Studying the number of lineages through Monte Carlo simulations of biological ageing

We studied different versions of the Penna bit-string model for biological ageing and found that, after many generations, the number of lineages N (maternal family names) always decays to one as a power-law N proportional to t(-x) with an exponent z roughly equal to one. Measuring the mean correlation between the ancestor genome and those of the actual population we obtained the result that it goes to zero much earlier before the number of families goes to one, the population keeping thus its biological diversity. Considering maternal and paternal family names (doubled names) we also finished with only one pair of common ancestors. Computing the number of families of a given size as a function of the size (number of individuals the family has had during its whole existence) again a power-law decay is obtained.