Preference for sons and sex ratio in two non-Western societies.

Moroccan Berbers and the Bolivian Aymara are two unrelated peasant groups living in adverse environments with a still rather traditional agriculture. Precarious life conditions may be responsible for the importance given to male labor and hence for the cultural preference conferred on male descent. This preference, expressed in the social valorization of sons to the detriment of daughters, is more emphasized if the socioeconomic status of the family is lower.

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.

Reproduction in high altitude Aymara: physiological stress and fertility planning?

Reproductive characteristics at high altitude are described based on the reproductive histories of 720 Aymara women, collected in 1998 and 1999 in a group of twelve peasant communities at a mean altitude of 4000 m in the Bolivian Altiplano. The reproductive pattern is shaped by a late onset of childbearing, associated with a rather short reproductive span and large birth intervals. Environmental conditions could explain the particularly late age at menarche of rural girls compared with their urban counterparts, whereas the age at first birth is likely to be under cultural control.

Helping patterns and reproductive success in Aymara communities.

"Helpers at the nest," young adults remaining in their parents home to take care of younger siblings, are known in many species of birds and mammals. Similar behaviors are occasionally observed in human societies but their frequency and significance for parental reproductive success are still not fully appraised. This study was designed to document this issue in a traditional Aymara peasant society of the Bolivian Altiplano, It is based on 359 reproductive life histories of women 45 years of age or older and on a survey of children's workload in 1998 and 1999.

Do "helpers at the nest" increase their parents' reproductive success?

"Helpers at the nest," usually offspring of a preceding litter who contribute by feeding the young to increase the reproductive success of a breeding pair, are known in many species of birds and mammals. Although similar behaviors were described by ethnological observations in several human societies, there is a lack of data on their existence and role. This study of 794 reproductive life histories of post-menopausal Berber women of Southern Morocco aims to provide such information.