Reproductive success: which meaning?

The theory of kin selection (the part played by behavior in the changes of mean inclusive fitness) induced many human sociobiologists to think that since behavior was involved in the increase in fitness, this last entity could apply to the individual. Approximated by the individual's lifetime reproductive success, this measure became the keyword of studies linking social and cultural behavior to biological adaptive processes. To be commonly applicable to human populations, it had to be simplified to represent the number of offspring reaching sexual maturity and most existing studies are based on this definition. The current trend, however, seems to consider that, like inbreeding, reproductive success takes its signification in the depth of successive generations. These diverse measures were tested in two traditional populations, Berber and Aymara, and show that finding a satisfactory evaluation of reproductive success is a problem that is still far from a solution.