scholarly journals Parental investment and the optimization of human family size

2011 ◽  
Vol 366 (1563) ◽  
pp. 333-343 ◽  
Author(s):  
David W. Lawson ◽  
Ruth Mace
Keyword(s):  
Family Size ◽  
Parental Investment ◽  
Resource Competition ◽  
Reproductive Behaviour ◽  
Reproductive Rate ◽  
Low Fertility ◽  
Individual Level ◽  
Offspring Number ◽  
Adaptive Models ◽  
Fertility Limitation

Human reproductive behaviour is marked by exceptional variation at the population and individual level. Human behavioural ecologists propose adaptive hypotheses to explain this variation as shifting phenotypic optima in relation to local socioecological niches. Here we review evidence that variation in fertility (offspring number), in both traditional and modern industrialized populations, represents optimization of the life-history trade-off between reproductive rate and parental investment. While a reliance on correlational methods suggests the true costs of sibling resource competition are often poorly estimated, a range of anthropological and demographic studies confirm that parents balance family size against offspring success. Evidence of optimization is less forthcoming. Declines in fertility associated with modernization are particularly difficult to reconcile with adaptive models, because fertility limitation fails to enhance offspring reproductive success. Yet, considering alternative measures, we show that modern low fertility confers many advantages on offspring, which are probably transmitted to future generations. Evidence from populations that have undergone or initiated demographic transition indicate that these rewards to fertility limitation fall selectively on relatively wealthy individuals. The adaptive significance of modern reproductive behaviour remains difficult to evaluate, but may be best understood in response to rising investment costs of rearing socially and economically competitive offspring.

scholarly journals Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society

2012 ◽  
Vol 279 (1746) ◽  
pp. 4342-4351 ◽  
Author(s):  
Anna Goodman ◽  
Ilona Koupil ◽  
David W. Lawson
Keyword(s):  
Socioeconomic Position ◽  
Social Inequalities ◽  
Low Fertility ◽  
Industrial Society ◽  
Long Term Effects ◽  
Socioeconomic Resources ◽  
Adaptive Models ◽  
Fertility Limitation ◽  
Socioeconomic Success

Adaptive accounts of modern low human fertility argue that small family size maximizes the inheritance of socioeconomic resources across generations and may consequently increase long-term fitness. This study explores the long-term impacts of fertility and socioeconomic position (SEP) on multiple dimensions of descendant success in a unique Swedish cohort of 14 000 individuals born during 1915–1929. We show that low fertility and high SEP predict increased descendant socioeconomic success across four generations. Furthermore, these effects are multiplicative, with the greatest benefits of low fertility observed when SEP is high. Low fertility and high SEP do not, however, predict increased descendant reproductive success. Our results are therefore consistent with the idea that modern fertility limitation represents a strategic response to the local costs of rearing socioeconomically competitive offspring, but contradict adaptive models suggesting that it maximizes long-term fitness. This indicates a conflict in modern societies between behaviours promoting socioeconomic versus biological success. This study also makes a methodological contribution, demonstrating that the number of offspring strongly predicts long-term fitness and thereby validating use of fertility data to estimate current selective pressures in modern populations. Finally, our findings highlight that differences in fertility and SEP can have important long-term effects on the persistence of social inequalities across generations.

scholarly journals The offspring quantity–quality trade-off and human fertility variation

2016 ◽  
Vol 371 (1692) ◽  
pp. 20150145 ◽  
Author(s):  
David W. Lawson ◽  
Monique Borgerhoff Mulder
Keyword(s):  
Evolutionary Ecology ◽  
Reproductive Behaviour ◽  
Low Fertility ◽  
Human Reproduction ◽  
Trade Off ◽  
Trade Offs ◽  
Human Fertility ◽  
Fertility Variation ◽  
Fertility Limitation ◽  
Economic Perspectives

The idea that trade-offs between offspring quantity and quality shape reproductive behaviour has long been central to economic perspectives on fertility. It also has a parallel and richer theoretical foundation in evolutionary ecology. We review the application of the quantity–quality trade-off concept to human reproduction, emphasizing distinctions between clutch size and lifetime fertility, and the wider set of forces contributing to fertility variation in iteroparous and sexually reproducing species like our own. We then argue that in settings approximating human evolutionary history, several factors limit costly sibling competition. Consequently, while the optimization of quantity–quality trade-offs undoubtedly shaped the evolution of human physiology setting the upper limits of reproduction, we argue it plays a modest role in accounting for socio-ecological and individual variation in fertility. Only upon entering the demographic transition can fertility limitation be clearly interpreted as strategically orientated to advancing offspring quality via increased parental investment per child, with low fertility increasing descendant socio-economic success, although not reproductive success. We conclude that existing economic and evolutionary literature has often overemphasized the centrality of quantity–quality trade-offs to human fertility variation and advocate for the development of more holistic frameworks encompassing alternative life-history trade-offs and the evolved mechanisms guiding their resolution.

scholarly journals Identifying unknown Indian wolves by their distinctive howls: its potential as a non-invasive survey method

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sougata Sadhukhan ◽  
Holly Root-Gutteridge ◽  
Bilal Habib
Keyword(s):  
Reproductive Behaviour ◽  
Identification Accuracy ◽  
Individual Identification ◽  
Survey Method ◽  
Reliable Estimate ◽  
Mark Recapture ◽  
Test Dataset ◽  
Individual Level ◽  
Non Invasive ◽  
Supervised Classification Methods

AbstractPrevious studies have posited the use of acoustics-based surveys to monitor population size and estimate their density. However, decreasing the bias in population estimations, such as by using Capture–Mark–Recapture, requires the identification of individuals using supervised classification methods, especially for sparsely populated species like the wolf which may otherwise be counted repeatedly. The cryptic behaviour of Indian wolf (Canis lupus pallipes) poses serious challenges to survey efforts, and thus, there is no reliable estimate of their population despite a prominent role in the ecosystem. Like other wolves, Indian wolves produce howls that can be detected over distances of more than 6 km, making them ideal candidates for acoustic surveys. Here, we explore the use of a supervised classifier to identify unknown individuals. We trained a supervised Agglomerative Nesting hierarchical clustering (AGNES) model using 49 howls from five Indian wolves and achieved 98% individual identification accuracy. We tested our model’s predictive power using 20 novel howls from a further four individuals (test dataset) and resulted in 75% accuracy in classifying howls to individuals. The model can reduce bias in population estimations using Capture-Mark-Recapture and track individual wolves non-invasively by their howls. This has potential for studies of wolves’ territory use, pack composition, and reproductive behaviour. Our method can potentially be adapted for other species with individually distinctive vocalisations, representing an advanced tool for individual-level monitoring.

scholarly journals Costly children: the motivations for parental investment in children in a low fertility context

Genus ◽  
2021 ◽  
Vol 77 (1) ◽  
Author(s):  
Anne H. Gauthier ◽  
Petra W. de Jong
Keyword(s):  
Parental Investment ◽  
Low Fertility ◽  
Middle Income ◽  
Time Investment ◽  
Investment In Children ◽  
Theoretical Perspectives ◽  
Self Development ◽  
The Usa ◽  
Human And Social Capital ◽  
Large Investment

AbstractWhile the literature has documented a general increase in parental investment in children, both in terms of financial and time investment, the motives for this increase remain unclear. This paper aims at shedding light on these motives by examining parents’ own narratives of their parenting experiences from the vantage point of three theoretical perspectives. In doing so, the paper brings side-by-side the goal of providing children with human and social capital to improve their future labour market prospects, the pressures on parents to conform to new societal standards of good and intensive parenting, and the experience of parenting as part of self-development. The data come from a qualitative study of middle-income parents in Canada and the USA. The results provide some support for each of these perspectives, while also revealing how they jointly help explain parents’ large investment in their children as well as the tensions and contradictions that come with it.

scholarly journals Planning a family in Nairobi’s informal settlements: results of a qualitative study

2019 ◽  
Vol 52 (2) ◽  
pp. 286-299 ◽  
Author(s):  
Catriona A. Towriss ◽  
Donatien Beguy ◽  
Alison Wringe ◽  
Barwako Hassan Hussein ◽  
Ian M. Timæus
Keyword(s):  
Family Planning ◽  
Focus Group ◽  
Family Size ◽  
Reproductive Age ◽  
Low Fertility ◽  
Present Moment ◽  
High Fertility ◽  
Focus Group Discussions ◽  
Group Discussions ◽  
Childbearing Intentions

AbstractChildbearing intentions among women in high-fertility contexts are usually classified into those wanting to have a baby, those wanting to ‘space’ a birth and those wanting to ‘limit’ their family size. However, evidence from Africa increasingly suggests that women’s intentions are more complex than this classification suggests, and that there is fluidity in these intentions. This research explores women’s accounts of their childbearing intentions and decisions in order to examine how this fluidity plays out in a low-fertility context in urban Africa. Six focus group discussions were conducted in April and May 2012 with women of reproductive age in Nairobi, Kenya. Participants were recruited using random and purposive sampling techniques. The focus group discussions had an average of seven participants each. Data were coded thematically and analysed using Nvivo software. The analysis explored the factors that women consider to be influential for childbearing and found that the health of the mother and child, costs of raising a child and relationships were commonly reported to be important. Evidence of intentions to space births and limit family size was found. However, the data also showed that there is fluidity in women’s family planning intentions, driven by changes in relationships or household finances, which often result in a desire to avoid pregnancy in the present moment. The fluidity observed in women’s childbearing intentions cannot be accounted for by the concepts of either ‘spacing’ or ‘limitation’ but is best explained by the concept of ‘postponement’. The research reveals the need for family planning clinics to provide a full method mix, as well as high-quality counselling, to enable women to choose a method that best suits their needs.

Differential paternity in Libya

1987 ◽  
Vol 19 (4) ◽  
pp. 395-403 ◽  
Author(s):  
Mahjoub A. El-Faedy ◽  
Lee L. Bean
Keyword(s):  
Middle East ◽  
Family Size ◽  
Natural Fertility ◽  
High Fertility ◽  
Occupational Groups ◽  
American Frontier ◽  
Fertility Limitation ◽  
Limit Family Size ◽  
Very High

SummaryLibya is one of the Middle East nations with very high fertility, and data from 1973 suggest the presence of a natural fertility regime marked by the absence of fertility limitation within marriage. Analysis of paternity data by occupation, however, identifies major differences in the level and pattern of childbearing. The Libyan data are compared with fertility and paternity data from an American frontier population to demonstrate that the general patterns observed are consistent with other natural fertility populations, while selected occupational groups may limit family size.

Towards a better understanding of past fertility regimes: the ideas and practice of controlling family size in Chinese history

2006 ◽  
Vol 21 (1) ◽  
pp. 9-35 ◽  
Author(s):  
ZHONGWEI ZHAO
Keyword(s):  
Family Size ◽  
Reproductive Behaviour ◽  
Population History ◽  
High Fertility ◽  
Chinese History ◽  
Traditional Beliefs ◽  
The Past ◽  
Demand For Children ◽  
The Impact ◽  
Made In

Thanks to the progress that has been made in the study of population history, it has been gradually accepted that fertility in historical China was only moderate in comparison with the recorded high fertility. However, scholars still disagree on whether the Chinese could have intentionally controlled their family size. This article first summarizes recent findings about fertility patterns in historical China. Then the author provides further evidence of people limiting their family size in the past, before discussing the impact of traditional beliefs on people's fertility behaviour and summarizing the antinatalist ideas and suggestions put forwarded by Chinese officials and intellectuals over China's long history. This evidence is then used to comment on a number of suggestions that have been made about China's traditional reproductive behaviour and culture. The article challenges the views that people's reproductive strategies aimed in the past to maximize the number of surviving offspring and that the demand for children (or sons) was always high in historical China.

scholarly journals Fertility dynamics and reproductive behaviour of men and women entering into marriage in the Republic of Bashkortostan

2021 ◽  
Vol 5 (2) ◽  
pp. 55-75
Author(s):  
Yana A. Skryabina
Keyword(s):  
Reproductive Behaviour ◽  
Fertility Rate ◽  
Low Fertility ◽  
Reproduction Rate ◽  
Fertility Rates ◽  
Expected Number ◽  
Number Of Children ◽  
Reproductive Intentions ◽  
Republic Of Bashkortostan ◽  
The Republic

The article is devoted to the analysis of the fertility rate dynamics in the Republic of Bashkortostan and the study of the reproductive behaviour of the population entering into a registered marriage. The author examines the crude and total fertility rates, the net population reproduction rate, the total fertility rate by the order of births, as well as age-specific fertility rates. In addition, basing on the data of population surveys, the author regards reproductive intentions of citizens applying for marriage in the registry office, as well as reasons that may prevent them from having a child. The study shows that the Republic of Bashkortostan is characterized by a low fertility rate; the generation of children does not replace the generation of parents. The reproductive intentions of the respondents measured by the desired and expected number of children correspond to the small (two-child) family model. Among the main reasons that can prevent the birth of a child, the first two are financial and housing difficulties, and third is the desire to live for oneself for a while.

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