Hola friends. Welcome to another post and a new series of The Scientific Revelation. After having chronology of the universe we will start to understand our planet with the History of Earth, a brand new series, and our first post will tackle the very first chapter in the earth’s story. The formation of the earth and the origin of life is probably the most important event for us as it had started everything for us as a species. previously our sole concentration was on “the chronology of the universe” and its last post was the formation of the solar system and earth. Go check it out and other posts of this series.
4.5 billion years ago earth formed shortly after the formation of the solar system. Once the molten ball of gas changed and gradually cooled into what we have today. From prokaryotes to eukaryotes, from single-celled to multiorgan, from simple life to complex diversified life we have crossed billions of years. Let’s discuss the first chapter of life in detail.
We are all connected; To each other BIOLOGICALLY, to the earth CHEMICALLY, to the Universe ATOMICALLY.
Neil DeGrasse Tyson
The formation of the earth
Shortly after the birth of the solar system earth formed through a series of events. Because the earth is a part of inner rocky planets it is full of heavier metals like iron, nickel, manganese, and others. Because of powerful solar winds, hydrogen and helium were swapped away towards the outer solar system and became the main constituents of gas giants. The most famous hypothesis of planet formation goes like this. 99% of the solar system’s mass was taken by the sun and the rest of that spread across the accretion disk. The bits of dust and rocks had combined together to form planetesimals. These planetesimals collided together to form planets. The protoplanets were bombarded with comets that had increased their mass. After millions of years, this accretion disc dispersed and planets rose from the depths of solar hell.
To know about planet formation refer to my previous blog post The formation of the solar system.
When these protoplanets formed there were at least 100s of them revolving around the sun. These planets went on a Collison course with each other, smashing each other out and blasting the material back in space. Some of them were thrown out of the solar system or became moons of the major planets. Their debris contributed to the mass increment of major planets around the sun.
Hadean and collision with Theia
Since the formation of the earth, we entered in Hadean eon. Welcome to the hellish earth with surface temperature over 2000 degrees F/ 1093 degrees Celsius and carbon dioxide, nitrogen, water vapor, and other toxicities encircling the planet. The simplest description of the earth is like it was a ball of lava. There are many videos of volcanic eruptions on youtube or some of you might have seen a lava river for real. When lava flows, red and hot covering the entire surface. The part that comes in contact with air turns black before being split open by inner heat and lava. This was how early earth behaved during Haden eon.
Theia and moon
At this same time earth collided with Theia, a Mars-size planet. It was an iconic event and it formed the moon. This is a proposed hypothesis to explain the formation of the moon and there is no evidence found supporting it, yet. The earth was big enough to hold onto itself unlike Theia that turned into pieces, some of them were swallowed by the earth and some formed a ring around the earth. Luckily there was no life on earth at that time or else nothing would have survived. This collision had shaken the planet to the core disrupting everything. In other extinction events, life was able to bounce back because nothing had gone extinct 100% but this collision could have destroyed everything.
The debris and rocks in the ring aggregated with each other to form our moon which was closer than today and is gradually moving away. 4 billion years ago sun rose and set in 3 hours day cycle that means 6 hours a day. Earth’s fast movements were slowed down by the moon’s gravity.
The appearance of water and atmosphere
3.9 billion years ago meteors bombarded the earth and probably brought life and water to this new planet. The solar system was quite young and still turbulent at that time. Asteroids were roaming and falling here and there that were left after the formation of the solar system. The most popular idea is that water was bought to earth by meteors. Earth had no atmosphere and water vapor was in a gaseous form that could not condense in liquid. The magnetic field of the earth was still in process. When the magnetic field came to action earth had enough water. Magnetic field had sustained the water and atmospheric gases before they evaporated. The meteor shower of 3.9 billion years lasts long 20 million years.
Though there are some loopholes to this story. The oldest known fossil of life on earth is 3.9 billion years old and had recovered from Australia. It has some lining structure on the rock that might be of the prokaryote bacteria family. This discovery creates some issues because if water was absent on earth at that time how these bacteria grew.
It can also strengthen the theory that life on earth arrived from outer space. In recent times many researchers are believing that maybe life doesn’t need water to originate. Life on earth originated in periodically dry and wet conditions and it used chemical energy for sugar formation rather than solar energy. Do tell me if you want a detailed post on this new emerging idea about the origin of life. Now as the oceans formed the whole face of earth changed, from a bare planet to a planet with water and a stable atmosphere.
Now we can start the new section of the history of earth which will tackle the origin of life. The oldest fossil found in Australia suggests that life originated around 3.9 billion years ago. The bacterial remains found in the rock was a sensational discovery. Many argued that life on earth arrived from other planets. At that time earth was having regular meteor showers and scientists have also found the oldest impact craters in Australia. But there are many researchers who support the genesis on earth idea where life originated near hydrothermal vents at the depth of oceans.
Scientists have also found carbon compounds related to bacteria in older rocks like in Greenland 3.8 billion years ago. Many researchers support that life might have started by the combination of both events. Hydrothermal vents were common at that time. They had provided perfect chemicals and temperature for life to kick start. The early life had no chlorophyll and couldn’t do photosynthesis. So, it had gotten energy from the Geochemical activities of the earth. The early meteor shower had provided ample water for life to form and grow.
The history of the origin
We don’t have to look far back in time to see radically different ideas than today regarding life. Modern science and biology have only got a head start recently. A few centuries ago and even now people believe that God had created all living organisms in the world. I want to avoid any discussion of religion here so we shall only look into biological proves about life. So, as I was saying this prevailing thought of life by god got challenged as scientists looked for proves.
It was common thinking for ages that humans have life energy/biotic energy. They are different from nonliving things which is absolutely true. God had made us and gave us life. This theory got favor because only living creatures have blood and urea. However, the theory of Vitalism first questioned when in 1828 German chemist Friedrich Wohler made urea from ammonium cyanate. Urea was thought to be only found and made by living things. This finding contradicted vitalism and made people realize that living doesn’t have any extra kind of energy. It was just the start of new radical ideas about life.
The theory of evolution
The next and one of the greatest theories of biology is undoubtedly the “Theory of evolution” proposed by Charles Darwin in 1859. In his 30s Darwin aboard HMS Beagle had extensively traveled south America. He on the way had collected fossils as well as got many ideas for his later theories. On this voyage, he landed on Galapagos and came across flinches. He was fascinated by how finches have different beaks according to the island. These finches had beaks as per the food supply on specific islands. They originated from the one common species of flinch and as the food shortage happened these flinches diversified into different species taking up various niches and food habits.
Natural selection and survival of fittest
In the start, Darwin thought they are different species as they looked so radically different. Darwin coined The theory of Evolution in his later years. The “Theory of evolution” coined by darwin says that all species have evolved through trial and error from the previous species. There have to be a predecessor and successor of the species. Through natural selection, species undergo various environmental stresses. Every individual is different and one that is fittest/adaptable survives these stresses. Natural selection favors its genes to future generations eliminating others. The theory of evolution went against the normal notion of that time (god had created every being) for which Charles Darwin had to face heavy criticism.
The origin of species rose as a standard for biology and had changed everything for the best. Charles Darwin had also proposed that life might have started in a warm little pond full of chemicals and all essentiality for life, like sunlight and heat.
The next most important step for understanding how life evolved was the discovery of DNA. This has revolutionized biology and helped us understand life on the cell level, from where everything started 3.8 billion years ago. Francis crick and James Watson had found the double helix structure of DNA and the race to understand life speed up from thereon.
The constituents of life
There are many elements essential for life like DNA, fats, sugars, proteins, and other nucleic acids. Firstly it was thought that protein carries the genes from one generation to the next. But, after experiments on simple viruses and bacteria, we found that DNA carries the gene not protien.
After the discovery of the DNA double helix model, we found out that DNA has two strands in-between. There are two types of nitrogenous bases purines(adenine and guanine) and pyrimidines (cytosine and thymine). DNA tells the cell how to make protein. Protein is everything as it will make organs, muscles, and bones. This information of how to make a protein that in turn will make the body and its function transfer from generation to generation. They can be modified and mutated along the way resulting in a completely different body and functions. We also have RNA in the picture that transfer information from DNA to cells and act as a facilitator. RNA is very important as many think that life started with RNA because many early life forms have it as genetic material. Still, in many viruses, we have RNA for carrying their genes.
Scientists are in an argument that what came first cell membrane or reproduction ability or energy metabolism. All of these are very important in life. The cell membrane was needed for keeping everything inside. Without energy no cell function could happen including reproduction and reproduction was necessary for transferring information. Maybe they all derived together or from a structure even simpler than any of them.
The possible ways life started
There are many possible ways life could have formed on earth most notable one being that it may have started on earth near hydrothermal vents, where optimal chemical energy and components were present. The other theory says that life might have come from outer space. Maybe we are Martians or bacteria cells that came abroad a comet from another solar system of another galaxy.
Some theorists suggest that lightening in early earth produced certain compounds essential for life. The constant volcanic eruptions pumped out toxic gases into the atmosphere which in return created a blanket of clouds. Constant lightning created enough heat for some compounds to form and broke some into simpler constituents.
Some scientists have even proposed that life started near-polar regions. Researchers suspect that life formed near hydrothermal vents and ice had protected it from the harmful solar radiation. Solar radiations were high because the earth had no solid atmosphere back then. Scientists have found one suspected bacterial fossil in Greenland that is 3.8 billion years old which also strengthens this hypothesis.
you can refer to How did life Arise on earth by Live Science.
- Again I would like to refer to Britannica.com Life- the origin of life.
- One of the best, literary one of the best documentaries I have seen on earth and its past. Watch The history of the earth- How our Planet formed.
- Another great documentary on youtube that made all the differences; The whole history of the earth and life.
- A post on the origin of life by American Scientist.
- A very detailed post by BBC Earth on The secret of how life began on earth. This post had covered all past discoveries, studies, and prevailing thoughts about the beginning of life.
- If you want just an introductory knowledge of Life on earth refer to this post on The origin of life.
These are the prevailing thoughts now and as science will improve so these ideas. We have come far away from the origin. The first thing to remember is that life formed in a still unknown place and by an unclear mechanism. We are going back in time to understand life by snapshots of fossils. We have come a far way from accepting that God had made us to actively finding how we originated. Many discoveries had shed light on our quest and many are still waiting to be revealed. This the end of the first chapter in the “History of Earth”. In the next issues, we will discuss more important events that shaped and transformed earth as a planet and diversified life as we know it. Until then stay tuned and do the Revelation.
Please do let me know if you guys want a post on certain topics that I have not covered. Do comment your thought and ideas so I can improve myself.
“Earth is what we all have in common”
Originally published at https://www.thescientificrevelation.com on December 11, 2020.