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Are all grandmothers equal? A review and a preliminary test of the “grandmother hypothesis” in Tokugawa Japan
Author(s) -
Jamison Cheryl Sorenson,
Cornell Laurel L.,
Jamison Paul L.,
Nakazato Hideki
Publication year - 2002
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.10070
Subject(s) - grandparent , demography , population , test (biology) , civilization , genealogy , psychology , kinship , developmental psychology , history , sociology , biology , anthropology , paleontology , archaeology
An unresolved question arising from human evolutionary research relates to the function of the postreproductive period in human females. If menopause is not merely an artifact resulting from the benefits of civilization, there must be an adaptive mechanism favoring the offspring of women who continue to thrive well past the time of their last ovulation. The “grandmother hypothesis” was developed on the basis of the original suggestion by Williams (1957 Evolution 11: 32–39) that “stopping early” would benefit already‐born children. This idea, combined with the concepts of kin selection (Hamilton 1964 J Theor Biol 7: 1–52) and parental investment (Trivers 1972 Sexual Selection and the Descent of Man, Chicago: Aldine, p. 136–179), was expanded to suggest that postreproductive women (in contrast to males) contribute to their inclusive fitness by extending support to their grandchildren. We used discrete time event history analysis (Allison [1984] Event History Analysis, Newbury Park: Sage; Allison [1995] Survival Analysis, Cary, NC: SAS Institute) and logistic regression on data provided in population registers ( Shūmon Aratame Chō , or SAC) from a village in central Japan, covering the period from 1671–1871, in a preliminary investigation of the effects of household grandparental presence on the probability of a child's death. We found that after accounting for the presence of other household members, the only grandparent whose presence exerted a consistent negative effect on the likelihood of a child's death was the mother's mother. Due to the small sample size of households that contained maternal grandmothers, these results failed to achieve statistical significance. Their importance, however, is in what they suggest about future research, i.e., census data from preindustrial societies can provide a basis for testing evolutionary proposals, including the “grandmother hypothesis.” Am J Phys Anthropol 119:67–76, 2002. © 2002 Wiley‐Liss, Inc.