Grandparental co-residence and grandchild survival in a pre-industrial population

Although grandparents are and have been important alloparents to their
grandchildren, they are not necessarily only beneficial but can also
compete with grandchildren over limited resources. Competition over
parental care or other resources may exist especially if grandparents live
in the same household with grandchildren and it can be dependent on
grandchild age. By utilising demographic data collected from historic
population registers in Finland between 1761 and 1895 (study sample n =
4041) we investigate whether grandparents living in the same household
with grandchildren are detrimental or beneficial for grandchild survival.
Having a living but not co-residing grandmother or grandfather were both
associated with better survival whereas having a co-resident grandfather
was associated with lower chance of survival for infants (age < 1
year). Separating the effect between maternal and paternal grandparents
and grandmothers and grandfathers revealed no differences in the effects
between lineages. Negative effect of having a co-residing grandfather was
not significant when grandfathers were separated for lineage-specific
models. These results implicate that accounting for the co-residence
status and child’s age, grandparents were mostly beneficial when not
co-residing with very young children and that having a co-residing
grandfather at that age could be associated with lower chances to survive.
Predictions made by grandmother hypothesis and resource competition both
received support. The results presented here also offered comparison
points to preindustrial and contemporary three-generational families.