Humanity has always wondered about its own origin and about the origin of life . The answer may never be known, but the human being continues to seek explanations.
If life arises from a preexisting life, how did the first living thing come about? Or, how did the first living being emerge in the Earth’s environmental conditions 3.5 billion years ago? And for this, how was it and in what way can the primitive atmosphere be traced back?
Based on such questions begins the study of the origin of life.
Theory of abiogenesis
Also called spontaneous generation, this hypothesis was defended by Aristotle (384-322 BC) and reflects the thought in antiquity on the subject. According to him, living beings could arise by means of changes in inanimate matter and spontaneously .
Theory of biogenesis
Due to the contestations and discussions at the time, still in the seventeenth century, to a great extent by the contribution of Louis Pasteur , the idea began to be constructed that a living being originates only from another preexisting living being and the theory of abiogenesis was overthrown .
Fixing and creationism
This strand is based on the events described in the book ” Genesis, ” the first of the Holy Bible. According to her, God created all the things that exist on Earth, which are immutable, fixed. He argues, therefore, that the human being and all other living beings do not change over time.
Also known as extraterrestrial hypothesis , it reports that life arose on Earth from living beings similar to the microorganisms currently present on the planet or precursors of life (seeds of life) brought from other places in the cosmos, from another star or star, therefore .
Origin of life by chemical evolution
Life, according to this hypothesis, would have arisen from non-living matter, through associations between molecules and the formation of increasingly complex substances, which have organized themselves so as to give rise to the first being (s) I live.
This hypothesis is very well accepted in the scientific milieu and was proposed in 1924 by Oparin and in 1929 by Haldane. As both scientists agreed in many respects, it became known as the Hypothesis of Oparin and Haldane .
The hypothesis proposed that the first living beings were formed from organic molecules , formed in the atmosphere, and later in the oceans, from inorganic molecules . This hypothesis came from the belief of some scientists who considered the possibility that the first living beings had arisen by a subtle coincidence between the elements present in the primitive atmosphere and the molecules found in living beings
According to Oparin, the primitive atmosphere of Earth was very different from the current one. Although there is no consensus at the time, it was believed that, with volcanic eruptions , constant particles and simple gases were released into the atmosphere as methane (CH4), ammonia (NH3), water (H 2 O) in the form of steam and of hydrogen (H 2 ). Oxygen would be absent or present in very small quantities. These substances would have been subjected, for thousands of years, to electric discharges (rays) originating from violent storms, bombardment of ultraviolet radiation and high temperatures.
The energy from these physical processes would have allowed the formation of the first simple organic molecules. It promoted varied reactions among chemical elements that have accumulated in the oceans, rivers and lakes. The Earth was still in the process of cooling, which allowed the accumulation of water in the depressions of the crust originating the primitive seas.
According to the hypothesis of Oparin and Haldane, simple molecules would be carried away by the rains to the primitive seas and lakes, which were shallow and very hot. In these lakes, the molecules would react and form, over millions of years, a ” nutritious soup “, rich in organic matter, mainly in amino acids and proteins – molecules more complex and fundamental to the beginning of life on Earth