floor.

This primate was one of the last common ancestors of humans, gorillas and chimpanzees—and

it was slowly adapting to a new way of life, splitting its time between the trees and the

ground.

And this lifestyle opened up all kinds of opportunities for finding food -- like scavenging

fruits that had fallen from the trees.

But some of these new foods could hold some surprises.

Once they landed on the ground, the fruits often acquired a little kick.

This happened through the process of fermentation.

Bacteria or yeast got into the fruit and started feasting, converting the fruit's carbohydrates

into new chemicals, including ethanol - a kind of alcohol.

But thanks to a recent adaptation, instead of getting sick from the boozy, fermented

fruits, that primate could digest them safely, and get more calories at the same time.

This new superpower would open up a whole new nutritional landscape for us: fermented

foods.

It took millions of years for hominins to go from enjoying nature's own fruit punch

to making things like kimchi and beer.

But figuring out how that process unfolded has required a lot of scientific sleuthing.

Since these foods don't leave much of a trace in the fossil record, scientists have

had to rely on a whole bunch of different disciplines -- from genetics to experimental

archaeology -- to solve the mystery of our relationship with fermentation.

And it turns out, the very evolutionary path of our species may have been shaped, at least

in part, by the delicious chemistry of fermentation.

On the most basic level, fermentation is simply when microbes metabolize certain foods.

Yeast and bacteria, for example, eat a lot of the same things we do.

They use enzymes to digest their food, and what they leave behind are byproducts of that

process.

Now, we're used to thinking of fermentation in terms of things like bread or cheese or

wine, but it can happen to pretty much any kind of food molecule: carbohydrates, lipids,

even proteins.

Fruits, vegetables, grains, fish, red meat—they're all fair game as far as microbes are concerned.

And hominins have benefited from this process when certain microbes have gotten into our

food first and produced the right byproducts.

For example, lactic acid bacteria are some of the most common microbes found in fermented

foods today, like sourdough bread and cheese.

When those bacteria get to work, they produce lactic acid.

And the acidic environment that they create keeps other, more dangerous microbes from

getting into the food.

The same thing happens when microbes produce ethanol, also known as alcohol; the alcohol

helps make the environment around the food inhospitable to harmful bacteria.

So, humans didn't invent fermentation.

We just took advantage of the work the microbes were already doing, and eventually figured

out how to harness that work to make foods that we wanted and that were safer to eat.

But for our ancestors, fermented food probably seemed pretty … kinda dicey.

For example, let's go back to that fruit on the forest floor.

When our primate ancestors started eating fermented fruits, the ethanol in them could've

posed a big problem.

Instead of just getting the sugars and starches they were used to, now they were absorbing

alcohol, too.

And if their bodies couldn't digest it, the ethanol could've quickly made them sick.

Sort of like getting a bad hangover, but after only a few sips of booze.

Luckily for these primates, they acquired

the ability to metabolize ethanol much more efficiently than others had in the past.

A random genetic mutation led to a change to a digestive enzyme known as ADH4 that shows

up in huge amounts on the tongue, and in the esophagus and stomachs of primates.

And this new version of ADH4 was 40 times better at digesting ethanol - which meant

a new source of calories was suddenly available that didn't pose the risk of getting sick.

Ok but eating fruit that's fallen on the ground, that's one thing

But what about drinking milk that's gone sour or eat meat that's kinda rotten.

How could either of those things be appetizing?

Welp, some researchers think it has to do with how our sense of taste evolved.

When our hominin ancestors were hunting and gathering to get their food, their sense of

taste was crucial for identifying which foods might be safe and which might be dangerous.

And the price of being wrong could be pretty high, like we talked about in our episode

about what real paleo diets were like.

Today, human taste buds interpret different foods as being sweet, salty, sour, bitter

or umami —which is a savory flavor.

Sweet and salty flavors come from nutritious or calorie-dense sources, so we tend to seek

those foods out.

Take carbohydrates, which can often taste sweet.

Carbs aren't just the main source of calories in bread and breakfast cereals—they also

account for the calories in fruits like bananas or vegetables like yams.

As for salty foods, some researchers think that we seek them out because we sweat and

lose sodium, so we need more of them.

And then there are bitter flavors, which have helped us interpret that taste as a warning

that something might be poisonous.

That's because most compounds that produce a bitter flavor—like those in milkweed plants

—are toxic at different concentrations.

But maybe the weirdest taste adaptation we have is the ability to taste sourness.

Most chemicals that produce sour flavors don't have much nutritional value—like, say, vinegar.

But!

Foods that have been fermented or are rich in vitamin C are often sour too!

So it's possible that our ability to taste sour foods helped us identify fermented foods

specifically, because those foods added important nutrients to our diet.

Finally, our preference for that hard-to-define flavor known as umami might also be related

to fermentation.

Today, the flavor is usually associated with things like cooked meat, and fermented products,

like miso and soy sauce.

But raw meat doesn't have that umami flavor.

Plus, it requires more energy to chew and digest than cooked meat.

So it's been suggested that our preference for umami might've evolved in response to

the nutritional benefits of eating foods that microbes had already pre-digested for us.

The flavor was a signal that microbes had already done some of the work.

And just like our ability to taste sweetness, our taste receptors for umami seem to have

deep evolutionary roots and are shared by most land vertebrates.

Ok but

Still, the idea of letting microbes digest meat before we get to it sounds like a recipe

for food poisoning, right?

But in the proper conditions, this type of fermentation can actually be beneficial.

Some researchers think that our distant relatives, Homo erectus, may have been eating fermented

meat—though there's not any concrete archaeological evidence for this.

But it's possible, because fermented foods didn't require specific tools for their

preparation.

Homo erectus literally would've just had to stash the meat somewhere and wait.

For example, we know that fermentation can happen if meat is buried, or submerged in

water.

In fact, one paleontologist in the 1990s demonstrated this in a pretty convincing, if kinda odd

way, by submerging a dead horse in a pond in late winter.

And sure enough, between the cold and the low-oxygen environment at the bottom of the

pond, by spring the horse meat was … sour, and “cheesy smelling,” but also totally

free of pathogens and safe to eat!

I am so hungry right now

So anyway, it's at least possible that techniques like this could've been used by human ancestors

and relatives, including Neanderthals.

Thanks to a number of archaeological sites associated with Neanderthals, scientists think

they ate a lot of meat.

And it wasn't just scavenged meat—the animals were mostly adults and showed evidence

of being butchered.

So the assumption was that Neanderthals were big time carnivores, relying on meat for fat

and protein.

But an anthropologist named John Speth was puzzled over how they avoided getting scurvy.

This is a disease that happens when we don't get enough vitamin C. It's killed millions

of people throughout history and can still be a problem today.

Neanderthals couldn't exactly have gone to a corner store to get some lime to squeeze

on those rhino ribs or whatever

Plus vitamin C is one of the most unstable vitamins.

It's easily leached out of foods by water, and it quickly breaks down when exposed to

oxygen, heat, light, and elevated pH levels.

Now, the only places where vitamin C is found in most animals' bodies are the organs,

including the brain.

So if Neanderthals were eating a lot of meat, and the vitamin C in animal organs degenerates

when it's cooked or exposed to oxygen, how did they get their vitamin C?

Speth had a hypothesis: maybe the Neanderthals were fermenting the meat.

This would've preserved the vitamin C, while also making the meat easier to digest without

needing to cook it.

If the Neanderthals had stashed those meats somewhere for safekeeping, that might've

protected the fermenting meat from oxygen exposure, so the vitamin C would've been

more stable.

But would they have gotten sick from eating something that was, kind of rotten?

Maybe not.

Speth pointed out that there are a number of cultures today that have been fermenting

meat for centuries, like the Inuit, who bury meat in pits lined with acidic leaves.

The leaves, along with the acid produced by fermentation, make it difficult for dangerous

bacteria, like the ones that cause botulism, to survive.

As Homo sapiens spread around the world and explored new environments, fermentation came

to play an even greater role in our relationship with food.

It even figures into one of the biggest questions in anthropology: Did we start practicing agriculture

so that we could bake bread—or so that we could brew beer?

Don't make me choose!

The earliest evidence of brewing comes from a burial site in Israel, which has been dated

to 13,700 years ago.

And the burials include several mortars—stones that had been hollowed out for grinding and

storing foods.

And researchers found starches in the mortars that showed signs of having been mashed and

fermented.

So the people who made those mortars were making alcohol!

Whatever drink it was, was probably very low in alcoholic content, but it's still considered

the earliest known evidence of making fermented beverages.

Since then, fermentation has become a fundamental part of the human diet.

We've fermented dairy products into cheese and yogurt, grains and grapes into alcohol,

vegetables into pickles and kimchi, and even eggs and meat.

Fermented foods give us access to vitamin C, to bacteria that help with digestion, and

make some foods easier to digest, so our bodies don't have to work as hard to convert them

into energy.

So a lot of who you are has been informed by our ancestors' complex and sometimes

risky relationship with fermented foods, going back to that primate ancestor some 10 million

years ago.

It's in your tongue, in your brain, in your gut and in your DNA.

So, cheers!

So now that we've made you hungry, I guess, be sure to watch our other human diet episode, “The

Risky Paleo Diets of Our Ancestors”, and for more on our evolution check out the “Human

Evolution Learning Playlist”.

Thanks to this month's sweet Eontologists: Lucan Curtis-Mahoney, Sean Dennis, Jake Hart,

Jon Davison Ng, Patrick Seifert, and Steve!

Pledged your support at patreon.com/eons and become an Eonite.

And as always thank you for joining me today in the Konstantin Haase studio.

Subscribe at youtube.com/eons to learn more about our ancient past.