How Life Started on Earth

By now we have all become accustomed to the idea that life originated in the ocean. But certain questions still make scientists have fierce arguments with each other. For example, how did life transition from water to dry land? Why would a mass meteorite strike be useful? Is collision with another planet important for the development of life? What did Earth look like throughout the first millions of years of its existence and what obstacles did it have to face? Some of these questions already have answers and we will share them with you right now. Life that originated in the water and later made its way to dry land appears as a very plausible theory. After all, the oceans currently cover more than 70% of the Earth and contain many different organisms. Some of them studied so little that scientists still continue to discover new species. Once on land, these life forms successfully adapted and evolved to eventually become human. Everyone remembers Darwin's theory where a fish suddenly decided to spend its vacation on dry land. The modern scientists explain this theory. Fun fact, no matter how many refutations of Darwin's theory you read, scientists take this theory as a starting point The main question is, what is required for a life to form except for the ocean? To answer this question, we must travel to the distant past of the solar system. The process of creation of the solar system is similar to our neighboring star systems. At some point, about 13.6 billion years ago, the Big Bang happened. According to scientists, it was responsible for creating the universe as we see it in telescopes. And the consequences of this event led to the first chemical elements forming. Hydrogen, which compressed and heated under the pressure of the energy from the explosion, and turned into a new element, helium. We refer to this bunch of compressed hydrogen which turns into helium as a protostar. But the protostars did not stay with us for long. The main benefit of their existence is the emergence of new chemical elements, which became the building blocks for the origin of life. First and foremost, it led to the emergence of ordinary stars. Every star has a life cycle throughout which the star is akin to a factory. Something is burning, there is some smoke, and streams of resources are flowing through to produce something. Simultaneously, all of these processes affect the ecology and environment. So, our sun, like any other star, does the same thing, but on a cosmic scale. And then, the life of a star factory is pretty prosaic. It either expands to a supernova or transforms into a red giant or a dark dwarf, followed by attenuation and death. Alternatively, a star can turn into a black hole. We know for sure that the sun will become a red giant, eventually expanding to encompass nearby planets, including us. However, we still have 5.5 billion years before that happens, so we'll have enough time to finish watching our favorite TV shows. What is so special about our solar system? Scientists theorized that the sun was created by a supernova being destroyed not far from the future solar system. Thus, our star, having arisen from compressed clouds of gases, will have eventually absorbed such a high amount of matter due to gravity that it will be enough not only for its existence, but also for the creation of the entire solar system. Everything that was not a part of the new star began to revolve around it, flattening and acquiring the shape of a disk. That's a huge amount of matter. Some of it will be lucky to become a planet, and some will leave the sun's immediate orbit to become a comet or a dwarf planet. The future cradle of humankind came to existence somewhere around here. At the start of its life, Earth was something like a stew of lava, rocks in a liquid form, and crazy mixtures of gases released during the melting process. Near Earth's surface, the temperature exceeded 1200 degrees. There was no air, only carbon dioxide, nitrogen, and steam. Moreover, the planet was being continuously bombarded by comets and meteorites, some attracted by the planet itself and some attracted by the sun. This is where the water particles that eventually land on Earth come from, but at this point there is no talk of any life. Earth receives the most powerful blow in its history, but also the most useful as it turned out later. A planet the size of Mars, which was later named Theia by the scientists, crashes into us. The result of this collision is the formation of the current shape and size of Earth. But even more importantly, the fragments form into our satellite, the moon. Initially, it was much closer to us, 13.6 thousand miles. This will have an effect later on. The importance of the moon will become more evident as Earth cools down. Over time, Earth's temperature began to lower, which led to Earth's crust forming, a thick layer of everything that our planet collected due to gravity as it was forming. And after the cooling process, only the very core of the planet, molten iron, remained hot and liquid. It is the activity within the core that creates the magnetic field around Earth and keeps it at its stable moving pace, both around its own axis and around the sun. As the temperature kept dropping, the planet experienced its first rainfall. Around 3.8 billion years ago, it was subjected to a meteor shower, the remnants from the formation of the solar system bombarding Earth. But inside these bombs, there was also something useful, namely water. Those are not yet the kind of rains we're used to. At the time, the speed of Earth's rotation was so high that a day only lasted six hours. However, thanks to that very useful rain, the first ocean is formed on Earth. Meteor showers lasted 20 million years, so the low water content in each individual meteorite was not a problem. Quantity led to quality. At this stage in Earth's development, scientists had a question, where did water actually come from? There are two theories regarding this. Some believe that all the water was brought to us by meteorites. A second theory suggests that there was already water on Earth. The argument was solved by time and new discoveries. Both theories turned out to be right and wrong at the same time. Studying the soil from the moon's surface revealed that the then young and active sun burned everything that could evaporate from the planets, including water and gases. And so the scientists still cannot definitively say whether there is more water of meteoric or terrestrial origin present on Earth. And most likely, they will never be able to answer that question. But the main thing is that the collision of Earth and Theia became a catalyst for the beginning of the cooling process of the planets and subsequently the formation of Earth's atmosphere, which would serve to protect it from the sun. The existence of the atmosphere became the shield that maintains everything needed to create life and doesn't let anything harmful in. How did the atmosphere form? Earth has cooled down but the volcanoes are still active. Due to this volcanic activity, water evaporates, turning into clouds, which then turn into rain. For millions of years, rains fall to Earth's surface, pooling into lakes, then seas and oceans. And this worldwide ocean was very stormy. You know how the moon influenced the tide. At the time, the moon was much closer and its rotation around Earth caused such powerful ocean storms we could hardly imagine the scale. Some waves reach no less than a thousand feet in height. Meanwhile, the winds on Earth were nearly as fast as the speed of sound. And so the ocean is raging, the storm is at full swing. Where is life? Contemporary theories generally agree on one thing. Back then, Earth's oceans were an ideal place for the emergence of life. But there are several problems. The main question is how did organic matter, that is chemical elements that are the building blocks of life, come to exist under these conditions? Let's break it down. Water and Earth's atmosphere at the time, specifically nitrogen, hydrogen, and carbon dioxide, are elements from the inanimate part of the chemical elements, the so-called inorganic chemical elements. To answer this, let's look at the theory that was developed by Oparin, an academic from the USSR in 1924, as well as a similar theory put forward by a biochemist from the UK named Haldane in 1938. In essence, these theories are simple. The ocean of that time was constantly replenished with organic substances from the atmosphere, which was constantly struck by lightning thanks to the endless storm of that period. It was under the influence of these electrical charges that these elements in the atmosphere turned from inanimate, inorganic, into living, organic, and fell into the Once they were in the water, the particles slowly gathered together and formed a broth of organic matter, which would subsequently develop into living organisms. The way these particles behave was similar to the behavior of cells. They can grow, divide, and absorb other chemical elements. But the truth is, the organic matter only acts as the building blocks of the body. Creating life itself requires a team of workers and a foreman to bring everything together. The foreman of our cells is our DNA, an entire library of how everything works, from reproduction to building complex structures from sets of cells. The workers performing the task are RNA. The Oparin-Haldane theory is similar to the story about Frankenstein's monster, whose inanimate matter was also brought to life by a lightning strike. The main thing that we know is that life arose somewhere in the ocean and for 300 million years existed in the form of single-celled organisms. They were not particularly in a hurry to turn into people, were they? But to be frank, the conditions of the ancient earth would not have given something more complex a chance to develop. The single-celled organisms that existed then were prokaryotes. The main difference between them and us is that their organism consisted of one cell without a protective membrane, and in most cases without a nucleus. A good example of the currently existing prokaryotes is bacteria. On earth first, oxygen came to exist in sufficient quantities to begin to form the atmosphere in which we now live. And then, within a billion years, somewhere between 3.5 and 2.5 billion years ago, a new miracle took place. Single-celled organisms, even in such a literally toxic atmosphere, have learned to use the energy of light to convert water, carbon dioxide, and solar energy into their first food, glucose. The byproduct of the process produced even more oxygen. We refer to this miracle as photosynthesis. After the cooling of the earth and the formation of the ocean, a terrible thing happened. Two ice ages took place. The first, known as the Pongola glaciation, lasted 500 million years. The second, the Huronian ice age, was slightly shorter, but it almost exterminated life on earth. The Huron glaciation lasted 300 million years. It was caused by an oxygen catastrophe. It happened due to the fact that, thanks to photosynthesis, unicellular organisms began to release so much oxygen that it led to the extinction of all unicellular organisms that existed without oxygen. And so, aerobic organisms, the organisms that need oxygen to exist, became dominant life forms on the planet. Next, prokaryotes continued to evolve into eukaryotes. Both are closest and the most ancient ancestors in terms of cell structure. Eukaryotes were able to compete, absorb, and destroy their own kind. They used solar energy as the main source of life and were also able to reproduce. Eukaryotes gradually moved closer to dry land, formed by volcanic activity, producing more and more oxygen along the way. In the shallow water, they united to form the prototype of underwater trees, stromatolites. First, they became red algae, with their key feature being the ability to reproduce sexually. This skill will give an impetus to evolution, resulting in the next prototype of modern nature, mushrooms that grow on land. 540 million years ago, the Cambrian explosion occurred, characterized by the dramatic increase in the number of living organisms. This event prompted the emergence of future animals, plankton, and calcimicrobes. 70 to 80 million years later, another rapid leap in evolution takes place when most of the species known to us today come to existence. The first animals to set foot on dry land were arthropods. At first, they simply roamed the land in search of more satiating food than algae and plankton, but then they never went back into the water. According to scientists, one of the most interesting species that transitioned from life in water to life on land is the Tiktaalik fish. Its limbs were like paws, which made it possible for them to move out of the water. For 360 million years, plants, having learned to reproduce by seeds, spread across the land and more. The insects will soon fly into the air. Amphibians, having evolved into four-legged tetrapods, remain on dry land, having learned to hide their eggs from predators and eat a variety of foods. In the future, these animals branch out into several species, giving rise to lizards, birds, artiodactyls, and primates. Yet another blow awaited them, the Permian extinction, which killed 90% of water-dwelling species but left many species alive on dry land. It took the ecology about 90 million years to recover. Then there was the era of the dinosaurs that went extinct due to a meteorite impact, but the birds and half of the other species survived. Life has finally conquered the land. Let's sum it up. Earth has a unique combination of factors contributing to the origin of life. The question about the origin of life remains unanswered, but we have some intriguing clues. Water and the world's oceans are the main source of these answers, but not the only source. Our oceans are unique. They are a result of Earth's planetary evolution. We live in a beautiful time when discoveries related to the transformation of inanimate elements into the living matter are closer than ever. We even envy ourselves a little. After all, the secret of life may soon be revealed.