Name: Why Scurvy Shouldn't Exist
Uploaded: 2019-09-21T11:13:00.000Z
Duration: 5 min 46 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

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Adverbs of manner

When you hear the word “scurvy,” you probably think of

and if it's not treated, it can be deadly.

It's not just a thing of the past, either.

Scurvy still shows up in developing nations,

Thankfully, it is relatively easy to treat —

all you need is a high dose of Vitamin C.

nobody would have ever gotten scurvy in the first place.

The reason Vitamin C cures scurvy is because

the disease is actually caused by a Vitamin C deficiency.

Without this vitamin, the body can't properly form collagen.

the vast majority of our connective tissues,

so without enough of it, things can go seriously wrong.

For example, scurvy patients can develop skin

that's thin and fragile, where any wounds they get

That can make them more likely to contract a life-threatening infection.

Scurvy can also cause the collagen supporting

blood vessels to fall apart, which can lead to hemorrhages.

To be clear, this vitamin isn't the only thing we need to make collagen.

But it is the only component of the collagen

synthesis process our bodies can't naturally produce.

and why a high dose of it can cure the disease.

But what's interesting is that most of nature doesn't have to deal with this.

Lots of animals can make their own Vitamin C

Our very distant primate ancestors could do this, too.

the branch of primates that now includes humans

More specifically, we lost the ability to make an enzyme called GULO.

Just like with collagen, the process of making

When you look at different animals' genomes,

you'll see that most animals have the gene that codes for this enzyme.

Like, rabbits pump out way more GULO enzymes

during the winter months when Vitamin C-rich foods

are in short supply, and goats can really crank it out

Even animals toward the bottom of the evolutionary tree,

like sponges and jellyfish, have the gene

guinea pigs, some bats and birds, most fish...

So in our evolutionary past, our very distant ancestors

had the ability to make GULO and therefore Vitamin C.

But somewhere in primate evolution, a random mutation broke it.

This might seem more than a little unfair,

but you have to remember, mutations are random.

Most of the time, they're harmless and unnoticeable,

but sometimes they affect an important gene.

And when they do… well, it just kind of stinks.

because its gene is actually still in our genetic code —

although these days, it's just something called a pseudogene.

that accumulated enough mutations that it can't

perform its original job — or in the case of the GULO gene,

accumulated enough that it's totally nonfunctional.

Pseudogenes actually crop up all the time,

and the GULO gene is one of about 20,000 others in our genome.

For reference, we have about 27,000 genes

that actually make what they're supposed to.

So, you know… our genomes are kind of a mess.

But that's a little beside the point here.

The real question is, why did the nonfunctional

GULO gene get passed down in the first place?

After all, we can literally die without Vitamin C.

So it seems like the first primates to get this

broken gene should have died before they could pass it along to their offspring.

and they've come up with a hypothesis about what happened.

A part of it could be that there is some benefit to ditching the GULO gene.

byproduct of its reaction, which can form particles

called free radicals when it breaks down.

Subtitles ListPlay Video

Why Scurvy Shouldn't Exist

process

eliminate

cultivate

fragile