When people think of the meaning of life, they usually ask themselves, how did life even begin? There are many theories on how life began on Earth. But we still do not know for sure how life began. Regardless, there are three more likely theories that can explain the origin of life, but they are not without their flaws.
One of the first theories on how life began on Earth is called the primordial soup theory. This theory states that organic molecules began to synthesize on their own in the Earth’s oceans. In fact, this theory had some early success. In 1952, the Miller-Urey experiment was able to produce the organic molecules that included amino acids. They were able to produce these building blocks of life with only inorganic molecules. They also substituted for the early primitive atmosphere that surrounded Earth. The lighting gave enough gave enough energy off to synthesize organic molecules from elements that were commonly found throughout the planet. Unfortunately, any organic molecules that would form on the surface of the ocean would soon be destroyed by the ultraviolet radiation from the sun. Earth’s early atmosphere did not have an ozone layer to protect the planet from the UV rays from the sun.
Another popular theory is that life was brought to us from meteors that landed on Earth. While this may not sound like a plausible theory since meteors burn upon entry, when a meteor enters Earth’s atmosphere, something surprising happens. The front end of the meteor magnetizes upon entry into the atmosphere and protects that back end from any disturbance that would destroy small molecules. In 2009, the amino acid glycine was found on a comet and is known as one of the fundamental amino acids needed for life. But this theory still does not explain how life was created, but only how it got to Earth. Also, any organic compounds would still have to deal with the UV rays from the sun.
Hydrothermal vent theory is now one of the more widely accepted theories that is currently out there. This is because scientists found an organism that could live under the sea without oxygen called Archaeans. They are also the oldest species that is found on this planet. In fact, some scientists claim that all life on Earth evolved from an early form of Archaea. Most Archaeans cannot live in the presence of oxygen, but give off oxygen as a metabolic by-product. This is because different Archaea feed on methane and sulfur. Hydrothermal vents below the ocean surface release vast amounts of sulfur and Archaeans can still be found in these vents. Archaeans did not have to worry about the UV rays from the sun because they were deep enough in the water to be protected. With these organisms giving off free oxygen, it could be enough to build the ozone layer for other organisms to be created through other processes. Regardless, the question remains, how did these organisms become self-replicating?