This Is What All Life is Made Of | Cell | BBC Earth Science

Summary

The script narrates the groundbreaking journey of scientific discovery, from Theodore Schwann's identification of cells as the building blocks of life to the revelation of DNA's structure by Watson and Crick. It explores the pioneering work of early microscopists, the innovative experiments of scientists like Misha, and the astonishing findings of astrobiologists, suggesting that the origins of life may lie beyond Earth. The narrative weaves together the theories of evolution and cell biology, culminating in the understanding that all life on Earth may have descended from a single common ancestor.

Takeaways

• 🌟 Theodore Schwann's innovative staining techniques and use of advanced microscopes led to the discovery of cells in animal tissues, challenging the notion that animal tissues were fundamentally different from plants.
• 🔬 The field of anatomy was in disarray with no unified understanding of what animals or humans were made of, until Schwann's work contributed to the unification of animal and vegetable biology through the cell theory.
• 🏛️ Berlin, being the European Center for Anatomy, was a hub for brilliant biologists, providing an ideal environment for Schwann to make his groundbreaking discoveries.
• 👀 Antonie van Leeuwenhoek's simple yet powerful microscope revolutionized the way we see the world, allowing for the magnification of objects up to 500 times, a feat not replicated for over a century.
• 💧 Van Leeuwenhoek's curiosity led him to examine water, discovering microorganisms within, which was a fundamental breakthrough in understanding the composition of life.
• 🧬 Friedrich Meischer's experiments with white blood cells and pepsin led to the isolation of a new molecule in the cell nucleus, which he named 'nuclein', now known as DNA.
• 🔬 Rosalind Franklin's expertise in X-ray imaging at King's College was pivotal in capturing the clearest images of DNA, which were instrumental in revealing its structure.
• 🎓 James Watson and Francis Crick used Franklin's Photo 51 to deduce the double helix structure of DNA, propelling them to scientific fame and bringing the cell to the center of global scientific attention.
• 🌀 The discovery of the DNA double helix and the specific base pairing of A-T and C-G provided the mechanism for genetic replication, a fundamental concept in biology.
• 📚 Charles Darwin's 'Origin of Species' introduced the theory of evolution by natural selection, suggesting that all life on Earth descended from a single common ancestor.
• 🚀 Modern astrobiology has discovered extraterrestrial organic molecules within meteorites, suggesting that the building blocks of life may have an extraterrestrial origin.

Q & A

Who was Theodore Schwann and what is his contribution to biology?

Theodore Schwann was a young and ambitious scientist in Berlin who is credited with the discovery of cells in animals. He used innovative staining techniques and a Lister-style microscope to identify the cellular structure in various animal tissues, leading to the unification of animal and vegetable biology under the cell theory.

What was the state of the field of anatomy before Schwann's discovery?

Before Schwann's discovery, the field of anatomy was in a state of chaos. Researchers believed that animals and humans were made up of various structures like granules, fibers, tubes, globules, and bladders, with no clear understanding of the importance of cells in biological systems.

How did the invention of the microscope contribute to the understanding of cells?

The invention of the microscope, particularly by Antonie van Leeuwenhoek, revolutionized the understanding of cells. Van Leeuwenhoek's microscope, with its simple yet powerful lens, allowed for the magnification of objects up to 500 times, enabling him to observe microorganisms in water and lay the foundation for the discovery of cellular structures.

What role did the city of Berlin play in the advancement of biology during Schwann's time?

Berlin was the European Center for Anatomy during Schwann's time, attracting the most brilliant biologists. It was home to the prestigious Anatomical Museum where Schwann took a position, contributing to the city's role in the advancement of biological sciences.

What was the significance of the double helix model of DNA proposed by Crick and Watson?

The double helix model of DNA proposed by Crick and Watson was significant because it revealed the structure of DNA, showing how genetic information is stored and replicated. This model explained the pairing of the four nucleotide bases (A, T, C, G) and how DNA replication occurs, which is fundamental to understanding the basis of life.

How did Rosalind Franklin contribute to the discovery of the DNA structure?

Rosalind Franklin was an expert in X-ray imaging and took over 100 pictures of DNA strands using a specially built camera. Her photo 51 provided the clearest image of DNA, showing the distinctive X shape that was key to revealing the structure of the DNA molecule.

What was the significance of the discovery of DNA by Friedrich Miescher?

Friedrich Miescher's discovery of DNA was significant because he identified a new molecule made up of carbon, hydrogen, oxygen, nitrogen, and phosphorus, which he found in the nucleus of cells. This molecule, which he called 'nuclein' and is now known as DNA, was present in all lifeforms, marking the beginning of genetic science.

How did Charles Darwin's theory of evolution relate to the cell theory?

Charles Darwin's theory of evolution by natural selection and the cell theory, which states that all living things are made up of cells, can be combined to suggest that all life on Earth evolved from a single common ancestor. This idea supports the concept that all organisms share a common cellular basis for life.

What was the content of Darwin's letter to Joseph Hooker regarding the origins of life?

In his letter to Joseph Hooker, Darwin hypothesized that life on Earth may have begun in a 'warm little pond' with various chemicals, light, heat, and electricity, leading to the formation of a protein compound that could undergo further complex changes. This idea suggested a chemical origin of life without the need for a creator.

What evidence suggests that components of our genetic code may have an extraterrestrial origin?

Analysis of the Murchison meteorite, which is nearly as old as the solar system, revealed the presence of extraterrestrial organic molecules, including a component of our genetic code. This discovery suggests that some of the building blocks for life on Earth may have originated from outer space.

Outlines

00:00

🔬 The Unification of Cell Theory and the Discovery of Theodore Schwann

This paragraph introduces the historical context of cell theory's development, highlighting Theodore Schwann's pivotal role. Set in Berlin, a hub for anatomy, Schwann's innovative staining techniques and use of advanced microscopes led to the discovery of cellular structures in various animal tissues. The narrative discusses the chaotic state of anatomy at the time and the significant gap between botany and zoology due to the difficulty in observing animal cells. Schwann's findings eventually contributed to the understanding that cells are the fundamental units of all life forms, challenging the prevailing notion that animal tissues were fundamentally different from plants.

05:02

🔬 Van Leeuwenhoek's Microscopic Revolution and the Study of DNA

The paragraph delves into the contributions of Antonie van Leeuwenhoek, who crafted a powerful microscope that allowed for the magnification of objects up to 500 times. His curiosity led him to examine various subjects, including water, which he hypothesized contained undiscovered entities. Van Leeuwenhoek's work laid the foundation for future discoveries in biology. The narrative then shifts to the study of white blood cells by an unnamed individual (referred to as 'Misha' in the next paragraph), who used the chaos of war and the abundance of pus-filled bandages as a resource for his experiments. This individual's innovative approach to isolating the cell nucleus involved the use of pepsin, an enzyme found in a pig's stomach, to digest the cell's cytoplasm, leaving the nucleus for study.

10:05

🧬 The Discovery of DNA and its Role in the Chemistry of Life

This section focuses on the discovery of DNA by a scientist named Misha, who analyzed the chemical composition of the cell nucleus. He identified a unique molecule composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus, which he termed 'nuclein' and is now known as DNA. Misha's experiments with various sperm cells from different species consistently revealed the presence of this molecule, suggesting its universality in living organisms. The narrative also touches upon Rosalind Franklin's critical role in capturing X-ray images of DNA at King's College, which were instrumental in understanding its structure. However, it was James Watson and Francis Crick who are famously associated with the discovery of DNA's structure, despite Franklin's significant contributions.

15:08

🌀 The Double Helix: The Iconic Structure of DNA

The paragraph describes the groundbreaking discovery of the DNA double helix by Watson and Crick. It explains the structure of DNA, highlighting its backbone made of sugar and phosphate, and the four nitrogenous bases—adenine (A), thymine (T), cytosine (C), and guanine (G)—that pair up within the helix. The significance of this pairing is that it provides a mechanism for DNA replication, ensuring the transmission of genetic information. The narrative also connects this discovery to Charles Darwin's theory of evolution, suggesting that all life on Earth may have evolved from a single common ancestor, an idea that was supported by the cell theory and the understanding of DNA.

20:09

🌿 Darwin's Evolutionary Theory and the Primordial Life Form

This section explores Darwin's thoughts on the origins of life, as expressed in a private letter to Joseph Hooker. Darwin speculated that life may have begun in a 'warm little pond' with various chemical substances, leading to the formation of a protein compound that could undergo further complex changes. The narrative suggests that Darwin's hypothesis represented a shift away from the idea of a creator and towards a chemical origin of life. It also discusses the connection between Darwin's theory of evolution and cell theory, proposing that all life on Earth descended from a single cell, an idea that was revolutionary for its time.

25:12

🚀 Astrobiology and the Extraterrestrial Origins of DNA

The final paragraph discusses the field of astrobiology and the search for evidence of life beyond Earth. It features Dr. Zita Martins, who analyzes ancient meteorites for organic molecules that could provide clues to the origins of life. The narrative describes the discovery of extraterrestrial organic molecules within a meteorite from Murchison, which is nearly as old as the solar system. These molecules, including a component of our genetic code, suggest that the building blocks of life may have an extraterrestrial origin, challenging our understanding of life's inception and supporting the idea that life's chemistry is not confined to Earth.

Keywords

💡Theodore Schwann

Theodore Schwann was a 19th-century German physiologist known for his significant contributions to the field of cell theory. He is a central figure in the video as he is credited with discovering the ubiquity of cells in all living organisms. His work in Berlin during a time when it was a hub for anatomical studies led to the groundbreaking understanding that both animal and plant life are composed of cells, thus unifying the previously separate fields of botany and zoology.

💡Cell Theory

Cell Theory is a fundamental concept in biology that posits all living organisms are composed of cells, the cell is the basic unit of life, and new cells arise only from pre-existing cells. The video discusses how Schwann's work helped to establish cell theory, showing that cells are the common structural and functional units in all living things, which was a revolutionary idea at the time.

💡Microscope

The microscope is an essential scientific instrument used to observe objects that are too small to be seen by the naked eye. In the context of the video, Schwann's use of a Lister-style microscope and innovative staining techniques allowed him to observe cells in animal tissue. Additionally, the video mentions the van Leeuwenhoek microscope, which was a simple yet powerful tool that enabled the discovery of microorganisms in water, illustrating the critical role of microscopy in advancing biological understanding.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. The video discusses the discovery of DNA's structure and its significance in understanding heredity and evolution. The term 'nuclein', coined by the scientist Misha, later became known as DNA, and the video describes how DNA was first isolated from the nuclei of cells.

💡Double Helix

The double helix is the structure of the DNA molecule, consisting of two chains that spiral around each other. The video highlights the work of Watson and Crick, who proposed the double helix model of DNA, which explained how genetic information could be stored and replicated. This model is now iconic in biology and represents a major breakthrough in understanding the molecular basis of life.

💡X-ray Crystallography

X-ray crystallography is a technique used to determine the atomic and molecular structure of a crystal by analyzing the pattern produced when X-rays are diffracted by the crystal's lattice. In the video, Rosalind Franklin's expertise in X-ray imaging was pivotal in capturing the clearest images of DNA, which ultimately led to the discovery of its double helix structure.

💡Evolution

Evolution is the process by which species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce. The video connects the theory of evolution with cell theory, suggesting that all life on Earth evolved from a single common ancestor, a concept introduced by Charles Darwin in 'On the Origin of Species'.

💡Astrobiology

Astrobiology is an interdisciplinary scientific field that examines the origins, evolution, distribution, and future of life in the universe. The video discusses how astrobiologists, like Dr. Zita Martins, study extraterrestrial organic molecules found in meteorites, which may have contributed to the origins of life on Earth, thus linking the fields of biology and astronomy.

💡Meteorite

A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the Earth's atmosphere. The video describes how meteorites, particularly the Murchison meteorite, contain organic molecules that are fundamental to life, suggesting that the building blocks of life may have an extraterrestrial origin.

💡Genetic Code

The genetic code is the set of rules by which information encoded in genetic material (DNA) is translated into proteins by living cells. The video mentions the discovery of components of the genetic code within a meteorite, indicating that the fundamental molecules necessary for life may have originated outside of Earth, challenging our understanding of life's origins.

Highlights

Theodor Schwann's innovative work in Berlin led to the unification of animal and vegetable biology through the discovery of cells.

Berlin was the European Center for Anatomy, attracting brilliant biologists like Schwann to its prestigious institutions.

Schwann's use of innovative staining techniques and advanced microscopes revealed the cellular structure in various samples.

The field of anatomy was in disarray, with a lack of understanding of the basic structures that make up living organisms.

Van Leeuwenhoek's simple yet powerful microscope revolutionized the way we observe the world, magnifying objects up to 500 times.

Van Leeuwenhoek's curiosity led him to examine water, discovering the presence of microorganisms, a fundamental breakthrough in science.

Flemming's study of white blood cells and the nucleus revealed the molecule DNA, a significant step in understanding cellular composition.

Flemming's resourcefulness in obtaining white blood cells from infected soldiers and using pepsin from a pig's stomach for his experiments.

Rosalind Franklin's expertise in X-ray imaging contributed to capturing the first clear images of DNA's structure.

Watson and Crick's discovery of the DNA double helix and the specific base pairing of A-T and C-G, a landmark moment in biology.

Darwin's theory of evolution by natural selection and its implication that all life on Earth descended from a single common ancestor.

The integration of cell theory and evolution suggests that all life began with a single cell, a profound concept in biology.

Darwin's later hypothesis that life on Earth may have begun with a chemical process in a 'warm little pond'.

Astrobiology's discovery of extraterrestrial organic molecules in meteorites, hinting at the possibility of life's building blocks originating from space.

Doctor Zita Martins' research indicating that components of our genetic code may have been extraterrestrial and present in ancient meteorites.

The Murchison meteorite, dated nearly as old as our solar system, contained molecules that are fundamental to our genetic code.

Transcripts

The stage was set, but what was still lacking with a scientist, with the imagination

to see cells for what they really were.

And here in Berlin, one young and ambitious man

was about to break the impasse.

Theodore Schwann The two strands of biology, animal

and vegetable were about to come together.

At the time, Berlin was the European Center for Anatomy

and the university, the magnet for the most brilliant

biologists around.

Theodore Schwann was keen to make a name for himself

and took a position at the prestigious Anatomical Museum.

Be warned, though,

it's not for the faint hearted.

A guidebook comments.

Boys will be admitted only in the company of their fathers or teachers,

and of the female sex only midwives will be granted admission.

The visitors attention is called mainly to the wealth of nerve preparations,

a long array of monstrous births and about 500 animal skeletons.

The field of anatomy was in chaos.

Nobody really knew what animals or humans were made of.

Researchers believed that they were built of many different structures

granules, fibers, tubes, globules and bladders,

and none of them seemed any more important

than the others.

Animal studies were seriously lagging behind botany,

and this was because the cells are so much harder to see.

So the scientists didn't really realize there were any cells there at all.

And this was fueling the notion that somehow animal tissue

was fundamentally different from that of plants.

But Schwann

used innovative ways to stain his animal tissue

and he had one of the new Lister style microscopes.

He kept finding the same type

of globular structure in all the different samples.

We know that Schwann was looking at cells.

But at the time, researchers used different terms to describe

what they were seeing.

Caution Google Chan and Selam.

The penny hadn't dropped, but they were looking at the same thing.

And without this connection,

they couldn't make the intellectual leap that cells were common to all lifeforms.

This is a replica of van Leeuwenhoek microscope.

Look how simple it is.

It's just a piece of brass, and it's got one tiny hole

with the lens in it, which is maybe a millimeter across.

Yet this is the gadget that transformed

the way we see the world.

A tiny lens yet

more powerful than any other.

Van Leeuwenhoek knew that it's

the curvature of a lens that bends the light passing through it.

So making the object being observed here is a fully a pair larger.

And because Van Leeuwenhoek was a master craftsman,

he could curve the lens more than anybody else.

Almost to the point, it was spherical.

This allowed him to magnify objects

up to 500 times.

No one would make

a more powerful microscope for over a century.

So he now had the technology.

But what did he look at?

He went from linen to fleas to the sting of a bumblebee

and pretty much anything he could get his hands on.

And one of the things he looked at was water.

He noticed in a lake near Delft

the water change color with the seasons, and he figured there might be something

in the water that he could discover.

Many of the fundamental breakthroughs

of science seem so simple, so absurdly simple.

But we shouldn't forget that until Van Leeuwenhoek

no one had the curiosity to find out what might be lurking

in the water.

He raced home to take a closer

look with his microscope.

The man who's going to help me study the water is Hans Loncar.

He keeps the spirit of Van Leeuwenhoek alive

by making replicas of his microscopes

to grind a lens.

Hans needs no special glass, just a shard from an old jam jar.

Will do.

The only way to get enough curvature in a lens

is to make it tiny.

This was Van Leeuwenhoek secret,

and it requires great skill and patience.

Van Leeuwenhoek built a staggering 247 microscopes, a new one

every couple of months for over 50 years,

and told nobody how he made them.

We've placed a drop of my lake water

onto a slide that slots into the device.

With a bit of luck, I'll be able to see what van

Lay will look so

now I've looked down a fair few microscopes in my time.

And this is nothing like anything I've used before.

It's fiendishly difficult to use.

I've got hands with me just in case I can't see a thing.

So what do I actually do?

Where am I looking at? Alongside.

You must look through this hole. Yep.

A very tiny hole.

And there's a lens in it. Yes.

And the lens, The sort of, as you see, the sample.

The sample that is put between the glass.

So if I hold it up to the light like this, close to your eyes.

And I can see.

I can see green.

There is a focus.

You know there's a focus. Yes, there is a focus.

You know, this might be me so I can move it actually away.

Away from my eye.

This one. This is me trying to help.

It's so simple, and it works so well.

Yeah, that works.

It really works.

It's now in focus.

wow.

my God.

You can actually see moving

creatures. Yes.

that's incredible.

Misha’s job here at the castle was to study the chemistry of white blood cells.

He decided to look at the large nucleus at the center of the cell

and find out what it was made of.

To do this, he needed two things a ready supply of cells

and a way of getting rid of the gloop so he could study the bare

nucleus.

Getting

hold of white blood cells would normally have been tricky,

but Tübingen was the ideal place.

The region had been at war with Prussia.

Hundreds of injured soldiers with infected wounds lay in the barracks

next to the hospital.

Their wounds were oozing copious amounts of pus,

which is full of white blood cells so revolting as it sounds,

Misha collected their old bandages so he could scrape off the pus.

Meesha needed something else.

His next stop was the local slaughterhouse to collect a pig's stomach.

I look here it is all disgusting.

He was interested in the mucus that lines the stomach.

This contains an enzyme called pepsin,

which helps break down and digest food.

Where's the pepsin? Look here. This.

This is the pepsin.

This sort of gloopy stuff.

Yeah, there's not much of it.

No, that's all.

And this is what digests.

Helps digest the food in the stomach. Yeah.

Smells like a pig's stomach to me.

With the pepsin maker now had all he needed for his experiment.

And this is a delicacy in Tubingen. Yes.

You can fill it with bread or you can cut it in stripes

and then you cook it and eat it with bread.

Is it tasty? Yes.

I'm not sure about that.

Misha carried the bandages

and the pig's stomach back to the lab.

If he was right,

the pepsin would break down the white blood cells.

Then, for the very first time, it would be possible to examine

the dense nucleus at the heart of the cell.

Nowadays, we do analysis like this using precision equipment.

But of course, Misha didn't have any kit like that, so it wasn't easy.

First he had to scrape the pus from the bandages.

Now this is mayonnaise.

But you get the idea.

Then he had to wash the pepsin out of the pig's stomach

using an acid and mixed it with the pus.

After the enzyme had done its work and digested the cells,

only then could he analyze the nucleus on its own.

Now the big question was

what did the nucleus consist of?

Misha spent months analyzing its chemistry

and he found it contained a rather strange

molecule.

This molecule was made up of carbon, hydrogen,

oxygen and nitrogen.

He knew these elements were

found in all living things,

but this molecule contained

something extra phosphorus,

and that made it different,

very different.

It was an entirely new kind of molecule because he found it in the nucleus.

Misha called it nuclei, and we now know it

as DNA.

Intrigued,

Misha repeated his experiments on sperm cells from frogs,

carp, bulls and salmon.

Every time he found exactly

the same molecule.

Incredibly,

some of it has survived here in this test tube.

He's some of the first DNA ever isolated.

It's DNA from salmon sperm that Misha extracted in the 1870s.

Now, it may not look like much, but this brown

powder marks the beginning of a scientific revolution.

The X-rays taken here at King's College were pivotal.

Producing them would be a painstaking job by a brilliant young scientist

working with Wilkins and her name was Rosalind Franklin.

Franklin was an expert in X-ray imaging

with her expertise.

The college hoped to be the first to find the structure of DNA.

She worked in a new laboratory built in the basement

on the rubble of the old college, which had been bombed

here in the lab.

She took strands of DNA and mounted them inside this specially built camera.

The camera chamber was filled with hydrogen to get the very best image

when the X-rays were switched on.

They shone through the DNA and scattered in different directions, creating an image

on a photographic film.

Franklin took over 100 pictures.

Each one could take up to 90 hours of exposure at close range.

Once the

photo was processed, she projected it onto the wall

so she could calculate the exact distance between atoms.

It was picture 51 that showed the best image

of a mysterious DNA molecule.

This distinctive

x shape was the key that would reveal how DNA is built.

But it was not Franklin's name that came to be associated

with the discovery of DNA structure.

Wilkins

was in close touch with scientists from Cambridge who were anxious

to find the structure of DNA before American rivals.

Unknown to Franklin

Wilkins, gave Photo 51 to James Watson, an ambitious young scientist

at Cambridge's Cavendish laboratory, having studied the photo.

Watson and his collaborator, Francis Crick, had a sudden revelation

It would transform them into scientific celebrities

and put the cell at the center of world attention.

This is the Eagle Pub here in Cambridge.

According to Watson, on February the 28th, 1953,

Francis Crick strolled into this pub and announced to fellow

drinkers, We have found the secret of life.

Now, if you ask me, this story is a little bit apocryphal,

probably embellished with some dramatic license.

Nevertheless, the sentiment is bang on and shouldn't be understated.

This marks one of the truly great moments in the history

of science.

Crick and Watson

had worked out the structure of DNA, and very soon

their double helix model was announced to the world.

The structure of DNA is now

the most famous image in all biology.

What Crick and Watson showed is that it's made of two long strands

intertwined into two spirals with sugar and phosphate making up the backbone.

But it's on the inside of the spiral where things get really interesting.

On the inside are four molecules

adenine, thymine, cytosine, and guanine.

They're better known by their letters A, T, C, and G.

They're called bases.

What Crick and

Watson discovered is that these four basic units pair up

millions of times within the double helix, and they pair up in a very specific way.

They always pairs with T

and C, always pairs with G, A and T and C and G,

making up the rungs of the ladder within the double helix.

What Crick and Watson realized is if you split the two strands of the DNA apart,

you have all the information to make two new fresh pieces of DNA.

Every time you have an A, it pairs up with a T,

Every time you have a C, it pairs up with a G.

So when you split them apart, you can replace the missing strand

and make up a new double helix twice.

Genius.

This is the Origin of Species.

The book in which Charles

Darwin outlines the theory of evolution by natural selection.

But this copy is unique and totally priceless.

This is the first copy of the first edition,

the one that the publisher sent to Darwin himself.

Hot off the press.

Now on page 484.

It's a remarkable passage which gives an insight into what

Darwin himself thought about the origins of life.

All the organic beings which have ever lived on this earth have

descended from some one primordial form

into which life was first breathed.

Now, this doesn't simply say that we humans have evolved

from an ape like ancestor.

Now it goes much further than that.

It's suggested that all living things, from insects to elephants, from a hyacinth

to a human, have evolved from one single common ancestor.

And it flew in the face of the Bible's account of creation.

At the time,

Darwin didn't propose a scientific explanation

for what created this original life form.

His notion

that life was breathed into the primordial common ancestor

left room for the creator.

Yet Darwin's

Origin of Species introduced one of the most important thoughts

in science that all life on Earth sprung

from one single organism.

But to know what that organism would have been,

you have to turn to the other big idea around.

In Darwin's day.

It was the theory that cells

form the basis of all living things.

When it was first proposed in the 1830s,

this was a shocking revelation.

From man to flowers to frogs.

It showed.

We're all made up of the same building blocks.

By the time Darwin published his work on evolution,

cell theory was the new bedrock of biology.

And, crucially, scientists had shown

that new cells are born only when existing cells divide.

All living cells are

descended from other cells.

So in just two decades in the 19th century, scientists have come up

with the two biggest ideas in biology cell theory and evolution.

And if you put the two together, there can only be one conclusion

that all life on earth began with one single

cell.

Darwin himself

never connected the two theories in such a direct way.

But what he did do, just 11 years after publishing The Origin of Species,

was make an unholy attempt to explain

how life may have begun.

He expressed this thought in a private letter to his botanist friend

Joseph Hooker,

and this time there was no mention of the creator.

And this is it.

It's incredible.

I've studied Darwin for many years, but this is the first time

I've ever seen one of his letters penned by his own hand.

And I've got to tell you that his handwriting is appalling.

But just listen to what he says.

If we could conceive of some warm little pond with all sorts of ammonia

and phosphoric salts, light, heat, electricity, etc.

present, that a protein compound was chemically formed,

ready to undergo still more complex changes.

So Darwin had done a complete U-turn.

No sign of the creator.

He was now suggesting that life on Earth began with chemistry.

No wonder he stopped going to church.

So how did something as complex as

DNA come into existence in the first place?

Well, to answer that, some people turned to God believing

that DNA is so exquisite it shows the hand

of some kind of intelligent design.

Others turned to the stars.

And here at Imperial College in London,

a surprising discovery has provided a clue

to the origins of DNA.

At the end of this corridor,

pioneers in a field called astrobiology have spent years analyzing rocks

older and planet Earth itself.

These are meteorites,

some of which are more than 4.6 billion

years old.

One of the lead

astrobiologists is Doctor Zita martins.

She looks for evidence of life beyond the confines of Earth

by searching for particular molecules buried inside rocks from outer space.

Are easy to answer.

So what is it about meteorites

that is interesting, that can tell us about the origin of life?

We know that a specific, samples of meteorites,

like the ones I have here,

there past 4.6 billion years old.

They're, as old as the formation of our early solar system.

This is 4.6 billion years old. Yes.

It's just it's amazing how exciting to hold these samples in your hands.

And that hasn't changed in close to 5 billion years.

Know when you first start looking at this, it looks like a rock, but

you are finding stuff in here.

Yes. We're finding organic molecules.

Extraterrestrial organic molecules

that may have been important for the origin of life in our planet.

And that's why it's so exciting.

So what you're saying is that up in space, which we think of as a big vacuum,

actually, there's masses of chemistry just going on

which is actually creating these, the building blocks for ourselves.

Exactly.

We think the spaces an empty place, but it's not.

It's bubbling with the chemical reactions with activity.

Exactly.

In 2003, Zita got hold of one particular sample

whose molecules would reveal something spectacular.

It was from a meteorite that had fallen to Earth

in 1969, near the Australian town of Murchison.

It was dated to be nearly as old as our solar system.

Thanks to new technology,

Zita is now able to analyze the molecules inside the rock.

And she's going to show me why this particular meteorite

has made such an impact.

Now, this is precious stuff. It is precious.

So usually we only have access to milligrams of meteorites.

So you have to be really careful and not mess up what you're doing.

Yeah, I can feel a sneeze coming on. You might want to run away.

I'm going to run away.

It's essential that I don't accidentally ruin the evidence.

So the

meteorite is sealed inside a glass tube to prevent contamination

from DNA and other molecules on Earth.

Once dissolved in solution, the sample can then be analyzed by a machine

capable of detecting the molecules that make up the genetic code.

Okay, Zita, you've analyzed

the meteorite sample using this pretty awesome machine.

Show me what you find.

So what you find is something like this.

This represents one of the basis of our genetic code.

So this is a sort of signature

for one of the letters that makes up the genetic code for all life.

Exactly.

And this comes out of a 4.5 billion year old meteorite.

This is present in the Murchison meteorite.

It must have been mindblowing to see that for the first time.

It was a very exciting and amazing moment, actually.

I mean, conceptually, that's just out of this

world, literally out of this world.

Because what you're talking about is something which is absolutely inherent

to life, to every single cell on Earth.

And it existed before the Earth even existed.

And we finally have proven that, components of our genetic code

were in fact extraterrestrial and were present in a meteorite sample.