How did life originate on Earth? The details are unknown to mankind, but the cornerstone principles have been established. There are two main theories and many minor ones. So, according to the main version, the organic components came to Earth from outer space, according to another, everything happened on Earth. Here are some of the most popular teachings.
Panspermia
How did our Earth come about? The biography of the planet is unique, and people are trying to unravel it in different ways. There is a hypothesis that the life that exists in the universe is distributed with the help of meteoroids (celestial bodies intermediate in size between interplanetary dust and an asteroid), asteroids and planets. It is assumed that there are life forms that can withstand the effects of vacuum (radiation, vacuum, low temperatures, etc.). They are called extremophiles (including bacteria and microorganisms).
They fall into the debris and dust that are thrown into space aftercollisions of planets, thus preserving life after the death of small bodies of the solar system. Bacteria can travel at rest for an extended period of time before another random collision with other planets.
They can also mix with protoplanetary disks (dense gas cloud around a young planet). If in a new place "persistent but sleepy soldiers" fall into favorable conditions, they become active. The process of evolution begins. The history of the origin of life on Earth is unraveled with the help of probes. Data from instruments that have been inside comets indicate that in the vast majority of cases, the likelihood is confirmed that we are all "a little alien", since the cradle of life is space.
Biopoiesis
And here is another opinion on how life began. On Earth there is living and non-living. Some sciences welcome abiogenesis (biopoesis), which explains how, in the course of natural transformation, biological life emerged from inorganic matter. Most amino acids (also called the building blocks of all living organisms) can be formed using natural chemical reactions that are not related to life.
This confirms the Muller-Urey experiment. In 1953, a scientist ran electricity through a mixture of gases and produced several amino acids in laboratory conditions that mimic those of the early Earth. In all living beings, amino acids are transformed into proteins under the influence of the custodians of the genetic memory of nucleic acids.
The last ones are synthesizedindependently by biochemical means, and proteins accelerate (catalyze) the process. Which of the organic molecules is the first? And how did they interact? Abiogenesis is in the process of finding an answer.
Cosmogonic trends
This is the doctrine of the origin of life in space. In a certain context of space science and astronomy, the term refers to the theory of creation (and study) of the solar system. Attempts to gravitate toward naturalistic cosmogony do not stand up to scrutiny. First, the existing scientific theories cannot explain the main thing: how did the Universe itself appear?
Secondly, there is no physical model that explains the earliest moments of the existence of the universe. In the mentioned theory, there is no concept of quantum gravity. Although string theorists (string theory says that elementary particles arise as a result of the vibrations and interactions of quantum strings), exploring the origin and consequences of the Big Bang (loop quantum cosmology), do not agree with this. They believe they have formulas to describe the model in terms of field equations.
With the help of cosmogonic hypotheses, people explained the uniformity of motion and composition of celestial bodies. Long before life appeared on Earth, matter filled all space and then evolved.
Endosymbiont
The endosymbiotic version was first formulated by the Russian botanist Konstantin Merezhkovsky in 1905. He believed that certain organellesoriginated as free-living bacteria and were taken into another cell as endosymbionts. Mitochondria evolved from proteobacteria (specifically Rickettsiales or close relatives) and chloroplasts from cyanobacteria.
This suggests that multiple forms of bacteria entered into symbiosis with the formation of a eukaryotic cell (eukaryotes are cells of living organisms containing a nucleus). Symbiotic relationships also contribute to the horizontal transfer of genetic material between bacteria.
The emergence of a variety of life forms may have been preceded by the Last Common Ancestor (LUA) of modern organisms.
Spontaneous generation
Until the early 19th century, people generally dismissed "suddenness" as an explanation for how life began on Earth. The unexpected spontaneous generation of certain forms of life from inanimate matter seemed implausible to them. But they believed in the existence of heterogenesis (a change in the method of reproduction), when one of the forms of life comes from another species (for example, bees from flowers). Classical ideas about spontaneous generation boil down to the following: some complex living organisms appeared due to the decomposition of organic matter.
According to Aristotle, this was an easily observable truth: aphids arise from dew that falls on plants; flies - from spoiled food, mice - from dirty hay, crocodiles - from rotting logs at the bottom of reservoirs, and so on. The theory of spontaneous generation (refuted by Christianity) has secretly existed for centuries.
It is generally accepted that the theory wasfinally refuted in the XIX century by the experiments of Louis Pasteur. The scientist did not study the origin of life, he studied the appearance of microbes in order to be able to fight infectious diseases. However, Pasteur's evidence was no longer controversial, but strictly scientific.
Clay Theory and Sequential Creation
The emergence of life on the basis of clay? Is that possible? A Scottish chemist named A. J. Kearns-Smith from the University of Glasgow in 1985 is the author of such a theory. Based on similar assumptions by other scientists, he argued that organic particles, being between the layers of clay and interacting with them, adopted the way of storing information and growing. Thus, the scientist considered the “clay gene” to be primary. Initially, the mineral and the emerging life existed together, and at a certain stage they "ran up".
The idea of destruction (chaos) in the emerging world paved the way for the theory of catastrophism as one of the predecessors of the theory of evolution. Its proponents believe that the Earth has been affected by sudden, short-lived, turbulent events in the past, and that the present is the key to the past. Each next catastrophe destroyed the existing life. The subsequent creation revived her already different from the previous one.
Materialist doctrine
And here is another version of how life originated on Earth. It was put forward by the materialists. They believe that life appeared as a result of stretched in time andspace of gradual chemical transformations, which, in all likelihood, took place almost 3.8 billion years ago. This development is called molecular, it affects the area of deoxyribonucleic and ribonucleic acids and proteins (proteins).
As a scientific trend, the doctrine arose in the 1960s, when active research was carried out affecting molecular and evolutionary biology, population genetics. Scientists then tried to understand and validate recent discoveries regarding nucleic acids and proteins.
One of the key topics that stimulated the development of this field of knowledge was the evolution of the enzymatic function, the use of nucleic acid divergence as a "molecular clock". Its disclosure contributed to a deeper study of the divergence (branching) of species.
Organic
About how life appeared on Earth, supporters of this doctrine argue as follows. The formation of species began a long time ago - more than 3.5 billion years ago (the number indicates the period in which life exists). Probably, at first there was a slow and gradual process of transformation, and then a fast (within the Universe) stage of improvement began, a transition from one static state to another under the influence of existing conditions.
Evolution, known as biological or organic, is the process of changing over time one or more inherited traits found in populations of organisms. Hereditary traits are special distinguishing features,including anatomical, biochemical and behavioral, which are passed from one generation to another.
Evolution has led to the diversity and diversification of all living organisms (diversification). Our colorful world was described by Charles Darwin as "endless forms, the most beautiful and the most wonderful." One gets the impression that the origin of life is a story without beginning or end.
Special creation
According to this theory, all forms of life that exist today on planet Earth are created by God. Adam and Eve are the first man and woman created by the Almighty. Life on Earth began with them, believe Christians, Muslims and Jews. Three religions agreed that God created the universe in seven days, making the sixth day the culmination of labor: he created Adam from the dust of the earth and Eve from his rib.
On the seventh day God rested. Then he breathed life into people and sent them to look after the garden called Eden. In the center grew the Tree of Life and the Tree of the Knowledge of Good. God allowed the fruits of all the trees in the garden to be eaten, except for the Tree of Knowledge (“for on the day you eat them you will die”).
But the people disobeyed. The Qur'an says that Adam offered to taste the apple. God forgave sinners and sent both of them to earth as his representatives. And yet… Where did life come from on Earth? As you can see, there is no single answer. Although modern scientists are increasingly inclined towards the abiogenic (inorganic) theory of the origin of all living things.
