3. How are self-replicating molecules, such as RNA molecules in the “RNA World” hypothesis, essential to the most popular hypotheses about the origin of life on Earth
There are at least three types of hypotheses which attempt to explain the origin of life on Earth. The first and oldest of these hypotheses suggest that life was created by a supreme being or spiritual force. The second one states that life began in another part of the universe and arrived on Earth by chance. The third, and most common hypothesis in the scientific community, is that life began approximately 3.5 billion years ago as the result of a complex sequence of chemical reactions that took place spontaneously in Earth's atmosphere. All of the mentioned hypotheses state that life appeared once and then could develop by its own. It means that living organisms or organic molecules had to replicate by their own in order to support their further existence. Therefore, DNA and RNA molecules which are capable of self-replication were required for the processes of reproduction and life support on the Earth.