Name: Where Did Life Come From? (feat. PBS Space Time and Eons!)
Uploaded: 2021-05-04T09:15:40.000Z
Duration: 13 min 40 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Some people would argue the most important year in the history of soup was 1962, when

Andy Warhol released his soup-er soupy pop art.

But I think soup's best year came a decade earlier, in 1952, when a scientist named Stanley

Miller's experiment took some simple chemicals, like those found on early Earth, bubbled them

up through a tube, zapped them with electricity, and after a few days, floating in this soup,

he found amino acids–the building blocks of proteins, and one of the essential ingredients

This idea–that life's origins could be found in a puddle of chemicals–is an old

In the 1920s, two different scientists theorized about life arising from what they called a

And this soupy speculation even goes back (unsurprisingly) to Charles Darwin, who in

1871 wondered if life may have formed from chemicals “…in some warm little pond…”

What made Miller's experiment so special was it gave us proof: regular non-life stuff

could become cool life stuff super-easily.

But… everything “living” we see today, even the most basic bacteria, is so complex,

built of such intricate machinery, it's impossible to imagine they just popped into

We're going to go on a journey in search of the origin of life, and along the way there

will be a few forks in the road, maybe a couple speedbumps, and we're going to need help

We'll come to see that Miller's primordial soup isn't exactly how this story began.

But the FIRST question we should ask isn't how life started, it's when.

Life on Earth couldn't exist before Earth existed, and it formed around four and a half

billion years ago, at the dawn of the Hadean Era/Eon.

Soon after that, another planet collided with the young Earth, melted the entire crust,

After the crust cooled, there was even some liquid water… at least for a little while.

Because for the next couple hundred million years, Earth was showered with hundreds of

The oceans boiled away, the crust melted again, and Earth was basically no place for life…

until things settled down about 4 billion years ago, at the dawn of the Archean Eon.

This is the earliest possible time that life could have started on Earth, the beginning

of what we call the habitability boundary.

And fossil and chemical evidence tell us that early microbes existed by 3.7 billion years

ago, what's known as the biosignature boundary.

At some moment in here, non-life became life: we call this abiogenesis.

Therefore we can't go back and find that exact moment.

This brings us to the next big question on this journey… what is life?

You'd think biology would have a good definition for life, the thing it studies.

But as a biologist I can tell you this is much harder than it sounds.

In one chapter of biologist JBS Haldane's 1949 book What Is Life? he literally writes

“I am not going to answer this question.”

Life is a board game, a delicious breakfast cereal, and a highway?

According to the dictionary, it's the time between birth and death.

But none of these definitions really help us.

I think we might be asking the wrong question, because life isn't a thing that things have,

In school, many people learn a checklist for the characteristics a thing must have in order

But this list came from looking at life as we know it today.

Life at the very beginning was probably much simpler.

A physicist, Erwin Schrödinger, looked at all these things that life does and saw something

According to the second law of thermodynamics,  . But inside of living cells there's a

In 1944, Schrödinger defined life as a struggle against entropy– the persistent resistance

of decay, the preservation of DISequilibrium.

Since then we're learned a lot more about entropy, and it may be that the rise of complexity

Life creates these little closed systems where it works to keep things nice and ordered.

But this definition still leaves out one important thing: Living things evolve.

Inside the very first living things must have been molecules–chains of atoms–that carried

information–instructions for building things or codes for doing stuff.

Those molecules must have copied and made more of themselves, some a little different

And a few of those codes and instructions must have been better at doing whatever they

did, so they made even more of themselves.

What we're describing is evolution by natural selection, Darwin's famous idea, and for

life to move forward, it must have been there from the beginning.

With all this in mind, maybe we're finally able to come up with a better definition:

Life began the moment that molecules of information started to reproduce and evolve by natural

And now that we have a definition we can make some rules for what something

A living thing must work to avoid decay and disorder

To do that, a living thing has to create a closed system, or be made of cells

They have some molecule that can carry information about how to build cell machinery

This information must evolve by natural selection Sounds pretty good, but rules are one thing.

The ultimate question is how would this actually happen?

What would it require for these things to arise?

And–most importantly–how likely are each of these steps based on what we know from

Today, no matter where we look on the tree of life, most cell machinery is made of protein–

When modern cells make proteins, they copy genes from DNA into RNA and then use that

RNA as a blueprint for making the proteins.

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Where Did Life Come From? (feat. PBS Space Time and Eons!)

stuff

massive

bunch

journey