From the scientific point of view, emergence of life is a transformation of inert matter into a living organism. Scientists consider that it arose in oceans more than 3.5 billion years ago. Long time Earth was inhabited by monocelled life forms.
To the earth about 5 billion years. The first watch lives on the planet appeared not earlier than 3.5 billion years ago. At the same time it is considered that the human race exists on Earth about 5 million years. Scientists from time immemorial try to recreate the scenario of the events preceding emergence of living organisms.
Theory of self-generation
Throughout the millennia the most part of scientists considered that all live can be generated not only individuals of the same look, but also to arise from plants and even inert matter, for example dirt. It were adherents of the so-called theory of self-generation. In 1862 it was disproved by Louis Pasteur.
The cellular theory, it is the theory of long chemical evolution, it was put forward at the beginning of the 20th century. Scientists came to a conclusion that they are necessary for emergence of a cage formation of components of which it consists – atoms and molecules and also a possibility of their connection with each other. It turns out that emergence of cellular life – result of the long chemical evolution which lasted for many millions of years.
Everything in our Universe consists of a little more than one hundred simple elements, each of which makes one type of atoms, for example carbon, hydrogen, sulfur or oxygen. Thanks to "relationship" or certain conditions the elements can form connections – molecules.
So, table salt, or sodium chloride, represents connection from one atom of sodium and one atom of chlorine. This example is followed from the inorganic world – the lifeless matter incapable of life. In the organic kingdom it is harder and harder: the ability of carbon to form difficult connections is very high, especially in salty water.
Under the influence of a set of power sources, for example sunlight and electric discharges of a lightning, in the atmosphere of Earth small organic molecules arose. They collected in the ocean. Some were attracted to each other, others – made a start.
The event when the difficult molecule had a chemical mechanism allowing not only to maintain the turned-out connection, but also to be restored became turning point in origin of life and even to be reproduced. Emergence of deoxyribonucleic acid (DNA) became result.
Today many scientists consider that DNA – a chemical basis of life on our planet. This molecule has surprising ability to self-reproduction, i.e. creation of own copies. Information transferred by DNA cannot be removed. Emergence of this molecule allowed to transfer information from generation to generation. Development of life on Earth also began with it.