  Much information is stored in amino acid composition of protein and base
composition of DNA. We simulated the evolution of amino acid frequencies and
genomic GC content by a linguistic model. It is showed that the evolution of
genetic code determines the evolution of amino acid frequencies and genomic GC
content. We explained the relationships among amino acid frequencies, genomic
GC content and protein length distribution in a unified theoretical framework.
Especially, the simulations of the evolution of amino acid frequencies and the
codon position GC content agree dramatically with the results based on the data
of all known genomes so far. Furthermore, we found that the space of average
protein length in proteome and ratio of amino acid frequencies is useful to
describe the phylogeny and evolution. Amazingly, the dots of all the species in
this space form an evolutionary flow. We believe that the amino acid gain and
loss is motivated by the established pattern of the variation of amino acid
frequencies. The linguistic mechanism is helpful to unveil the origin of the
genetic code.
