Hey everyone, Joe here. While some might argue that the most significant year in the history of soup was 1962, when Andy Warhol released his iconic pop art featuring soup, I believe the most important year for soup was actually a decade earlier, in 1952. This was when a scientist named Stanley Miller created what we call primordial soup.
Miller’s experiment was revolutionary. He took simple chemicals, similar to those found on early Earth, and bubbled them through a tube while applying electricity. After a few days, he discovered amino acids in the mixture. Amino acids are the building blocks of proteins, which are essential for life. The idea that life could originate from a mixture of chemicals isn’t new. In the 1920s, two scientists theorized about life arising from a “prebiotic soup,” and even Charles Darwin speculated about life forming in “some warm little pond” back in 1871.
What made Miller’s experiment so groundbreaking was that it provided evidence that non-living materials could transform into living organisms. However, the complexity of even the simplest bacteria today makes it hard to believe they simply emerged from a primordial soup. The truth is, they didn’t.
To understand the origin of life, we need to ask not how life started, but when. Life on Earth couldn’t exist before the planet itself, which formed around four and a half billion years ago during the Hadean Era. Shortly after, a collision with another planet melted Earth’s crust and formed the moon. Once the crust cooled, liquid water appeared briefly. However, for the next few hundred million years, Earth was bombarded by massive space rocks, boiling away oceans and melting the crust again. Life couldn’t exist until things stabilized about four billion years ago, marking the beginning of the Archean Eon.
This period represents the earliest possible time life could have started on Earth, known as the habitability boundary. Fossil and chemical evidence suggests that early microbes existed by 3.7 billion years ago, which we refer to as the biosignature boundary. At some point during this time, non-life transitioned into life, a process we call abiogenesis.
While we don’t have a time machine to pinpoint the exact moment life began, we can ask ourselves: what is life? Surprisingly, biology doesn’t have a clear definition. In his 1949 book “What Is Life?”, biologist J.B.S. Haldane stated, “I am not going to answer this question.”
Life can be defined in many ways, but these definitions often fall short. Perhaps we’re asking the wrong question; life isn’t merely a thing that exists, but rather what living things do. In school, many learn a checklist of characteristics that define life, often summarized as MRS GREN. However, this list is based on our current understanding of life, which was likely much simpler in its early stages.
Physicist Erwin Schrödinger observed that while living cells exhibit a high degree of order and complexity, they also resist decay, which he described as a struggle against entropy. Since then, we’ve learned more about entropy, and it seems that the rise of complexity is as inevitable as its decay. Living organisms create closed systems to maintain order, but this definition overlooks a crucial aspect: living things evolve.
The earliest life forms must have contained molecules—chains of atoms—that carried information, providing instructions for building and functioning. These molecules would have replicated and diversified, with some variations being more effective at survival, leading to evolution by natural selection. Thus, life is a product of evolution.
With this understanding, we can propose a better definition: life began when molecules of information started to reproduce and evolve through natural selection. Now that we have a definition, we can outline some criteria for what it means to be “alive”:
While these rules are helpful, the ultimate question is how did this happen? Let’s examine each requirement and assess their likelihood based on scientific knowledge.
Today, most cellular machinery is made of proteins—chains of folded amino acids. In modern cells, proteins are produced by copying genes from DNA into RNA, which serves as a blueprint. This process is known as the central dogma of biology. However, there’s a paradox here: DNA requires proteins to replicate, and cells need DNA to produce proteins. So, which came first?
We can resolve this paradox by proposing that in the earliest days of life, there was no DNA or protein; instead, RNA performed both functions. RNA is similar to DNA but has a different structure and can fold into various shapes to perform tasks. RNA enzymes, known as ribozymes, can facilitate essential chemical reactions, suggesting that life may have originated in an RNA world.
Although the RNA-only world no longer exists, scientists have created ribozymes capable of self-replication, allowing RNA to evolve. Evidence of this RNA-centric life can be found in our cells today, particularly in the ribosome, which is primarily composed of RNA.
To explore the origins of life further, we must consider where life began. Theories suggest that life either originated on Earth or was brought here from elsewhere. It’s known that space contains the chemical building blocks of life, found in meteorites. However, the idea that life was delivered to Earth via space rocks, known as panspermia, lacks proof and doesn’t explain how life originated; it merely shifts the question.
Life likely began on Earth. While early Earth had the necessary chemical ingredients, the primordial soup concept falls short because those chemicals require an energy source to react. We can gain insight into this primordial energy by examining our cells. Instead of relying on lightning or heat, cells generate energy by creating a gradient of hydrogen ions, which powers cellular machinery.
The earliest life forms would have needed a natural energy source, likely found at deep-sea hydrothermal vents. These vents could have provided the conditions for the first cells to form, as molecules with hydrophobic and hydrophilic properties naturally create bubbles and sheets, forming cell membranes. The hydrogen ions flowing near these pockets in the rock could have powered early life forms, allowing them to resist entropy.
For these primitive life forms to evolve into more complex organisms, they needed to transition from RNA to DNA for genetic information storage and from ribozymes to proteins for cellular machinery. This shift opened up new possibilities for energy storage and utilization, enabling early life to become more complex and free-living.
The last universal common ancestor (LUCA) represents the culmination of this journey into the origin of life on Earth. Much has transpired since then. Our understanding is based on observable evidence rather than mere speculation. We’ve established when life could have started, defined what life is, and identified clues within our cells that explain how the first life forms met these criteria and where they might have originated.
The only question left unanswered is why, but that’s not a question for science. There are still many gaps in this story, and if you’re seeking a neat answer to how life began, you may be disappointed. Life is simply a phenomenon that occurs, and it continues to evolve as long as conditions allow.
Darwin may not have realized it when he pondered that warm little pond filled with chemicals, but his theory of adaptation and change is powerful enough to encompass life in all its forms, including its earliest iterations. Stay curious!
That was a lot of information! This is probably the most in-depth story I’ve shared on this channel, and it involves some of the science I used to study, making it a lot of fun for me. I hope you enjoyed it as well.
But this is just part of the story of how life began. What happened before Earth became a suitable environment for life? And what occurred after chemistry transitioned into biology? For those answers, check out these videos from our friends at PBS Space Time and Eons.
Recreate a simplified version of Stanley Miller’s experiment in the classroom. Use safe chemicals to simulate the early Earth’s atmosphere and apply a small electric spark to mimic lightning. Observe any changes over a few days and discuss the significance of amino acids in the origin of life.
Engage in a class debate about what constitutes life. Use the criteria outlined in the article and explore different perspectives. Consider how these definitions apply to potential life forms on other planets or moons.
Conduct a research project on hydrothermal vents and their role in the origin of life. Present your findings on how these environments could have provided the necessary conditions for early life to thrive.
Use a computer simulation to explore the concept of an RNA world. Experiment with how RNA molecules could replicate and evolve over time, leading to the development of more complex life forms.
Investigate the theory of panspermia and its implications for the origin of life on Earth. Create a presentation or video discussing whether life could have been transported to Earth from elsewhere in the universe.
Here’s a sanitized version of the provided YouTube transcript:
—
Hey everyone, Joe here. Some might argue that the most significant year in the history of soup was 1962, when Andy Warhol released his iconic pop art featuring soup. However, I believe soup’s most important year was actually a decade earlier, in 1952, when a scientist named Stanley Miller first created primordial soup.
Miller’s experiment involved taking simple chemicals, similar to those found on early Earth, bubbling them through a tube, and applying electricity. After a few days, he discovered amino acids floating in this mixture—these are the building blocks of proteins and essential ingredients for life. The idea that life’s origins could stem from a mixture of chemicals is not new; in the 1920s, two scientists theorized about life arising from what they called a “prebiotic soup.” This speculation even dates back to Charles Darwin, who in 1871 wondered if life might have formed in “some warm little pond.”
What made Miller’s experiment groundbreaking was that it provided evidence that non-living materials could easily transform into living organisms. However, everything we see today, even the simplest bacteria, is incredibly complex, making it hard to believe they simply emerged from a primordial soup. The truth is, they didn’t.
We’re going to explore the origin of life, and along the way, we’ll encounter various questions and challenges, and we’ll need some assistance from our friends. We’ll discover that Miller’s primordial soup isn’t exactly how this story began.
The first question we should consider isn’t how life started, but when. Life on Earth couldn’t exist before the planet itself, and it began around four and a half billion years ago, during the Hadean Era. Shortly after, another planet collided with the young Earth, melting the crust and forming the moon. Once the crust cooled, there was some liquid water for a time. However, for the next couple of hundred million years, Earth was bombarded by massive space rocks, causing the oceans to boil away and the crust to melt again, making it inhospitable for life until things stabilized about four billion years ago, marking the beginning of the Archean Eon.
This period represents the earliest possible time life could have started on Earth, known as the habitability boundary. Fossil and chemical evidence suggests that early microbes existed by 3.7 billion years ago, which we refer to as the biosignature boundary. At some point during this time, non-life transitioned into life, a process we call abiogenesis.
While we don’t have a time machine to pinpoint that exact moment, we can ask ourselves: what is life? You might think biology would have a clear definition for life, but as a biologist, I can tell you it’s more complicated than it seems. In his 1949 book “What Is Life?”, biologist J.B.S. Haldane stated, “I am not going to answer this question.”
Life can be defined in many ways, but these definitions often fall short. Perhaps we’re asking the wrong question; life isn’t merely a thing that exists, but rather what living things do. In school, many learn a checklist of characteristics that define life, often summarized as MRS GREN. However, this list is based on our current understanding of life, which was likely much simpler in its early stages.
Physicist Erwin Schrödinger observed that while living cells exhibit a high degree of order and complexity, they also resist decay, which he described as a struggle against entropy. Since then, we’ve learned more about entropy, and it seems that the rise of complexity is as inevitable as its decay. Living organisms create closed systems to maintain order, but this definition overlooks a crucial aspect: living things evolve.
The earliest life forms must have contained molecules—chains of atoms—that carried information, providing instructions for building and functioning. These molecules would have replicated and diversified, with some variations being more effective at survival, leading to evolution by natural selection. Thus, life is a product of evolution.
With this understanding, we can propose a better definition: life began when molecules of information started to reproduce and evolve through natural selection. Now that we have a definition, we can outline some criteria for what it means to be “alive”:
1. A living thing must work to avoid decay and disorder.
2. To do this, a living thing must create a closed system or be composed of cells.
3. It must have a molecule that carries information about building cellular machinery.
4. This information must evolve through natural selection.
While these rules are helpful, the ultimate question is how did this happen? Let’s examine each requirement and assess their likelihood based on scientific knowledge.
Today, most cellular machinery is made of proteins—chains of folded amino acids. In modern cells, proteins are produced by copying genes from DNA into RNA, which serves as a blueprint. This process is known as the central dogma of biology. However, there’s a paradox here: DNA requires proteins to replicate, and cells need DNA to produce proteins. So, which came first?
We can resolve this paradox by proposing that in the earliest days of life, there was no DNA or protein; instead, RNA performed both functions. RNA is similar to DNA but has a different structure and can fold into various shapes to perform tasks. RNA enzymes, known as ribozymes, can facilitate essential chemical reactions, suggesting that life may have originated in an RNA world.
Although the RNA-only world no longer exists, scientists have created ribozymes capable of self-replication, allowing RNA to evolve. Evidence of this RNA-centric life can be found in our cells today, particularly in the ribosome, which is primarily composed of RNA.
To explore the origins of life further, we must consider where life began. Theories suggest that life either originated on Earth or was brought here from elsewhere. It’s known that space contains the chemical building blocks of life, found in meteorites. However, the idea that life was delivered to Earth via space rocks, known as panspermia, lacks proof and doesn’t explain how life originated; it merely shifts the question.
Life likely began on Earth. While early Earth had the necessary chemical ingredients, the primordial soup concept falls short because those chemicals require an energy source to react. We can gain insight into this primordial energy by examining our cells. Instead of relying on lightning or heat, cells generate energy by creating a gradient of hydrogen ions, which powers cellular machinery.
The earliest life forms would have needed a natural energy source, likely found at deep-sea hydrothermal vents. These vents could have provided the conditions for the first cells to form, as molecules with hydrophobic and hydrophilic properties naturally create bubbles and sheets, forming cell membranes. The hydrogen ions flowing near these pockets in the rock could have powered early life forms, allowing them to resist entropy.
For these primitive life forms to evolve into more complex organisms, they needed to transition from RNA to DNA for genetic information storage and from ribozymes to proteins for cellular machinery. This shift opened up new possibilities for energy storage and utilization, enabling early life to become more complex and free-living.
The last universal common ancestor (LUCA) represents the culmination of this journey into the origin of life on Earth. Much has transpired since then. Our understanding is based on observable evidence rather than mere speculation. We’ve established when life could have started, defined what life is, and identified clues within our cells that explain how the first life forms met these criteria and where they might have originated.
The only question left unanswered is why, but that’s not a question for science. There are still many gaps in this story, and if you’re seeking a neat answer to how life began, you may be disappointed. Life is simply a phenomenon that occurs, and it continues to evolve as long as conditions allow.
Darwin may not have realized it when he pondered that warm little pond filled with chemicals, but his theory of adaptation and change is powerful enough to encompass life in all its forms, including its earliest iterations. Stay curious!
That was a lot of information! This is probably the most in-depth story I’ve shared on this channel, and it involves some of the science I used to study, making it a lot of fun for me. I hope you enjoyed it as well.
But this is just part of the story of how life began. What happened before Earth became a suitable environment for life? And what occurred after chemistry transitioned into biology? For those answers, check out these videos from our friends at PBS Space Time and Eons.
—
This version maintains the essence of the original transcript while removing any informal language and ensuring clarity.
Life – The condition that distinguishes living organisms from inanimate matter, characterized by growth, reproduction, and the ability to respond to stimuli. – Scientists study the various forms of life to understand the complex interactions within ecosystems.
Origin – The point or place where something begins, arises, or is derived. – The origin of species is a fundamental concept in evolutionary biology, explaining how diverse life forms have evolved over time.
Amino – Relating to or containing an amine group, which is a functional group consisting of a nitrogen atom attached to hydrogen atoms, alkyl groups, aryl groups, or a combination of these. – Amino acids are the building blocks of proteins, playing a crucial role in cellular function and structure.
Acids – Substances that release hydrogen ions when dissolved in water, often having a sour taste and capable of turning litmus paper red. – Nucleic acids, such as DNA and RNA, are essential for storing and transmitting genetic information in living organisms.
Evolution – The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth. – Charles Darwin’s theory of evolution by natural selection provides a scientific explanation for the diversity of life on Earth.
RNA – Ribonucleic acid, a nucleic acid present in all living cells, playing a role in coding, decoding, regulation, and expression of genes. – Messenger RNA (mRNA) carries genetic information from DNA to the ribosome, where proteins are synthesized.
DNA – Deoxyribonucleic acid, the molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms. – The double helix structure of DNA was first described by Watson and Crick in 1953.
Cells – The basic structural, functional, and biological units of all living organisms, often referred to as the “building blocks of life.” – The study of cells, known as cell biology, is essential for understanding the complex processes that sustain life.
Entropy – A measure of the disorder or randomness in a system, often associated with the second law of thermodynamics. – In biological systems, entropy tends to increase, leading to the need for energy input to maintain order and sustain life.
Abiogenesis – The original evolution of life or living organisms from inorganic or inanimate substances. – Abiogenesis is a scientific hypothesis that seeks to explain how life on Earth could have arisen from non-living matter.
