Abstract A computer study of population growth and biological ageing in the Penna model is presented. The stress is put on the analysis of the age structure and the distribution of ‘bad’ mutations m in the population. Results of computer simulation are compared with the simplest logistic model approach which ignores genetic contribution to the life game and accounts only for death due to limited environmental capacity, the Verhulst factor. The Penna model accounts also for genetic load and results of the simulation show that the final population essentially consists of the fittest individuals, as is expected. A more detailed analysis of the genome structure Δ ( m ) discloses significant marks of the history. The main conclusions are: (a) there is a clear correlation between population n , age a and the number m of bad mutations and (b) there is no correlation between particular configurations Δ ( m ) of genomes of the same m and the fraction of the population of this characteristics Δ ( m ). A typical run takes a couple of hours on an HP EXEMPLAR machine, and for a population of about n =10 6 .