There are several different theories written about the origins of life by researchers, scholars, and enthusiasts using whatever evidence is present, the rest of it is covered by logic. Up to seven theories on origins of life prevail as of now; let us have a look at them:
Some theories hold lightning responsible for starting life. Electric sparks are known to produce amino acids and sugars from the atmosphere, which is already loaded with methane, hydrogen, water, and ammonia. The well-known Miller-Urey experiment in 1953, reported that lightning may have created the building blocks that are key to life on this Earth.
Later on, larger and more complex elements were produced. However, a lot of research now suggests that the Earth in the ancient times had low levels of hydrogen. The levels were poor enough to not be able to contribute to life formation. There is still a theory which states that the clouds of the volcano had generous levels of methane, ammonia, and hydrogen in them, and it was probably filled with lighting as well.
Life May have started on clay
Alexander Graham Cairns-Smith, an organic chemist at the University of Glasgow, suggested that the molecules that started life may have met on clay. The clay concentrated the organic compounds together and also helped organize them into patterns which now resemble our genes.
Cairns-Smith further states that possibly the mineral crystals in the clay could have organized the organic molecules into proper patterns. After some time, the organic molecules started doing those tasks themselves.
The deep-sea vent may have been responsible
The deep-sea vent theory states that life probably began in the submarine hydrothermal vents. It is said that these submarine hydrogen vents expelled out key hydrogen-rich molecules.
The rocky nooks then concentrated the molecules and provided for mineral catalysts that created critical reactions. These vents are known to sustain thriving ecosystems even today.
A cold open
Researchers state that ice was responsible for forming oceans. The sun was about a third less luminous than today and thus allowed the oceans to form. The thick layer of ice might have protected the delicate organic compounds from the ultraviolet light of the sun. The cold may have helped the molecules to survive longer which allowed the key reactions to happen much later.
Since DNA and protein depend on each other equally to form, it was the RNA which allowed the two components to be produced. The DNA was able to succeed RNA because they were much more efficient.
This doesn’t mean that RNA does not exist anymore, it still performs some key functions like acting as an on and off switch for some of the genes. The question then arises as to how the RNA came to be. A lot of the scientists say that they just arose, but that theory is still debated.
Theories suggest that instead of a complex story like that of RNA, life may have begun due to a cycle of reactions in which molecules interacted with one another. These reactions produced more molecules which were larger and more complex in nature, and that they performed this reaction better.
Somewhere in space
Panspermia is notion that life probably did not even start on Earth. Life was formed by components from different parts of space coming together. For example, rocks that have been regularly blasted off from Mars, due to cosmic impacts, have been found on Earth, along with Martian meteorites.
Researchers believe that it is these elements from Mars that contained the microbes that made us. The other scientists say that it is possible that life transferred to Earth through the use of comets. However, if this were true then we would have to ask that how did life begin anywhere else in space.