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Practice English Speaking&Listening with: Blood types are a 20-million-year mystery

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- Do you know your blood type?

If you haven't been in any medical situations

where blood type is important, you might not.

I certainly don't, and I can't speak for everyone,

but most of my friends and family

said that they too had no idea.

My dad earned half a point for correctly answering red,

among other responses from my friends, like boiling.

And frozen.

But there's actually a lot of mystery around blood.

We know that there are eight main blood groups

that make up most of the world's population.

A, B, AB, and O.

And a negative and positive for each.

But it turns out that scientists still don't know why

we evolved different blood types.

And that may remain a mystery for a long time.

But for now, science can at least tell me a little bit

about my own blood.

(mysterious music)

That curiosity led me to buy this test.

It's called the EldonCard.

It's cheap, simple, and it takes just a few minutes

to determine your blood type.

All you have to do is prick your finger,

apply four drops of blood, and mix the samples

with the different serums.

Depending on how the samples agglutinate, or clump,

you can determine your blood type.

In developed parts of the world,

it's not crucial to know your blood type

off the top of your head.

Doctors will typically run tests before any major

procedure, and if there's any doubt in a medical

emergency, you'll most likely receive O negative blood.

That's the universal donor blood that's safe to give

to any A, B, AB or O recipient.

But what would happen if you received

the wrong type of blood?

Well, some curious minds found that out the hard way.

For thousands of years, nobody really understood blood.

A Greek doctor from 200 CE believed that it was created

from food and liver.

And this school of thought lived on for nearly 1500 years.

It wasn't until the early 17th century

that a British doctor named William Harvey

discovered that blood actually circulated through the body.

And this spawned a new age of experimentation with blood.

In 1665, an English physician successfully kept

one dog alive by transfusing it with the blood

of another dog.

But then things got kind of weird.

Just two years later, doctors began experimenting

with xenotransfusions.

That is, transfusing humans with animals' blood,

such as sheep.

And those human patients died.

It wasn't until 1900 that we finally realized people

and animals actually have different types of blood

that determine whose blood can mix with whose.

And that's where those different letters come into play.

If you're type A, your immune system will perceive

type B blood as an intruder, and trigger an auto-immune

response that can cause kidney failure,

extensive blood clotting, and even shock.

And the reverse is true of type B blood.

The immune system will attack type A.

AB blood, however, can accept both A and B blood

without triggering that auto-immune response.

Things start to get a little more complicated

when you introduce the rhesus factor,

or the negative and positive part of your blood type.

Positives can accept negatives, but the opposite

is extremely dangerous.

And to further complicate things, scientists have

discovered dozens of more blood types,

such as the Duffy blood group, which can determine

your susceptibility to malaria.

Or the Hh blood type, which 1 in 10,000

people in India have.

But the vast majority of humans

fall into this A, B, O system.

(mysterious music)

As for why humans evolved this complicated system

of blood types and compatibility, we don't really know.

The original mutations are thought to date back

nearly 20 million years.

But look, whatever the biology is behind blood typing,

it's a real, practical thing that matters.

And in many parts of the world, knowing your blood type

is fairly common knowledge.

In Japan, it's linked to your personality.

Sort of like a horoscope.

You can even add your blood type to your Facebook profile.

And in 2011, former Japanese minister of reconstruction

Ryu Matsumoto blamed his irritable and impetuous behavior

on his blood type, type B,

after he was forced to step down from his seat.

Personality types aside, I did this EldonCard test

because it's just not a bad idea to know your blood type.

If you're traveling somewhere that's rural,

or doesn't have access to advanced medicine,

it's good for you and your traveling companions to know

your types, just in case of an accident along the way.

And in a big emergency closer to home, blood banks often

put out calls for donors of a specific type.

And remember, if you're type O negative,

you're an extremely useful universal donor.

So, knowing your type can give you a little peace of mind.

And hey, if you're in Japan it's

a great way to break the ice.

Although, type Bs don't really have the best reputation.

But I'm fine, I'm A positive.

Hey everyone, just a note that you can also find

your blood type by donating blood, serving in the military,

or just by asking your doctor during routine blood work.

But the EldonCard is fun, and kind of do it yourself.

If you haven't already, please like, comment,

and subscribe to our new Verge Science YouTube channel,

where we're putting out a video every week.

Thank you.

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