RNA World Hypothesis
The Meteorite Theory
Hydrothermal Vents
So Who is Correct?
So how did DNA and RNA get here? We know that all living things have a common code for self-replicating life that controls how cells function, called DNA. The RNA World hypothesis states that perhaps RNA was here first. RNA can help DNA replicate, or copy itself. Some scientists pose that small segments of RNA could have formed from simpler molecules and continued to replicate, paving the way for DNA.
More recently, scientists have discovered amino acids in meteorites that landed on Earth. These amino acids could have been the source of life on Earth and suggest that life was not created on Earth but was, instead, delivered from outer space.
Some scientists believe that early organic molecules arose from hydrothermal vents deep in the ocean. These cracks in the ocean floor release large amounts of hot water. This water is full of minerals and compounds that could have contributed to early life.
We may never know for sure. What we do know is that these small chains of molecules eventually formed longer and longer chains, fueling the organic compounds needed for life. These chains are called polymers and are made up of many monomers linked together. This process, called polymerization, is a necessary step for self-replicating life.