<P> In population biology and demography, the generation time is the average time between two consecutive generations in the lineages of a population . In human populations, the generation time typically ranges from 22 to 32 years . Historians sometimes use this to date events, by converting generations into years to obtain rough estimates of time . </P> <P> The existing definitions of the generation time fall into two categories: those that treat the generation time as a renewal time of the population, and those that focus on the distance between individuals of one generation and the next . Below are the three most commonly used definitions: </P>

How long is a human generation in years