Methods of the statistical physics used by geneticists to simulate evolution of genes, genomes and populations are described by biologists. In the first part, biological interpretation of some parameters in the Monte Carlo methods used to simulate age structured populations are described. The authors show how to model the demographic structure of the ancient and contemporary human populations and how to use the Monte Carlo model to predict the life span of humans in the near future, explain why women live longer than men and how the higher babies’ mortality can be determined by the genotypes evolving in the finite environment. In simple simulations they have also shown the speciation effect in the physically separated populations. In the second part, the Monte Carlo methods have been used to simulate evolution of nucleotide sequences of genes under directional mutational pressure. It has been shown how the gene inversion- a very frequent phenomenon in the bacterial genomes-helps to rescue genes from selection pressure and increases biodiversity of the genetic  information.