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Around 10 million years ago, one of our primate
ancestors was searching for food on a forest
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floor.
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This primate was one of the last common ancestors
of humans, gorillas and chimpanzees—and
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it was slowly adapting to a new way of life,
splitting its time between the trees and the
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ground.
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And this lifestyle opened up all kinds of
opportunities for finding food -- like scavenging
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fruits that had fallen from the trees.
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But some of these new foods could hold some
surprises.
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Once they landed on the ground, the fruits
often acquired a little kick.
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This happened through the process of fermentation.
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Bacteria or yeast got into the fruit and started
feasting, converting the fruit’s carbohydrates
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into new chemicals, including ethanol - a
kind of alcohol.
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But thanks to a recent adaptation, instead
of getting sick from the boozy, fermented
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fruits, that primate could digest them safely,
and get more calories at the same time.
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This new superpower would open up a whole
new nutritional landscape for us: fermented
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foods.
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It took millions of years for hominins to
go from enjoying nature’s own fruit punch
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to making things like kimchi and beer.
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But figuring out how that process unfolded
has required a lot of scientific sleuthing.
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Since these foods don’t leave much of a
trace in the fossil record, scientists have
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had to rely on a whole bunch of different
disciplines -- from genetics to experimental
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archaeology -- to solve the mystery of our
relationship with fermentation.
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And it turns out, the very evolutionary path
of our species may have been shaped, at least
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in part, by the delicious chemistry of fermentation.
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On the most basic level, fermentation is simply
when microbes metabolize certain foods.
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Yeast and bacteria, for example, eat a lot
of the same things we do.
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They use enzymes to digest their food, and
what they leave behind are byproducts of that
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process.
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Now, we’re used to thinking of fermentation
in terms of things like bread or cheese or
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wine, but it can happen to pretty much any
kind of food molecule: carbohydrates, lipids,
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even proteins.
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Fruits, vegetables, grains, fish, red meat—they’re
all fair game as far as microbes are concerned.
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And hominins have benefited from this process
when certain microbes have gotten into our
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food first and produced the right byproducts.
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For example, lactic acid bacteria are some
of the most common microbes found in fermented
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foods today, like sourdough bread and cheese.
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When those bacteria get to work, they produce
lactic acid.
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And the acidic environment that they create
keeps other, more dangerous microbes from
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getting into the food.
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The same thing happens when microbes produce
ethanol, also known as alcohol; the alcohol
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helps make the environment around the food
inhospitable to harmful bacteria.
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So, humans didn’t invent fermentation.
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We just took advantage of the work the microbes
were already doing, and eventually figured
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out how to harness that work to make foods
that we wanted and that were safer to eat.
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But for our ancestors, fermented food probably
seemed pretty … kinda dicey.
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For example, let’s go back to that fruit
on the forest floor.
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When our primate ancestors started eating
fermented fruits, the ethanol in them could’ve
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posed a big problem.
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Instead of just getting the sugars and starches
they were used to, now they were absorbing
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alcohol, too.
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And if their bodies couldn’t digest it,
the ethanol could’ve quickly made them sick.
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Sort of like getting a bad hangover, but after
only a few sips of booze.
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Luckily for these primates, they acquired
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the ability to metabolize ethanol much more
efficiently than others had in the past.
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A random genetic mutation led to a change
to a digestive enzyme known as ADH4 that shows
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up in huge amounts on the tongue, and in the
esophagus and stomachs of primates.
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And this new version of ADH4 was 40 times
better at digesting ethanol - which meant
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a new source of calories was suddenly available
that didn’t pose the risk of getting sick.
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Ok but eating fruit that’s
fallen on the ground, that's one thing
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But what about drinking milk that’s
gone sour or eat meat that’s kinda rotten.
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How could either of those things be appetizing?
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Welp, some researchers think it has to do
with how our sense of taste evolved.
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When our hominin ancestors were hunting and
gathering to get their food, their sense of
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taste was crucial for identifying which foods
might be safe and which might be dangerous.
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And the price of being wrong could be pretty
high, like we talked about in our episode
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about what real paleo diets were like.
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Today, human taste buds interpret different
foods as being sweet, salty, sour, bitter
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or umami —which is a savory flavor.
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Sweet and salty flavors come from nutritious
or calorie-dense sources, so we tend to seek
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those foods out.
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Take carbohydrates, which can often taste
sweet.
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Carbs aren’t just the main source of calories
in bread and breakfast cereals—they also
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account for the calories in fruits like bananas
or vegetables like yams.
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As for salty foods, some researchers think
that we seek them out because we sweat and
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lose sodium, so we need more of them.
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And then there are bitter flavors, which have
helped us interpret that taste as a warning
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that something might be poisonous.
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That’s because most compounds that produce
a bitter flavor—like those in milkweed plants
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—are toxic at different concentrations.
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But maybe the weirdest taste adaptation we
have is the ability to taste sourness.
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Most chemicals that produce sour flavors don’t
have much nutritional value—like, say, vinegar.
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But!
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Foods that have been fermented or are rich
in vitamin C are often sour too!
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So it’s possible that our ability to taste
sour foods helped us identify fermented foods
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specifically, because those foods added important
nutrients to our diet.
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Finally, our preference for that hard-to-define
flavor known as umami might also be related
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to fermentation.
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Today, the flavor is usually associated with
things like cooked meat, and fermented products,
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like miso and soy sauce.
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But raw meat doesn’t have that umami flavor.
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Plus, it requires more energy to chew and
digest than cooked meat.
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So it’s been suggested that our preference
for umami might’ve evolved in response to
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the nutritional benefits of eating foods that
microbes had already pre-digested for us.
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The flavor was a signal that microbes had
already done some of the work.
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And just like our ability to taste sweetness,
our taste receptors for umami seem to have
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deep evolutionary roots and are shared by
most land vertebrates.
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Ok but
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Still, the idea of letting microbes digest
meat before we get to it sounds like a recipe
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for food poisoning, right?
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But in the proper conditions, this type of
fermentation can actually be beneficial.
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Some researchers think that our distant relatives,
Homo erectus, may have been eating fermented
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meat—though there’s not any concrete archaeological
evidence for this.
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But it’s possible, because fermented foods
didn’t require specific tools for their
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preparation.
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Homo erectus literally would’ve just had
to stash the meat somewhere and wait.
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For example, we know that fermentation can
happen if meat is buried, or submerged in
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water.
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In fact, one paleontologist in the 1990s demonstrated
this in a pretty convincing, if kinda odd
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way, by submerging a dead horse in a pond
in late winter.
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And sure enough, between the cold and the
low-oxygen environment at the bottom of the
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pond, by spring the horse meat was … sour,
and “cheesy smelling,” but also totally
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free of pathogens and safe to eat!
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I am so hungry right now
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So anyway, it’s at least possible that techniques
like this could’ve been used by human ancestors
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and relatives, including Neanderthals.
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Thanks to a number of archaeological sites
associated with Neanderthals, scientists think
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they ate a lot of meat.
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And it wasn’t just scavenged meat—the
animals were mostly adults and showed evidence
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of being butchered.
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So the assumption was that Neanderthals were
big time carnivores, relying on meat for fat
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and protein.
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But an anthropologist named John Speth was
puzzled over how they avoided getting scurvy.
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This is a disease that happens when we don’t
get enough vitamin C. It’s killed millions
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of people throughout history and can still
be a problem today.
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Neanderthals couldn’t exactly have gone
to a corner store to get some lime to squeeze
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on those rhino ribs or whatever
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Plus vitamin C is one of the most unstable
vitamins.
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It’s easily leached out of foods by water,
and it quickly breaks down when exposed to
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oxygen, heat, light, and elevated pH levels.
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Now, the only places where vitamin C is found
in most animals’ bodies are the organs,
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including the brain.
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So if Neanderthals were eating a lot of meat,
and the vitamin C in animal organs degenerates
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when it’s cooked or exposed to oxygen, how
did they get their vitamin C?
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Speth had a hypothesis: maybe the Neanderthals
were fermenting the meat.
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This would’ve preserved the vitamin C, while
also making the meat easier to digest without
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needing to cook it.
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If the Neanderthals had stashed those meats
somewhere for safekeeping, that might’ve
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protected the fermenting meat from oxygen
exposure, so the vitamin C would’ve been
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more stable.
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But would they have gotten sick from eating
something that was, kind of rotten?
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Maybe not.
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Speth pointed out that there are a number
of cultures today that have been fermenting
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meat for centuries, like the Inuit, who bury
meat in pits lined with acidic leaves.
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The leaves, along with the acid produced by
fermentation, make it difficult for dangerous
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bacteria, like the ones that cause botulism,
to survive.
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As Homo sapiens spread around the world and
explored new environments, fermentation came
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to play an even greater role in our relationship
with food.
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It even figures into one of the biggest questions
in anthropology: Did we start practicing agriculture
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so that we could bake bread—or so that we
could brew beer?
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Don't make me choose!
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The earliest evidence of brewing comes from
a burial site in Israel, which has been dated
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to 13,700 years ago.
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And the burials include several mortars—stones
that had been hollowed out for grinding and
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storing foods.
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And researchers found starches in the mortars
that showed signs of having been mashed and
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fermented.
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So the people who made those mortars were
making alcohol!
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Whatever drink it was, was probably very low
in alcoholic content, but it’s still considered
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the earliest known evidence of making fermented
beverages.
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Since then, fermentation has become a fundamental
part of the human diet.
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We’ve fermented dairy products into cheese
and yogurt, grains and grapes into alcohol,
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vegetables into pickles and kimchi, and even
eggs and meat.
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Fermented foods give us access to vitamin
C, to bacteria that help with digestion, and
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make some foods easier to digest, so our bodies
don’t have to work as hard to convert them
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into energy.
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So a lot of who you are has been informed
by our ancestors’ complex and sometimes
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risky relationship with fermented foods, going
back to that primate ancestor some 10 million
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years ago.
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It's in your tongue, in your brain,
in your gut and in your DNA.
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So, cheers!
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So now that we’ve made you hungry, I guess, be sure
to watch our other human diet episode, “The
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Risky Paleo Diets of Our Ancestors”, and
for more on our evolution check out the “Human
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Evolution Learning Playlist”.
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Thanks to this month’s sweet Eontologists:
Lucan Curtis-Mahoney, Sean Dennis, Jake Hart,
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Jon Davison Ng, Patrick Seifert, and Steve!
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Pledged your support at patreon.com/eons and
become an Eonite.
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And as always thank you for joining me today
in the Konstantin Haase studio.
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Subscribe at youtube.com/eons to learn more
about our ancient past.
