What Is Darwin's Four Stage Hypothesis

According to Charles Darwin, the emergence of a new species is a consequence of natural selection acting on existing species. Building upon this idea, the diversity of life must have originated from a few species. Although the details of prehistoric life may never be answered with certainty, evidence from geologic fossils allows us to hypothesize how life began on Earth. In fact, there are many theories as to how life developed, but the most accepted idea is the abiotic evolution of organic molecules from primordial Earth conditions. Details about the nature of this evolution are still debated, but the general idea can be explained in a four-stage hypothesis.
In this four-stage hypothesis, the first stage was the abiotic formation of organic molecules, such as amino acids and nucleotide monomers. The idea that organic molecules can be formed abiotically was based on the fact that the early Earth was abundant with elements necessary to create the modern biological macromolecules. In fact, the famous experiment performed by Harold Urey and Stanley Miller proved that the primordial conditions of the early-Earth can create organic molecules (Simon, Dickey, & Reece 297-298). After the formation of organic molecules, spontaneous processes abiotically synthesized polymers from the existing organic molecules. Then, the polymers and
Comparison of the diverse modern prokaryotes at the molecular level suggests that the prokaryotic evolution must have originated into two branches: Bacteria and Archaea. Therefore, it is believed that all life forms must have originated from this two domain (Simon et al. 298). Moreover, based on the primordial conditions, the first forms of life are chemical heterotrophs. The earliest prokaryotes must have fed from the abundance of organic molecules and