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

Abstract

"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. Results show that the presence of "probable helpers" in the household is related to higher fertility scores and is associated with improved survival of offspring to sexual maturity. In contrast to sparse observations from other human societies, there is no indication that child caretaking would be specific to eldest daughters. Although the association between offspring survival and helping patterns seems highly probable, there is no confirmation that child caretaking per se is the relevant variable. Contrary to nonhuman helpers at the nest, workloads of children range from housekeeping to light agricultural tasks, and are not focused on assisting younger siblings. The improvement of reproductive success is probably the result of multiple interactions, among which the network of kinship would play a role at both the levels of economy and reciprocal assistance.

Girl helpers and time allocation of nursing women among the Toba of Argentina

“…Compounds in NamQom are close together and bound by networks of assistance and exchange, such that young girls' time allocation is determined at the level of the kinship network and not the household (see also Crognier et al 2001). Thus while some girls with no sisters were often bound Kitty's SD Aldine Human Nature Vol.…”

“…In fact their activity budget was similar to that of women living without any dependent children, suggesting that girl helpers might reduce some of the costs to women of having children (Caldwell 1983;Lee and Bulatao 1983;Turke 1988). However, little is known about the behavioral mechanisms through which women effectively "recycle" the contributions of older daughters in the household into the production of more offspring (Crognier et al 2001;Turke 1987).…”

The effects of kin on female fertility in rural Gambia

“…A recent study of a Moroccan Berber population has shown that probable helpers (i.e. older siblings) improved not only child survival rates but also fertility rates of women (Crognier et al, 2001). Other studies have suggested that the siblings of the woman herself may affect her fertility rates (Hill & Hurtado, 1996;Bereczkei, 1998;Draper & Hames, 2000), though siblings may not necessarily be beneficial.…”

Historia Reproductora Y Fecundidad De Las Mujeres Chilenas De Tierra Del Fuego

“…1.91, n= 168), siendo 3 el nú-mero de hijos vivos más habitual y el rango entre 0 y 11 hijos, con un intervalo intergenésico medio de 3.30 años. Comparado con poblaciones contemporáneas, el valor es inferior al de otras poblaciones en desarrollo, con valores mayoritariamente superiores a los 5 hijos por mujer (a modo de ejemplo: North et al, 2000;Crognier et al, 2001) y superior al de las sociedades occidentales actuales. La distribución del número de hijos nacidos vivos de las mujeres de la población muestra, como aspecto más destacable, que las mujeres con 2, 3 y 4 hijos nacidos vivos representan el 69.6% de las mujeres encuestadas en Tierra del Fuego, porcentaje especialmente elevado si lo comparamos con los resultados disponibles de otras poblaciones, donde representan entre el 43.5% y el 50.2% (Bertranpetit, 1981;Cavalli-Sforza and Bodmer, 1981;Luna, 1981).…”