Top 10 theories of the origin of life

Planet earth is estimated to have existed for 4.55 billion years. For its part, life as we know it appears to have arisen approximately one billion years later. But where exactly does it come from? This question has been asked by philosophers and scientists for many centuries and has given rise to different theories about its origins.

In Western culture, these theories have their foundation, either in Christianity or in science. In this sense, the proposals range from the will of a divine being to the evolution of our genetic material, going through the interventions of cosmic material and the composition of matter inert. In this article we will review 10 of the main theories about the origin of life on Earth.

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10 theories about the origin of life

As we have said, theories about the origins of life on earth range from the proposals of Christianity to the most complex scientific hypotheses; largely developed by the physical, chemical, and biological sciences. We present below a tour of these proposals.

1. Theory of creationism

The most widespread biblical narrative on the origins of life suggests that it occurred through the intervention and will of a divine being. In the book of genesis, within the old testament, it is explained that this being was dedicated to generating the different states and living beings as we know them. In the course of seven days, he created the sky and the earth, to later originate the light, the darkness, the seas, the vegetation, the sun and the moon, the animals; the man and the woman; and finally, he rested.

This is the theory that has been most current in western societies through the centuries, until the advances in research inherited from the Scientific Revolution questioned it.

• You may be interested: "Creationism: what it is and why it causes controversy"

2. Theory of genesis under the ice

One of the proposals about the origins of life on earth is that billions of years ago, the oceans were completely covered by a very thick layer of ice. Being such a thick layer, that even measures hundreds of meters, it was possible that the organic compounds were very well protected from external agents, and from the sun itself, which was previously much more powerful given the planet's conditions land.

So that, the strong protection of the ice sheet was able to generate a safe interaction of microorganisms, and finally create life forms.

3. Theory of electrical activity

Broadly speaking, this theory proposes that electrical currents can produce simple amino acids and sugars, from different simple chemical compounds found in the atmosphere. In this sense, life would originate as consequence of the presence of lightning that, when coming into contact with the elements of the earth's atmosphere, it may have been responsible for originating the first and most basic forms of life.

4. Panspermia

Panspermia proposes that life on earth began from rocks, meteorites, and remnants of cosmic material that have impacted our planet since its first moments of existence. This material is supposed to be transported through cosmic dust, and kept on earth by gravity. Panspermia proposes that the existence of these remains could generate the organic and bacterial material necessary to generate life. It was first raised by the German biologist Hermann Ritcher in 1865.

5. Spontaneous generation

Spontaneous generation is one of the oldest and best known theories about the origins of life. Broadly speaking, he proposes that life is generated spontaneously or naturally from microorganisms present in inert matter. In its oldest forms, the theory of spontaneous generation considered that life is created because some inert materials can give rise to living organisms (for example, manure generate flies).

In this context, the experiment carried out by the Italian doctor Francesco Redi, who tried to prove that inert matter does not generate life, but attracts it, is classic. What he did was leave a piece of meat exposed, and another piece of meat inside a closed jar. He verified that flies did not arise from meat, but from eggs left by other flies when it was in the open. Finally, it was Louis Pasteur who verified that microorganisms do not arise from inert matter but are in the air, and that matter only attracts them.

6. Abiogenesis theory

Reformulating the spontaneous generation theory, the theory of abiogenesis has emerged, which proposes that there is a natural process in inert matter from which life arises. For example, it is proposed that life on earth began when water vapor was finally able to condense, because this generated geochemical and astronomical processes that in turn originated the genome minimum. From this it follows that spontaneous generation could have been a real process, but millions of years ago (not in the current state of our planet).

Likewise, the abiogenesis theory suggests that life was generated by different chemical reactions that gradually allowed the most primitive organisms to evolve.

7. Underwater suction cup theory

Deep in the ocean are hydrothermal vents, also known as hot spring vents or underwater hydrothermal vents. These are crevices and fumaroles that allow steam and hot water to pass through. These vents have very extensive ecosystems. According to this theory, the nutrient-rich ocean environment, together with reactive gases, was able to create the habitat necessary to generate the first life forms.

In other words, the origins of life as we know them could take place inside hydrothermal vents; This question also takes up the proposals on what could have happened under the ice sheets that previously covered the oceans.

8. RNA (and protein) theory

Ribonucleic acid is the compound that is currently considered crucial in the organization and expression of our genetic material. It works together with deoxyribonucleic acid, DNA, transferring and systematizing the vital information that the latter generates. It is a kind of messenger for DNA and has the ability to regulate itself more automatically. The theory of the generation of life that is explained through RNA, says that it occurred by a spontaneous outbreak of RNA on our planet.

Given this, an important question has emerged: what came first: RNA or proteins? Some theories postulate that without the synthesis of the latter, the RNA could not have emerged, much less spontaneously; since the most basic components of proteins are too complex.

• You may be interested: "Differences between DNA and RNA"

9. Theory of genesis under the mud

There is also the proposal that life on earth evolved from the concentration of mud. This is the case since said concentration could serve as an area of ​​condensation of chemical activity; which could finally give rise to a kind of "breeding ground" for the components necessary to generate genetic material (DNA and RNA).

10. Theory of metabolism

In contrast to the theories of RNA, the theories of metabolism say very broadly that the Chemical elements and atmospheric nutrients simply continued to react through the weather, producing increasingly complex molecules. Thus, gradually, it gave rise to the first forms of life and later to life as we know it.

Bibliographic references:

• Marshall, M. (2016). The secret of how life on earth began. BBC. Retrieved July 10, 2018. Available in http://www.bbc.com/earth/story/20161026-the-secret-of-how-life-on-earth-began.
• Futurism (2015). Abiogenesis: 7 scientific theories for the origin of life… and one new one! Retrieved July 10, 2018. Available in https://futurism.com/abiogenesis-7-scientific-theories-origin-life-one-new-one/.
• Daminelli, A. & Santa Cruz, D. (2007). Origins of life. Advanced Studies 21 (59): 263-285.