Darwin's theory of evolution believes that natural selection is the main driving force of evolution, while the neutral theory of molecular evolution believes that the main driving force of evolution is genetic drift. Since the evolution of species is a long process compared with the time when humans appeared, it is difficult to verify right and wrong. Therefore, the issue of evolution is still under debate. It is relatively easy for us to explore biological evolution within a limited period of time from the evolution of the composition of the genome. Regarding the evolution of the composition and structure of the genome, this book discusses the following two questions. The first question to be discussed is the effect of the high mutation rate of CpG mutation to TpG/CpA caused by the methylation of vertebrate genome on the evolution of genome composition. The second question is whether the GC content in the human genome has reached an equilibrium state.