Rebecca Sear et al.
Kin influences on fertility: A theoretical framework tested with a review of the literature
Rebecca Sear (London School of Hygiene And Tropical Medicine) & Cristina Moya (LSHTM)
The presented paper has been removed at the request of the authors
I agree with the Discussant comments that this is a very ambitious paper and that it might serve the authors and the readers well to consider limiting the scope (e.g. fewer fertility outcomes) or breaking it up into two papers. This is simply too dense of a paper to reach a wider audience.
As a family demographer, I am wondering how to understand these findings in light of other demographic processes such as union formation & dissolution which are both influenced by kin and have effects on fertility decision making.
Two, I am also curious how reproductive mishaps may affect these processes? Here I am thinking about Caroline Bledsoe’s “maternal depletion” idea.
Just some thoughts that came to mind while reading a fascinating paper.
Thanks
Thank you for your feedback. It will be most helpful in developing these manuscripts further.
I agree that these should be turned into separate articles, in part because the data available from the review does not match the various hypotheses we develop particularly well.
The theoretical piece started as an attempt to help organize our thinking about the review, but its purpose has shifted to clarifying that several predictions about kin effects on fertility outcomes are not as clear cut as many evolutionary social scientists make them out to be. This may help explain the number of “dots” or non-directional predictions in Table 1. Often times people make evolutionary predictions based on unexamined, or demographically unrealistic, assumptions. For example, it is common to assume that higher fertility enhances fitness – i.e. long term number of descendants, or that women prefer having fewer children than men because this maximizes their fitness – despite the average fitness of men and women being equal.
There are many good reasons to expect other social influences on fertility, as the reviewer notes, but these are beyond the scope of the current project. More to the point, perhaps we have to justify better why we chose to discuss the moderators of kin effects that we have chosen to highlight.
Sangeetha, while we are not investigating union formation and dissolution, I think this may be a problem for interpreting the differences between parental and in-law effects, since the latter only exist once individuals are married. Given some models of intergenerational conflicts we’ve been building we might actually expect parents to delay their childrens’ marriages (using their children’s labour for their own benefit), but have no such delaying effect on their reproduction once they are married. Parental effects on union formation may also be particularly important in societies with bridewealth and dowry requirements, and thus have downstream effects on first births, something we are trying to test in another project. We are somewhat lazily assuming that age at union and first birth are strongly correlated, which is more realistic in natural fertility populations.
Re: mishaps and maternal depletion, if I understand the concepts correctly we allude to it some in the discussion of sexual antagonism. That is men who can replace their spouses might be more willing to pursue a reproductive strategy that is suboptimal for the woman (i.e. depletes her resources and does not contribute to parental care). I tend to think that the degree of this sexual antagonism has been exaggerated or misunderstood in the evolutionary community, but my collaborators often disagree with me about this.
A very simple point – what about the sex of the child; is that not an important factor that should have found a place in the equation.
I agree with the other points raised below about the social context. expected family?Husband/wife stability.
Many thanks to the discussant for her detailed comments – this is very much a work in progress and all these comments will be very helpful in further developing the paper. Comments from a family demographer are especially helpful at this stage – as we do want this to reach a wide audience, but are aware that some of our concepts will not be particularly familiar to some demographers.
Just to pick up on one point raised by the discussant – I would be particularly interested in investigating women’s other (non-kin) social networks, and how these might influence her fertility behaviour. Particularly in light of Turke and Newson’s suggestions that the demographic transition may be facilitated by the loosening of kin ties and increasing significance of non-kin networks, which are assumed to be less helpful and less pro-natal than kin networks – though this assumption is rarely tested. I am not yet sure, however, how to gather data on, and analyse, women’s non-kin networks. Data on kin availability is relatively common, but information on the content of social networks which include non-kin appears to be much more rare. Any suggestions here would be gratefully received!
To Sangeetha – many thanks also for your comments. As Cristina says, we are giving serious thought to dividing up the paper into a theoretical piece and an empirical review – your comments and those of the discussant suggest this is definitely the way to go!
Union formation is certainly an important part of the story – we perhaps need to highlight this in the theoretical section. Unfortunately for the empirical review, there appear to be fewer studies on parental influences on marriage than on fertility though we perhaps need to look more carefully through the literature to find them.
On reproductive mishaps – do you mean that they might blur any observed relationship between kin and fertility? Or that part of the explanation for kin effects might be that kin are influential in protecting women from them, or causing them? (Jan Beise & Eckart Voland have suggested that mothers-in-law cause a higher incidence of stillbirths/neonatal deaths by stressing out their daughters-in-law, in their paper using historical German data sub-titled ‘The husband’s mother is the devil in the house’, apparently an old German proverb)
To Esther – do you mean that kin influences on inter-birth interval might vary by the sex of the child opening the interval? Very few studies have looked at this – but see the paper below for one example:
Johow, J.; Fox, M.; Knapp, L. A.; Voland, E. (2011): The presence of a paternal grandmother lengthens interbirth interval following the birth of a granddaughter in Krummhörn (18th and 19th centuries), Evolution and Human Behavior 32 (5) 315–325
This has been a terrific exchange. Thank you again for the opportunity to read your paper, and I look forward to hearing how it evolves.