How did Life begin on Earth? | Mystery of our Origin | Dhruv Rathee

"The first living thing on Earth," "how did it come alive? " "Was there divine intervention" "that breathed life into it? " "Or was it an alien which came to live on Earth?

" "After observing it for a few weeks," "they discovered something truly surprising. " "This was the birth of single-cellular organisms. " "They later evolved into living beings.

" "Life didn't begin on Earth. " "It began in space. " Hello, friends!

Do you know that your DNA is 60% similar to a banana's DNA? No, I'm not kidding. This is true because humans and bananas have the same ancestor if you go far back in time.

That means, our and a banana's great great great hundred-millionth great-grandparent, is the same. In fact, this is true not only for bananas, but for every animal and plant on this planet. And if you go further back in time, 3.

7 billion years ago, you will find that there was a single common ancestor of all living organisms on Earth. LUCA. The name LUCA stands for Last Universal Common Ancestor.

It was a single-celled organism, a microbe. Scientists believe that it lived in tropical places. And all the living things on planet Earth today, plants, animals, fungi, algae, and even bacteria, all of us evolved from this one organism.

LUCA wasn't the first living organism on Earth. There must have been other living organisms before it. But scientists haven't figured out what they looked like.

In fact, scientists don't know what LUCA looked like. But the important fact is that LUCA was a living organism. Because this raises the question how did LUCA come to life?

How did the first living thing on earth become a living thing? Was there a divine force that breathed life into it? Or was it an alien that came to live on earth?

This questions the origin of life. After all, how can non-living matter, stones, soil, water, and some elements turn into living and breathing organisms? Let's understand this mystery in this video.

Friends, this is the fifth video in the Evolution series. I made 4 videos before this as you can see on the screen. The first was on the Theory of Evolution.

In the second we discussed how humans evolved from monkeys. In the third we discussed which came first, chicken or egg. And in the fourth, we talked about how the earth was formed within our solar system.

And now, in the fifth instalment of this series, we will talk about how living beings emerged from non-living things. When you think about it, it sounds nearly unbelievable. How can this be possible?

Up to 200 years ago, most scientists thought so too. Most scientists believed that there is some sort of a "life force" in every living being keeping us all alive. But in the 1780s, a French chemist, Antoine Lavoisier conducted the first experiment which proved that perhaps living things aren't that different from non-living things.

He took a guinea pig and measured its body heat. He observed how fast the ice melted using this animal's body heat. As well as the amount of carbon dioxide it releases.

Then he compared these findings with a piece of coal which released the same amount of carbon dioxide and melted the same amount of ice as the body heat of the animal. After seeing this, he concluded that life is a chemical process. Non-living things and living things both work on the same chemical principles.

A few years later, in the 1790s, an Italian doctor, Luigi Galvani, was working on some dead frogs. He had the frogs' legs hooked on a brass hook and he was holding a steel blade. The blade brushed by the legs by mistake, and the legs started shaking.

When he saw the legs of the dead frogs shaking, he thought that he had discovered the life force. He named it 'animal electricity. ' He said that it is some kind of an electrical force, present in every living thing which cause the movement.

But his conclusion was proven wrong by Alessandro Volta. He said that it wasn't because of the legs, rather, it was due to the two metals. When the steel blade hits the brass hook, electricity is produced, and the reaction is caused by that.

Later, Volta used this principle, to invent the world's first electric battery. These cells that we use today, the ones carrying voltage, 'Voltage' was named after Volta. But still, most people weren't convinced.

They still believed that living beings carry some sort of special energy that's absent in non-living things. Actually, there was a reason why scientists thought so. Most of the chemical compounds found in a living being, like fats, proteins, and sugars, weren't found in any non-living thing.

Like stones, soil, and other minerals. By the way, this is where organic chemistry was born. We've been taught organic chemistry and inorganic chemistry in school.

Have you ever wondered why these two are named like this? Because most of the organic compounds are the ones found in humans and living beings. And the inorganic compounds are mostly found in non-living things.

That's why scientists named these 'Organic Compounds. ' And scientists believed that these organic compounds since they are found only in living things, there must be some sort of a life force creating these organic compounds. The turning point towards the solution to this mystery came in 1828 when German chemist Friedrich Wöhler accidentally created an organic compound from an inorganic compound.

He synthesised urea from ammonium cyanate. The same compound which is found in urine. This experiment shocked everyone.

For the first time, people were surprised to see that inorganic compounds can create something that can be found in human bodies. Since this point, the concept of life force started losing credibility. In the 1850s, a chemist living in Paris, Marcellin Berthelot, began a total synthesis program to put an end to this concept.

He said that using only carbon, hydrogen, oxygen, and nitrogen he could create all organic compounds. And he did. First, he made hydrocarbons, then converted the hydrocarbons into alcohol, then the esters, and later he even made organic acids.

Today, we study these in 11th and 12th grades. By this point, people had begun accepting that organic compounds could be formed using chemical reactions. But organic compounds do not have life in them.

They aren't alive. So what gives life to living beings? For this, it is important to define 'Life.

' What does it mean when we say that something is 'living'? Does living mean being able to move around? If yes, then by this definition, though all animals are living beings, but not the trees and plants that cannot move.

However, they are living beings. If we consider the ability to reproduce as the essence of life, it would include plants, animals, bacteria, and everything. But what about animals like mules which can't reproduce?

They are alive, living things, but the reproduction definition won't fit them. In 2011, biophysicist Edward Trifonov tried to look for the definitions of life. He found 123 different definitions.

There was a common consensus among all these definitions. "Life is self-reproduction with variation. " In this definition, included such creatures that are born out of reproduction even if they cannot reproduce.

But instead of simplifying things, we need to understand the differences if we want to answer this mystery of how non-living things can change into living things. The first difference is Complexity. Living beings are made up of numerous chemical compounds.

Non-living things aren't as complex. The second difference is Metabolism. Every living thing needs food to get energy.

All animals consume food to produce energy. Plants and trees consume sunlight to produce energy. And even microbes like bacteria and viruses consume something or the other from their environment to produce energy.

And whatever remains thereafter is released back into the environment. This is called Metabolism. Metabolism is evident among all living beings present on earth.

The third difference is the Boundary. The living organisms are separated from their surrounding environment through a boundary. Our skin cells create a barrier against the outside environment.

Trees and plants have cells for this too. And in bacteria, viruses, and other single-celled organisms, the cell wall does this. To separate and protect the inner contents from the environment outside.

And the fourth condition is Reproduction. We can simplify it further and call it Replication. Even the smallest single-celled microbes can replicate themselves.

The DNA in them can replicate to create more of them. Now, based on these 4 criteria, let's take them one by one, to understand how such life forms were created to meet these criteria. Because, friends, the truth is, the transition from non-living to living did not happen suddenly.

It was slow and gradual, like a spectrum. That's why it is difficult to pinpoint anything on this spectrum. But, gradually, what happened was non-living things started transforming into living things.

First of all, let's take Complexity. How did things as complex as DNA evolve? In this video I explained how our solar system was merely a cloud of dust and rocks, out of which the Sun formed first, and later the Earth.

After Earth's formation, we talked about how there were frequent showers of comets and meteors on Earth. This era is called the Late Heavy Bombardment era. Some scientists believe that the building blocks of our life came from these comets and meteors.

This theory is called the Panspermia theory. According to this, life did not begin on Earth, it began in space. It sounds a bit weird, but today we have solid evidence that the building blocks of life are present in space.

We know this because of Spectroscopy. I have explained this in detail in this video. The spectrum of light emitted by stars and galaxies millions of miles away, is analysed to figure out its chemical composition.

Using data science, we can figure out in detail which elements are present in those stars and galaxies. A field like data science is being used in almost every industry today. Auto-mobiles, finance, media, healthcare, if you want to upskill yourself in this and want to enter this dynamic field, then the sponsor of this video, Scaler.

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In the 1930s, Spectroscopy was used by scientists to study the clouds of gas and dust in our galaxy. They found complex molecules in them. In the beginning, simple molecules like methylene and cyanide were discovered.

Later, as telescopes became more advanced, radio and infrared telescopes were used, to discover molecules of ammonia, water, and formaldehyde in space. In 1969, in Australia, in the Murchison meteorite, more than 20 amino acids were found. After that, scientists discovered urea, glycine, and ethanol in space.

When ethanol, that is alcohol, was discovered in space, the media ran with the headline 'Space Vodka. ' In 2014, molecules like isopropyl cyanide were also discovered. It is similar to the complexity of the amino acids found on Earth.

Sagittarius B2 cloud, which is 25,000 light years away from Earth, was found to have molecules that showed Chirality. You must have studied the concept of Chirality in school. It's when the molecules have a mirror image and you can see their left-handedness and right-handedness.

Chirality is a basic identity of life on earth. Because Chirality is seen in amino acids, DNA, and RNA. There are about 20 amino acids found in every life form on earth.

They are like the building blocks of life. And all these 20 amino acids are already found in space. Apart from these, two types of nucleic acids, first DNA and second RNA are also considered to be the building blocks of life.

Although we have not discovered DNA or RNA in space, we have discovered their building blocks in space. The core component of DNA and RNA is a sugar called Ribose. 25,000 light years away, in a gas cloud like Sagittarius B2, we found sugar glycolaldehyde which reacts with carbon compounds to form Ribose.

This means that the building blocks of the building blocks like DNA and RNA are already found in space. Regarding this, scientist James Lovelock said that the universe is like a big warehouse. With all the spare parts required for life available in it.

Today, most scientists believe that space is like a chemical factory. This means that Earth wouldn't have needed to synthesise most of the molecules. Our solar system, meteors, and comets must have lent many of these complex molecules.

Now, how did these raw materials form into more complex things on earth? To answer this, we have the Primordial Soup Hypothesis. According to this theory, there must have been a rich mixture of inorganic molecules in a hot pond on Earth.

It must have been struck by electricity, drew heat from volcanoes, and it gave a kick start to Life. "Lightning strikes the chemical soup. " "At the right place and the right time.

" "Billions of bolts of electricity triggered a chain of improbable coincidences to create the first-ever cell. " In 1871, Charles Darwin said that in a small hot pond, that had ammonia, phosphates, electricity, light, and heat some sort of a protein must have been created first. And later, that protein would have evolved into Life.

But is it truly possible? A practical experiment was conducted in 1953 by Stanley Miller and Harold Urey. They took a large 5-litre glass container and filled it with ammonia gas, methane gas, and water vapour.

They introduced sparks of electricity into the container similar to the conditions on Earth 4 billion years ago. After observing it for a few weeks, they noticed something very surprising. These few inorganic compounds were changing into some of the building blocks of life.

A few weeks later, amino acids and carbon compounds were formed in this container. This experiment proved that with the right conditions and raw materials, the building blocks of life will start forming on their own. The second criterion is Replication.

For this, we have the Clay Mineral Hypothesis. Charged surfaces of clay help in binding together the primary organic molecules and in speeding up the reactions between them. Clay provides a surface on which the organic molecules can collect they keep getting concentrated.

Clay was helpful in binding together nucleotide molecules into a chain. Gradually, it is believed that, there was a big enough chain of organic molecules, which is now known as the RNA. RNA could store genetic information and self-replicate itself.

Once again, this has been proven through practical experiments where small particles on clay surfaces mix among each other where clay gives them a platform for molecular assembly. However, it is still a big mystery how did the first RNA molecule form by itself and how did it start to self-replicate. But there have been practical experiments to better understand this and it did clarify some specific things.

For example, in 2009, John Sutherland's experiment. He observed that with simple molecules like hydrogen cyanide, acetylene, and phosphate, under ultraviolet light RNA nucleotides can be formed. Here, we come to the RNA World Hypothesis, according to which RNA evolved first, after that proteins were formed, and then DNA.

Because only RNA has the ability to self-replicate. They multiplied, evolved, and eventually became capable of making strong stable proteins, and these proteins then evolved into DNA. DNA could then store genetic information for a long time in a stable manner, and could make its own copies.

The third criterion is Boundary. Molecules and RNA evolved. but when did they evolve into separate organisms?

When they became distinct from the environment around them. It is not so difficult to imagine this because you can observe a practical example right at your home. Whenever you wash your hands, while you are washing your hand, the soap molecules stick to the dirt and dust on your hands and together they get washed away.

Why does this happen? Because it's the property of fatty acids. As you have studied in school, soap molecules have a hydrophilic part and a hydrophobic part.

A part of the molecule is attracted to water and a part which wants to stay away from water. Because of this, it forms a shape that traps oil, dust, and dirt molecules inside. In a way, it is akin to the formation of a cell-structure.

Where something from the outside cannot enter. These fatty acids turn into Lipids. And in the water, lipids started forming small bubbles.

Chemicals were trapped inside these bubbles. And these lipids evolved into primitive cell membranes. Now, in one of such lipids, RNA molecules were trapped and a boundary was formed trapping the RNA inside the lipids.

The RNA molecules being inside a structure like a cell membrane, what does that remind you of? A cell. That's why they are called Protocells.

Protocells refer to the cells that existed before the cells that we know today. These were the simplest forms of cells and these protocells later evolved into cells when they became more complex. This was the beginning of single cellular organisms.

and they later evolved into living beings. But the fourth criterion remains. Metabolism.

How did metabolism begin? What was the need to consume something? The simple answer is: to get energy.

If RNA and DNA had to replicate themselves, they needed energy. In the beginning, these protocells got this energy from the Earth's environment. At the depths of the ocean, there are often vents on the ocean floor known as Hydrothermal Vents.

Extremely hot water is released from these vents. Scientists believe that life might have begun here. This is known as the Hydrothermal Vent Theory.

According to this theory, life began near these hydrothermal vents and it is believed that LUCA must have been born somewhere around here. To survive, the protocells needed energy so they began trapping the nutrients from this water inside themselves. These nutrients were trapped using fatty acids.

And the nutrients they needed to create amino acids, lipids, RNA, and DNA were used and the leftover nutrients were simply released back into the environment. This became a type of simple metabolism and they got energy from the heat of the water. As life progressed, there was a lot of competition even at the level of single cells.

The hydrothermal vents offered a good environment. The water was rich in nutrients It was mineral-rich water, and it was hot enough to facilitate the reactions. But as soon as a cell moved away from these vents, it didn't have anything.

The only remaining source of energy was to consume other cells. Or to cooperate with them and merge together. We can still see these two traits in animals.

First, Predation. Eating other animals to get energy. And the second is Mutualism.

Co-operating with other living beings and working together. An example of this is a honeybee which takes nectar from flowers and helps pollinate flowers. So, we saw the same thing even at the cellular level, But before that, we need to understand four names.

Prokaryotes, Bacteria, Archaea, and Eukaryotes. Prokaryotes are single-cell organisms. They are of two types.

One is bacteria and the other is archaea. Both are forms of life that originated in different ways. But they originated from the same kind of primordial soup.

That's why they share one-third similarities. The second category is Eukaryotes they are multicellular organisms. Like plants and animals.

2 billion years ago, in the oceans of the Earth, there was a population of Archaea and a population of Bacteria. Both populations lived close to each other. This was a mutually beneficial relationship because bacteria fed on Archaea's waste.

And the closer the bacteria lived, the more benefits did the Archaea get. At one point, bacteria got so close to Archaea that it entered the Archaea's body. The bacteria was tolerated because the Archaea did not see any harm in it.

And when this happened, one cell could maintain its independence inside another cell. This cell is considered to be the ancestor of all multicellular organisms. All complex life on Earth, trees, plants, animals, all of us have evolved from this single-celled organism, which is possible due to the merger of bacteria and archaea.

You'd be wondering how could we figure this out. In the 1960s, an American biologist, Lynn Margulis researched mitochondria that exist in cells. Now, mitochondria's function is to facilitate metabolism.

And to provide energy to the cell. When she studied the DNA, it was found that cells have a different DNA that mitochondria's DNA. Mitochondria's DNA is like the DNA of a bacteria called Typhus which causes fever, headaches, and rash in humans.

So, the conclusion of this study was that mitochondria and the rest of the cell must have been two different organisms at one point in time. And today, there is solid evidence that the merger of archaea and bacteria resulted in the bacteria becoming mitochondria and archaea evolved into the rest of the cells. Mitochondria are found only in eukaryotes, and not in prokaryotes.

So, all multicellular organisms could be born because of this. Without mitochondria, it wasn't possible to have any multicellular organism. All eukaryotes require a lot of energy to survive and this extra energy is provided only by mitochondria.

An average eukaryote can support a genome 200,000 times bigger than a bacterial genome and can command 200,000 times more energy. Due to this large amount of extra energy, eukaryotic cells started developing, genes started developing and the process of natural selection began. So, overall, this transformation from non-living beings to living beings is not something that happened all of a sudden.

A chain of different events had to take place before this, over a long period of time. Specifically speaking, this transformation took at least 2 billion years. It is estimated that the very first life on Earth evolved between 3.

7 billion to 4 billion years ago. And the first multicellular organism is estimated to have evolved at least 1. 5 billion years ago.

It takes so long, and so many different processes have to be executed properly, under the right conditions and with the right raw materials, for this transformation to happen. So it won't be wrong to say that we are all made of stardust. The things that were needed for us to be born, are all present in space.

I hope this video was as informative as always. The link to Scaler is in the description below. And now, if you want to know more about this, about how multicellular organisms evolved to later turn into trees, plants, and humans, I have discussed this in detail in the video on the Theory of Evolution.

You can here to watch it. Thank you very much!