acorn, that gets  soft and sticky when cooked, in addition to wild oats and legumes.

But the fun for Streptococcus mutans  and its cavity-making pals really got started when we figured out how  to farm grains like wheat and barley. And it got even worse with heavy  food processing and eventually, adding sugar to everything from  bread to sauces to fruit juice. We have plenty of evidence that shows  once farming was invented, people across the world had the potential to develop  roughly modern-day levels of cavities.

But we can also see evolution in  the cavity-causing bacterium itself that came along with our  changes in food production. While ancient human relatives have  been plagued by Streptococcus mutans since at least the Neandertal  days, there was a bump in the bacterium’s genetic  diversity around 10,000 BCE. These changes coincided with the  advent of farming, and more changes have happened in the last 750 years since  we started actively cultivating sugar.

Just like any good pathogen, it adapts  to get better and better at exploiting its environment and doing its evolutionary job. Which is… ruining our teeth. In fact, we might have to  start worrying about it again because it’s becoming resistant to antibiotics.

The story of us, our teeth, and  Streptococcus mutans is long, twisty, and far from over. But even though most of us will have  to deal with a cavity at some point in our lives, at least we will live  long enough to get them these days, which I can’t say was true  for many of the ancient people we talked about in this video. Tooth problems just come along with the territory, but it’s a small price to pay to be able  to eat handfuls of candy in my jammies. [♪ OUTRO]