Offspring Human Fertility Behavior in Biodemographic Perspective (2003) / Chapter Skim
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12. Reflections on Demographic, Evolutionary, and Genetic Approaches to the Study of Human Reproductive Behavior
12. Reflections on Demographic, Evolutionary, and Genetic Approaches to the Study of Human Reproductive Behavior
Pages 339-357
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From page 339... ...
The long-standing recognition of the critical importance of both reproductive biology and behavior and their interplays in determining human fertility has been especially clear in the various treatments of the proximate determinants of fertility (Bongaarts and Potter, 1983; Davis and Blake, 1956; Wood, 1994~. In theoretical essence these studies examine variations 339
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From page 340... ...
or childbearing motivation (Miller et al., 2000~. A fairly separate strand of theorizing about fertility and related behavior goes under a variety of labels, including the almost defunct sociobiology, evolutionary psychology, evolutionary anthropology, human behavioral ecology, and gene-environment coevolution; these fields often disagree substantially, but they all grapple with evolutionary aspects of human fertility and related behavior.
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From page 341... ...
How could we distinguish between these two plausible "determinants" of past reproductive behavior? If we are predisposed to reproduce in some direct pronatalist sense, achieving very low fertility would require stronger behavioral desires and controls to offset this innate tendency than if the pathway was through recreational sex (Diamond, 1997; Foster, 2000; Hobcraft and Kiernan, 1995; Morgan and King, 2001~.
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From page 342... ...
Most of the studies on fertility-related behavior to date have relied on standard ACE or DCE models (Additive and Dominant; the latter include a dominant instead of an additive genetic component)
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From page 343... ...
Strong selection for survival is reflected in the small sample sizes for the earliest cohorts (around 600 twin pairs of each sex for the birth cohorts of 1870 to 1889, compared with about 1,400 for those of 1890-1910~. Moreover, the reported fertility for these earliest birth cohorts seems very low and apparently quite out of line with the general population, suggesting either severe misreporting or strong selection of survivors for low fertility.
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From page 344... ...
Kohier and his collaborators are quite comfortable with a very low genetic component of variation for the earliest cohorts considered, seeing this as being compatible with Fisher's fundamental theorem of natural selection for a society with pretransitional fertility levels, since very little genetic variation would be expected for fitness components. Hughes and Burieson (2000)
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From page 345... ...
does not show unequivocally stronger genetic variation than either censored completed fertility or ever having had a birth for the 19531964 birth cohorts. Moreover, there are clearly interplays between behavior and motivation on the one hand and fecundity on the other: delaying childbearing until ages of reduced fecundity can have unintended consequences.
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From page 346... ...
First, twin studies will never permit us to address and disentangle genetic components of variation for the dyed involved. The only way to get leverage on this aspect will be through molecular genetics (or linking back through neuroendocrine protein pathways to genetic markers)
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From page 347... ...
It is striking that a large body of evidence can be reviewed concerning sexual behavior and the biology of fertility, but there seems to be a paucity of evidence on endocrine or neuroendocrine pathways related to the other behavioral aspects of fertility, such as reproductive intentions or motivations, with the exception of nurturance or parental behavior. See Panksepp (1998)
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From page 348... ...
But fertility-related behavior, including pair bonding, coital frequency, contraceptive use, and abortion among others and fertility motivations are much less well understood. This is why serious attempts to outline the pathways involved or the ontogenies are badly required (see Miller and Rogers, 2001, on human bonding; and Foster, 2000, or Miller et al., 2000, on childbearing motivation)
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From page 349... ...
Several authors have drawn attention to the sufficiency of an evolved sex drive among humans, one of the relatively few species to enjoy recreational sex (Diamond, 1997) , to have ensured fertility in traditional societies (Foster, 2000; Hobcraft and Kiernan, 1995; Morgan and King, 2001; Potts, 1997~.
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From page 350... ...
have been much more enthusiastic about incorporating (and sometimes co-opting) the ideas and work of demographers and related social scientists on fertility behavior into their perspectives than demographers have been to grasp evolutionary perspectives or new biological research1 (with a few notable exceptions, e.g., U3ry, 1996~.
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From page 351... ...
A similar role differentiation by gender is a basic postulate of much modern microeconomics theory of the family (Becker, 1981~. Yet, hardly surprisingly, many modern feminists regard such postulates as provocative.
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and behavioral, and the interactions and feedbacks within and between these domains. CONCLUSION Over the next few years we see a highly productive domain of research that links both fertility and fertility-related behavior backward through identifiable pathways and genetically mediated neural and endocrinological pathways forward to fertility-related behavior.
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From page 353... ...
The novel analysis of time trends in the partitioning of components of genetic and sharedenvironment variance components is replicable with long-term demographic registers given modern computer linkage algorithms. But the longer-term horizon demands molecular linkages, especially if the partners are both to be considered.
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From page 354... ...
In Genetic Influences on Human Fertility and Sexuality: Theoretical and Empirical Contributions from tI7e Biological and Behavioral Sciences.
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From page 355... ...
Burleson 2000 Evolutionary causes of genetic variation in fertility and other fitness components. In Genetic Influences on Human Fertility and Sexuality: Theoretical and Empirical Contributions from the Biological and Behavioral Sciences.
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From page 356... ...
Rowe, and W.B. Miller 2001a Genetic influence helps explain variation in human fertility: Evidence from recent behavioral and molecular genetic studies.
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From page 357... ...
Waldron 2000 Nonshared environment: A theoretical, methodological, and quantitative review. Psychological Bulletin 126:78-108.
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