'By 70 weeks, before the completion of weaning, a female baboon's lifetime fitness is largely established,' says Altman.

This protection hypothesis is supported by studies of stress hormones in female baboons during changes in the male hierarchy.

However, later studies show female baboons retain close associations with their female kin throughout their lives.

The female baboon displays it on her bottom when she is in estrus.

These mating calls, often low and guttural, are the main criteria, used by the female baboon to determine which male she mates with.

Also, female baboons benefit from increased rank because high-ranking females produce more surviving offspring.

Male baboons leave their mothers; female baboons stay close for life.

The researchers used data from 25 years of observations, taking into account the maternal careers of 138 female baboons with 584 pregnancies among them.

The female baboon had to appear to be in heat, which the researchers simulated by attaching a red plastic mold to her rear.

Groups of female baboons could coerce new male members of the troop into more peaceful behaviors.