Around 10 million years ago, one of our primate
ancestors was searching for food on a forest
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.
