Abstract
Life on Earth didn’t just come about by random chance. Several billion years of chain events, complex chemical reactions, mutations, evolutions and favourable conditions were necessary for the creation of life as diverse and adapted as we can see around us now. Scientists are eager to understand how life came to be, for if they can understand its past, it will help them to comprehend its present, and more accurately predict its future. Because of this, there are countless theories regarding exactly how life came about. This article explores some of the more popular theories of today.
Introduction
Earth Day has been celebrated every year on April 22nd since 1970, and aims to both educate and mobilise people into climate action. Although humans have only roamed the earth for a mere fraction of the Earth’s existence (200,000 years compared to the Earth’s estimated 4.5 billion), our impact on the planet has been both immense and catastrophic. But to really understand and appreciate the true impact of Homo sapiens, it is important to look back on how life on Earth truly began.
Formation of the Planets
The most widely accepted theory for the formation of the Solar System is through accretion theory. This was initially suggested by Otto Schmidt in 1944, and supported by study of moon craters during the Apollo space program in the 1960s. This theory suggests that particles that formed after the Big Bang gradually clumped together, to form small balls, then tiny planets, and gradually build up mass by the collision of these planetesimals with other meteorites that were numerous at the time [1]. The formation of the young Earth is classed as the Hadean Eon due to the hellish, inhospitable conditions on the planet — the constant bombardment of meteorites caused the innards of the planet to melt into magma, giving rise to constant volcanic eruptions, and little to no oxygen in the atmosphere [1]. It was during this eon that oceans arose on Earth, and as the Hadean Eon ended, and the Eoarchean Eon began, the first signs of life began to show.
The Primordial Soup, an RNA world, and quantum superposition
The genesis of life has been estimated to between 3.5 and 4 billion years ago — just after the end of the Hadean Eon [2]. It almost certainly began in the seas, as the land and air would still have been inhospitable to life. Darwin once suggested that life began in some “warm little pond”, and the primordial soup hypothesis suggests that he wasn’t wrong.
The theory was formalised by Alexander Oparin and J. B. S. Haldane, and argues that early atmospheric gases such as water vapour, ammonia, methane and hydrogen combined due to lightning, radiation or heat to form simple organic compounds. These monomers existed in the ocean forming an organic “primordial soup” that led to the formation of larger polymers and, eventually, a molecule with the ability to replicate itself [3]. This hypothesis was supported by the Miller-Urey experiment, where they simulated the primordial atmosphere in a laboratory, and stimulated the mixture with electric sparks. Within a week, the mixture contained amino acids, the building blocks of proteins. Although neither this experiment nor any of its following repetitions has ever yielded a self-replicator, it is still a good indication of the hypothesis’ validity [2][3].
It is now believed that the primitive self-replicator was a form of RNA — called a ribozyme — that could act as both an enzyme and a gene. This means that it could encode its own structure and make copies of itself, without the need for other complex molecules. It would be extremely unlikely for such a complex molecule to form in the primordial ocean by chance, so a current theory as to how this replicator came about is through quantum superposition — a quantum mechanic that allows for the protons and electrons in the molecule to explore a variety of different arrangements at once, until the correct molecular arrangement for a self-replicator is found [3]. Once this first self-replicating molecule was formed, the chain of events leading to the formation of life could begin in earnest. This molecule could reproduce to form more molecules that could mutate to form different substances with different functions, eventually organising itself into the first primitive cell — the Last Universal Common Ancestor, or LUCA, from which all life is derived.
Evolution of Life
Life had begun — but for life to evolve to the vast and diverse proportions that we know now, it was missing one crucial element — oxygen. That’s where cyanobacteria (Prochlorococcus marinus) came in. Cyanobacteria evolved about 2.4 billion years ago and became the world’s first photosynthesizers [4][5]. These bacteria could take in carbon dioxide and water, and, with the help of sunlight’s UV rays, convert it into oxygen and sugars. This was the Great Oxygenation Event, and all forms of complex life owe their existence to this bacteria, that is considered to have produced up to 20% of all global oxygen supplies, and is believed to be the most populous genus on earth, with as many as one hundred octillion of this bacteria alive today [4]. Their limestone-based stromatolite structures can still be seen globally, perhaps most famously dotted along the coastline of Shark Bay in Western Australia.
Increasingly complex cells soon began to develop, with more complex functions, and more complex internal structures to help them complete their tasks. Many of these evolved from a symbiosis of simpler prokaryotic cells in small colonies. Chloroplasts, the photosynthetic organelles found in some eukaryotes, are likely to have evolved from a cyanobacterium or similar photosynthesising bacterium. Mitochondria — organelles that allow for respiration — evolved from endocytosis of purple bacteria that gained energy from atmospheric oxygen. Flagella, cellular ‘tails’ that allow movement, may have evolved from spiral-shaped bacteria (spirochaetes). Life was becoming more complicated, and evolving rapidly [4].
From simple cells evolved more complex, multi-cellular organisms. Some of the earliest self-organising collections of animal cells were sponges and stony corals. While these simple systems prevailed for a long time, they gave way to animals that had more complex systems of organisation, such as bilateral symmetry, movement, and a gut. The oxygen-rich atmosphere allowed organisms to grow to vast proportions. On land, Prototaxites (8 metre high fungi) gave way to Lepidodendron, fifty metre tall early trees that died and fossilised to produce the carbonous coal that humanity has burned so excessively in the last 200 years. Azolla water ferns absorbed so much atmospheric carbon dioxide that they were one of the main reasons as to why the Earth was quickly plunged into an ice age. When they died they sank to the seafloor to form what we now know as crude oil and natural gas. Trilobites moved onto land, to form a diverse array of arthropods, from giant centipedes (Arthropleura) and scorpions (Pulmonoscorpius), to metre-long dragonflies (Meganeura). Early tetrapod fish evolved to leave the oceans and became the first vertebrates to adapt to a new terrestrial niche [4]. The vertebrates that developed a water-tight skin (as opposed to the water-permeable skin of fish and amphibians), became the first fully terrestrial vertebrates – the amniotes. This clade diverged to form two branches — one was early mammals, the other early reptiles, and later, included birds. After the Carboniferous rainforest collapse that occurred 305 million years ago and destroyed much of the Lepidodendron-dominant forests, reptiles could rise to this new niche and become dominant. They had the space to become the prevailing megafauna – dinosaurs.
The age of the dinosaur came, and went with the Cretaceous-Paleogene extinction event. The only remaining group of reptiles was the archosaurs, which included birds and crocodilian reptiles. This group quickly became the dominant carnivores. Mammals continued to exist as small, nocturnal, insectivores. Even after the extinction of the dinosaurs, mammals were still prime prey, and so they remained smaller than a cat for some millions of years. It wasn’t until the Eocene epoch 55 million years ago, when a change in climate allowed for forests to effectively cover the Earth, did mammals finally have the freedom to spread and differentiate into their many forms that we see today. Mammals became more diverse and dominant on Earth. The first primate was Eosimias, from which bigger, more intelligent primates could evolve [6]. About 4.5 million years ago a member of the hominid family (Australopithecus afarensis) began walking on two feet. About 1.8 million years ago, Homo erectus, with its superlative level of brainpower, migrated out of its native Africa to populate Europe and Asia, and evolved techniques of hunting, survival and culture that were far beyond any other mammal at the time. By 25,000 years ago, all other species of human had died out, and one, Homo sapiens, had prevailed [4].
The Anthropocene
Creating even more complex behaviours, such as language, art and religion, Homo sapiens began to populate all regions of the globe, from America to Australia to Polynesia, often destroying much in its wake. Soon, success of many other species was based almost entirely on its influence on humanity. Nutritious plants such as wheat and rice were cultivated for food, and relatively docile animals such as pigs, cattle and sheep were domesticated for meat. Dogs were domesticated for companionship and protection, while rats, fleas and influenza thrived in increasingly urban human settlements. As humans became more industrious, they extracted the fossilised remains of Lepidodendron from the ground to power their machines. This burning expelled carbon dioxide into the air – the industrial smog disrupting the oxygen-rich atmosphere initially formed by the cyanobacteria that created habitable conditions for complex life over 2 billion years before. The planet began to heat, reversing the carbon-capturing, cooling process performed by Azolla.
Conclusion
Despite incredible advances in computerised climate modelling, we are not certain as to exactly what the future will bring — but we are increasingly understanding the events of the past. We only have one Earth, and its conditions that were favourable for habitable life were produced by a complex and long-winded series of events. It is increasingly important to educate and enact change to save the life that painstakingly evolved on Planet Earth.
Sources
- Allgre, C.J. and Schneider, S. H. (2005) Evolution of Earth, In Scientific American. Retrieved April 20, 2020 from https://www.scientificamerican.com/article/evolution-of-earth/
- Wikipedia contributors. (2020) Abiogenesis, In Wikipedia, The Free Encyclopedia. Retrieved April 20, 2020 from https://en.wikipedia.org/w/index.php?title=Abiogenesis&oldid=951753245
- Al-Khalili, J. and McFadden, J. (2014) Life on the Edge: The Coming of Age of Quantum Biology. London: Bantam Press
- Lloyd, C. (2009) The Story of the World in 100 Species. London: Bloomsbury Press
- Wikipedia contributors. (2020) Cyanobacteria, In Wikipedia, The Free Encyclopedia, Retrieved April 21, 2020 from https://en.wikipedia.org/w/index.php?title=Cyanobacteria&oldid=950337193
- Gore, R. The Rise of Mammals, In The National Geographic. Retrieved May 14, 2020 from https://www.nationalgeographic.com/science/prehistoric-world/rise-mammals/
Before you can have life you need the first living cell, What we are made of is amino acids, lipids, carbohydrates, nucleic acid, all homochiral, you can’t get that in nature, so we were either seeded here or God made us, if we were seeded here it still does not answer where first life came from it just moves its location
All those are found in nature and several have been found in space.
Ridiculous to believe that information could pop into existence. Information requires an information giver,and the system to understand the information. There is no such thing as a simple cell, thousands of exact requirements all there at the same time are required. Life comes only from life
Life only comes from life is equivalent to “All life comes from life” , look :
Premise 1 : all life comes from life
Premise 2 : The first cell is life
Conclusion : Therefore, the first cell come from life
But there is a problem here :
Premise 1 : All life comes from life
Premise 2 : God is life
Conclusion : God comes from life
But God didn’t come from life according to theists, so, either Premise 2 is false (God is not life) or Premise 1 is false (It’s not the case that all life came from life).
To get out of this logical delimma, the theist must say that “God is not life in the same sense as a living sense”, so :
Let’s call God’s life life2 and cell’s life life1
Premise 1 : All life1 comes from life2
Premise 2 : the cell is life1
Conclusion : the cell comes from life2
Now, we are talking .. but the first premise is useless now, since it doesn’t serve our purpose , the main reason why the theist claims that All life comes from life is the observation that all life1 (offspring) comes from life1 (parents), but if they use this premise and include God, then God too is a life1 and needs a parent.
To conclude, this is the source of this equivocation fallacy, in fact : either only some life comes from life, or God came from life, or the first premise would be useless.
100 trillion cells in the body,each with six feet of DNA which would reach many times to the sun with billions of bits of information did not happen by accident
Quantum superposition abiogenesis sounds a lot like cosmic intelligence thinking I want to make life
We know to form one Protien by Chance alone is : 1 to 10^164 because from 200 amino acido only 20 left shape of them can create one Protien.
And also the DNA need the protein and the protein need the DNA in the same time together but the Abiogenesis explained the Protien evolved first and this is in reality not possible.
The probability to arrange single DNA is not possible imagin the number.
The Royal society in London declared they dont know:
1. How life started first time?
2. From where came the genetic code of the DNA?
All those commented here needs more proper books to read and acknowledge. Approximately 4 Billion years ago, there were no life on earth. Earth was impossible to be habitable by complex and evolved organisms like us. Abiogenesis is the key to produce simple molecular structures like phospholipids, simple nucleotides, amino acids, water and other elements like ions and minerals associated together to form a much more complex structure that was known as a cell were created on earth. Thanks to Supernova explosion from nearby stars that has caused a drastic changes to earth. The accretion of our solar system and the uniqueness of our earth to form life on earth is simply just extraordinary as we are alone as a living planet among the others. Abiogenesis is a great fact. Have fun learning and acknowledging about it.
Hi Sunthran. Here is a series that shows how little we actually knownabout abiogenesis. The concept that we are typically presented is very far from the reality of the research. Here is a link to a series of videos you might be interested in. The link is for the first introductory video
https://youtu.be/71dqAFUb-v0
Our knowledge about the behaviors of prebiotic chemistry show that naturalistic Abiogenesis does not happen. Here’s essential research on the subject: https://youtu.be/NqoVxwdWWpg
Well said.
Sad to see so many MYTH believers! That’s one reason we are moving to a human, and other life extinction event!
The myth may not be what you think it is. Here is series of video that gives insight to our true understanding of abiogenesis. It is the for the introduction of a 13 part series.
https://youtu.be/71dqAFUb-v0
James Tour pushes back neatly against the vast tide of fellow PhD ‘s and even Nobel winning colleagues with his presentations. Skeptics will dismiss it as God of the gaps but for those who are open minded it really does highlight the scale of the problem with abiogenisis
The Miller-Urey experiment happened almost 70 years ago and was discredited within the scientific community by the 1980’s. But it is still the best idea out there. Think about how far other areas of science have come since 1952. And the best that abiogenesis has is a failed experiment from 70 years ago. Watch this series to see the real state of abiogenesis research and you will see that how little they really know about how or if it could happen.
The series has 13 parrs this is the introduction.
https://youtu.be/71dqAFUb-v0
Good to see articles about abiogenesis. So ridiculously to say a god did it cause I don’t understand how it happened. Even more ridiculous is the math equation, odds of life forming on earth is 1, cause we are here. The DNA is a code is hilarious, if you think it is a code like computer code share the first five lines of that “code”.
In areas of fundamental ignorance, the questions become a kind of projective test in which we can expose our preconceptions, assumptions, wishes and fears. It’s unclear whether any of those necessarily shed light on the underlying Mystery. Science has been long captivated by 3 nested Mysteries: #1 the emergence of matter and the universe, #2 within that, the emergence of life, and #3 within that, an evolutionary trajectory of some kind towards the emergence of mind. All three of these questions are fundamentally mysterious. One can think of them perhaps as indexing emergent properties – an emergent property is something that cannot be predicted from the science strictly confined to the antecedent level of organization. For example, no amount of understanding of chemical rules of organization allows you to predict that a chemical complex has become self-organizing, self-repairing, and evolves towards greater complexity. In this sense, the hope of hard reductionism may be a Fool’s errand. We may have to accept that there are these emergent properties that have a kind of spooky birthing from a simpler substrate, and where they acquire complexities and features that cannot be explained simply by the substrate. The same kind of analysis applies to the next emergent property, how Consciousness emerges from a biological substrate of the brain. Same problems, same gravitation towards magical thinking, same challenges. That it does emerge seems the one Rock Solid conclusion.
There are many questions about how biogenesis took place but to suggest that God did it is not an explanation. How did God do it? Did he/she materialize life-forms whole and ready made in an existing ecology? It’s so obvious but that is magical thinking. The fact that we cannot replicate DNA, or even for that matter RNA let alone a single cell in the lab is not a reason to abandon a naturalistic explanation for the emergent property. It is however a good reason to be humble in the face of Nature and Nature’s Mysteries. It may take many dozens of scientific lifetimes to unravel the organization of a single and relatively simple form of cell. It may require a much finer understanding of the interdigitating and recursive cascade towards the complexity of a single cell and how this was organized in and emerged from a primordial biochemical space. But magic and magical thinking is not a solution. And the notion that such complexity mandates a designer is nonsense. Who is the designer inside the endlessly variable complexity of a snowflake? Complexity emerges. Nature takes chaos and builds order from the bottom up. Nature reveals a vast and interlinked chain of organization from the microcosm to the macrocosm. We still don’t adequately intellectually respect that complexity, or the emergent properties it generates. The one thing I agree with the theologians about however is the need for more humility, and the results from our lack of humility in the face of Nature are painfully evident.
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God disagrees