The theory of evolution is actually divided into two parts—or almost two separate theories—that explain the emergence, development, and evolution of life on this earth. The ﬁrst part, or the ﬁrst theory, is concerned with explaining the emergence of the ﬁrst life, or the origin of life on the earth from nonliving matter. The second part, or the second theory, is concerned with explaining the evolution and development of life from that ﬁrst seed. So it makes sense for us to discuss
the origin of life ﬁrst, and after that we will turn to the discussion of development.
First: The Theory of Abiogenesis (The First Seed)
Biologists believe that each living cell contains the secret of material life by which replication, growth, and reproduction occur. That secret is the chromosome, the location where information is stored. The chromosomes carry DNA, consisting of non-homogeneous sequences of four different nucleotides (A-T-C-G). These four types of nucleotides represent the letters of the genetic language that are used for writing and storing information. The information is copied during the replication process when DNA is duplicated. Therefore, DNA can be considered the component that represents life, because it carries information for replicating itself and producing proteins, and therefore results in reproduction and growth. Variation can occur as a result of the mixing of male and female DNA, or due to mutations that occur specifically during the duplication process, or in some cases, due to radioactive bombardment. Another nucleic acid, known as RNA, is used as a mediator for transmitting information during DNA replication and protein production.
The information in DNA is read by RNA and translated into either a new copy of DNA so that reproduction can occur, or into protein chains that affect the shape and behavior of the cell so that growth can take place. So what makes liver cells different than intestinal cells is the genes that were expressed as a plan for their construction. These pieces of information, or genes, are written in a law-abiding way, and in a precise language, in order for the meaning to reach RNA. Then, either DNA replication takes place, or protein chains are produced. Therefore, we have factories and an industry based on a law-abiding, linguistic plan (i.e. the information, or genes).
There is more than one hypothesis or theory of abiogenesis. One theory is that a group of meteors carrying amino acids struck the earth billions of years ago and a primordial soup of left-handed amino acids formed in the water on the earth. Then, either a self-replicating protein or RNA happened to form. Another theory is that chemical materials that self-replicate emerged ﬁrst, until we reached life, or DNA.