It Was Not Sugar. It Was Bread.

Look at a hunter-gatherer jaw from thirty thousand years ago and the striking thing is not that the teeth are straight, though they are.

It’s that there are no holes in them.

The numbers are not close

Skeletal populations from before agriculture show cavity rates that would be considered impossible today — commonly under 2 percent of teeth affected, in some samples effectively zero.

Then farming arrives, and the rate climbs. Not gradually, and not by a little. Neolithic farming populations show rates several times higher than the foragers who preceded them in the same regions.

And there is a second jump, much later, with industrialization and refined flour and cheap sugar, which takes it to where we are now.

Two steps, thousands of years apart, and the popular story only knows about the second one.

Which means sugar is not the origin

Refined sugar was a luxury good in Europe until the sixteenth century and a mass commodity only after industrial cane and beet production. The cavity rate had already risen dramatically long before any of that.

So what changed at the Neolithic transition?

Cooked starch.

Salivary amylase begins breaking down starch the moment it enters the mouth, and the product is glucose. Bread, porridge and gruel therefore deliver sugar to the teeth without anybody adding any.

More importantly, they deliver it stickily and continuously. Cooked starch adheres to enamel and sits in the fissures of molars, which means a much longer acid exposure than an equivalent amount of fruit sugar swallowed quickly.

The bacteria that cause cavities do not have a preference between table sugar and the glucose released from a piece of flatbread. They have a preference for fermentable carbohydrate sitting on a tooth, and farming supplied that for the first time in human history.

The bacteria themselves changed

This is the part that turns the story from inference into evidence.

Dental calculus fossilizes. Hardened plaque on ancient teeth traps the DNA of the bacteria that were living in it, and it survives for millennia.

Sequencing that material across the Neolithic transition shows the composition of the oral microbiome shifting — the mix moving toward acid-producing species associated with caries and away from the more diverse populations found in foragers.

And it shifts again at the industrial revolution, with Streptococcus mutans — the organism most associated with cavities — becoming dominant in a way it had not previously been.

So the change is not only what people ate. It is who was living in their mouths, and the diet selected for it.

But their teeth were not better

The romantic version of this needs correcting, because the failure mode simply moved.

Wear was catastrophic. Stone-ground flour carries grit, and unprocessed food requires far more chewing. Ancient chewing surfaces are frequently worn flat to the dentin, sometimes into the pulp — which produced exposed nerves and abscesses with no treatment available.

Gum disease was widespread. Bone loss around teeth is common in these populations, and there was no cleaning of any consequence.

Abscesses killed people. With no antibiotics, an infection that spread from a worn-through tooth was a plausible cause of death, and skulls show the bone destruction to prove it.

So: fewer cavities, more wear, more infection, and no way to fix any of it. Not a better mouth — a different one, failing differently.

And their jaws did fit

The one thing they genuinely had that we don’t is space.

Pre-agricultural skulls show full arches with all four wisdom teeth erupted and functional, and little crowding. Impaction is rare enough in those samples to be notable.

The reason isn’t tooth size — teeth have barely changed. The jaw grew larger under mechanical load. Bone develops in response to force, and a childhood of chewing tough, unprocessed food produces a longer, wider arch than a childhood of soft cooked food does.

Which is why crooked teeth are a modern condition rather than a modern flaw in people. The teeth arrive on the ancestral schedule into a shorter arch.

What actually follows from it

Two things, and neither is “eat like a caveman.”

Frequency matters more than quantity. The Neolithic problem was not the amount of carbohydrate but its persistence on the tooth. That maps directly onto now: six separate snacks do more damage than one dessert, because enamel dissolves during exposure and recovers between. Fewer separate eating events is the single biggest dietary lever available.

And starch counts. People carefully avoiding sugar while eating crackers, bread and crisps through the afternoon are running the Neolithic experiment on themselves. The bacteria cannot tell the difference, and the sticky version is worse.

The short version

Cavity rates were near zero before farming, jumped with bread, and jumped again with industrial sugar. Two steps, and the first one is the one nobody knows about.

Cooked starch becomes glucose in your mouth, sticks to the tooth, and feeds the same bacteria sugar does. The bacteria themselves changed to suit.

And those mouths were not healthier. They were worn flat, infected, and untreatable — with beautifully straight teeth and no holes in them.