How was life born on earth? The details are unknown to humanity, but the cornerstones are established. There are two main theories and many secondary ones. So, according to the main version, organic components came to Earth from 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 try to solve it in different ways. There is a hypothesis that life existing in the Universe is spread by 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 airless space (radiation, vacuum, low temperatures, etc.). They are called extremophiles (including bacteria and microorganisms).
They fall into debris and dust that are released into space after collisions of planets , thus preserving life after the death of small bodies of the solar system. Bacteria can travel at rest for a long period of time until the next accidental collision with other planets.
They can also mix with protoplanetary disks (a dense gas cloud around a young planet). If in a new place “persistent but sleepy soldiers” find themselves in favorable conditions, they become active. The process of evolution begins. The story of the origin of life on Earth is solved with the help of probes. Data from instruments that have been inside the comets indicate that in the vast majority of cases, the probability that we are all “a little aliens” is confirmed, since the cradle of life is space.
Biopoiesis
And here is another opinion on how life began. There is living and nonliving on Earth. Some sciences welcome abiogenesis (biopoesis), which explains how biological life emerged from inorganic matter in the course of natural transformation. Most amino acids (they are also called the building blocks of all living organisms) can be formed using natural chemical reactions that are not related to life.
This is confirmed by the Mueller-Yuri experiment. In 1953, the scientist passed electricity through a mixture of gases and received several amino acids in laboratory conditions that mimic the conditions of the early Earth. In all living things, amino acids are transformed into proteins under the influence of the guardians of the genetic memory of nucleic acids.
The latter are synthesized independently by the biochemical method, and proteins accelerate (catalyze) the process. Which of the organic molecules is the first? And how did they get in touch? Abiogenesis is in the process of seeking an answer.
Cosmogonic trends
This is the doctrine of the origin of life in space. In a specific context of space science and astronomy, the term refers to the theory of the creation (and study) of the solar system. Attempts to gravitate to naturalistic cosmogony do not hold water. Firstly, existing scientific theories cannot explain the main thing: how did the universe itself appear?
Secondly, there is no physical model explaining the earliest moments of the existence of the universe. The above theory lacks the concept of quantum gravity. Although string theorists (string theory says that elementary particles arise as a result of vibrations and the interaction of quantum strings), investigating the origin and consequences of the Big Bang (loop quantum cosmology) do not agree with this. They believe that they have formulas to describe the model in the framework of field equations.
Using 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 some organelles arose as free-living bacteria and were taken into another cell as endosymbionts. Mitochondria evolved from proteobacteria (in particular, 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 the 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 nucleation
Until the beginning of the 19th century, people generally denied “surprise” as an explanation of how life began on Earth. The unexpected spontaneous generation of certain life forms 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). The classical concepts of spontaneous generation are as follows: some complex living organisms appeared due to the decomposition of organic substances.
According to Aristotle, this was an easily observed truth: aphids arise from dew that falls on plants; flies - from spoiled products, mice - from dirty hay, crocodiles - from rotting logs at the bottom of ponds and so on. The theory of spontaneous generation (refuted by Christianity) has secretly existed for more than one century.
It is believed that the theory was finally refuted in the 19th 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 in nature.
Clay Theory and Sequential Creation
The emergence of clay-based life? Is it possible? A Scottish chemist named A.J. Cairns-Smith from the University of Glasgow in 1985 is the author of such a theory. Based on similar assumptions of other scientists, he argued that organic particles, being between the layers of clay and interacting with them, adopted a way of storing information and growth. Thus, the scientist considered the “clay gene” primary. Initially, the mineral and the nascent life existed together, but at a certain stage they “ran away”.
The idea of destruction (chaos) in the emerging world paved the way for the theory of catastrophism as one of the forerunners of the theory of evolution. Its supporters believe that the Earth in the past was affected by sudden, short-lived, turbulent events, and the present is the key to the past. Each subsequent catastrophe destroyed existing life. The subsequent creation revived it already different from the previous one.
Materialistic teaching
And here is another version regarding how life was born on Earth. It was put forward by the materialists. They believe that life appeared as a result of the gradual chemical transformations stretched in time and space, which, in all likelihood, occurred almost 3.8 billion years ago. Such a development is called molecular, it affects the field of deoxyribonucleic and ribonucleic acids and proteins (proteins).
As a scientific trend, the doctrine arose in the 1960s, when active research was carried out involving molecular and evolutionary biology, and the genetics of populations. Scientists then tried to understand and confirm 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 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 origin
Proponents of this doctrine argue about how life appeared on Earth. The formation of species began a long time ago - more than 3.5 billion years ago (the figure indicates the period in which life exists). Probably, at first there was a slow and gradual transformation process, and then the fast (within the Universe) stage of improvement began, the 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 transmitted from one generation to another.
Evolution has led to the diversity and diverse development of all living organisms (diversification). Charles Darwin described our colorful world as "endless forms, the most beautiful and most wonderful." One gets the impression that the birth of life is a story without a beginning and an end.
Special creation
According to this theory, all life forms 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, - say Christians, Muslims and Jews. The three religions agreed that God created the universe within seven days, making the sixth day the culmination of labor: He created Eve from the dust of the earthly Adam and from his rib.
On the seventh day, God rested. Then he breathed life into people and sent to look after a 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 the day that you eat them will die").
But people disobeyed. The Qur'an says that Adam suggested trying an apple. God forgave sinners and sent both 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 to the abiogenic (inorganic) theory of the origin of all living things.