Resources and reproductive success in women with an example from the Kipsigis of Kenya

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73315/1/j.1469-7998.1987.tb03722.x.pd

Early maturing Kipsigis women have higher reproductive success than late maturing women and cost more to marry

Demographic analyses from 3 cohorts of Kenyan Kipsigis women married between 1940 and 1973 demonstrate that early maturing women have higher reproductive success than do late maturing women, due to longer reproductive lifespans and higher fertility. This result is independent of confounding effects of husband's wealth, but not of the wealth of a woman's parents which affects both menarcheal age and subsequent reproductive success. Data on bridewealth payments at 194 marriages occurring after 1959 show that men make higher marriage payments for early maturing women than for late maturing women. Together these results suggest that Kipsigis men vary their marriage payments in accordance with the reproductive value of their brides. The question of why men use age at menarche rather than bride's parents' wealth as a cue to their bride's subsequent reproductive performance is discussed in the light of changing social and economic conditions experienced by Kipsigis since the late 1920s.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46888/1/265_2004_Article_BF00292097.pd

Erratum to ‘Bateman's principles and human sex roles’

Publisher PDFPeer reviewe

The offspring quantity-quality trade-off and human fertility variation.

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

Sending children to school: rural livelihoods and parental investment in education in northern Tanzania

Evolutionary and economic models of the demographic transition argue that economic development incentivizes low-fertility, high-investment parental strategies, and that such strategies emerge first in relatively wealthy families within populations undergoing 'modernization'. However, most research focuses on fertility reduction rather than shifting parental investment, and few studies consider how parental decisions regarding educational investment vary in relation to alternative rural livelihoods. Using data from 19 villages and 1,719 children (7-19 years), we investigate the effects of diversifying livelihoods, wealth and child characteristics on multiple measures of educational investment in rural Tanzania. Children in (predominantly Maasai) pastoralist households were the least likely to attend school, while neighboring farmers and business owners invested more in education. Household wealth, as measured by asset ownership, was also independently positively associated with educational investment for all livelihood types. These results are consistent with lower opportunity costs and greater perceived economic pay-offs to education for relatively labor market-integrated and wealthy households. However, among pastoralists wealth held in livestock was not associated with educational investment This result may reflect elevated opportunity costs related to the child labor demands of livestock herding. We find a marginal female advantage in education, which is surprising because qualitative research and numerous development projects in the region emphasize the disadvantages facing girls. We also find suggestive evidence of a later-born disadvantage (i.e. borderline statistically significant) consistent with the predicted consequences of sequential household resource dilution. Female advantage and later-born disadvantage were particularly evident in the wealthiest households. Greater reliability in the returns to education for wealthy households may favor preferential treatment of children with higher perceived long-term payoffs, while equal but lower-level investment in all children in relatively poor families may reflect a bet-hedging strategy. We discuss our results in light of parental investment theory and the wider literature on the demographic transition. (C) 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Lions, Bylaws, and Conservation Metrics

African lions are a significant threat to pastoralists, triggering both retaliatory and nonretaliatory killings that represent a high-profile example of human-wildlife conflict. In the present article, we report on a grassroots campaign to reduce such conflict by shifting agropastoralists' attitudes toward lion killing and the central role of bylaws in its apparent success. Insofar as all of East Africa's principal protected areas still harboring lions are surrounded by pastoralist populations, the vast majority of which persecute lions, this novel strategy is of considerable wide-scale and practical significance. We report on an estimated 59%-69% reduction in the number of lions killed since the implementation of bylaws and use our experiences to highlight the need for fresh dialog among project managers, conservation organizations, and their funders in crafting appropriate conservation success metrics. In the context of human-wildlife conflict, changes in peoples' norms and attitudes are of greater significance over the long term than simplistic tabulations of the number of individuals saved

Integrating evolutionary theory and social-ecological systems research to address the sustainability challenges of the Anthropocene

The rapid, human-induced changes in the Earth system during the Anthropocene present humanity with critical sustainability challenges. Social-ecological systems (SES) research provides multiple approaches for understanding the complex interactions between humans, social systems, and environments and how we might direct them towards healthier and more resilient futures. However, general theories of SES change have yet to be fully developed. Formal evolutionary theory has been applied as a dynamic theory of change of complex phenomena in biology and the social sciences, but rarely in SES research. In this paper, we explore the connections between both fields, hoping to foster collaboration. After sketching out the distinct intellectual traditions of SES research and evolutionary theory, we map some of their terminological and theoretical connections. We then provide examples of how evolutionary theory might be incorporated into SES research through the use of systems mapping to identify evolutionary processes in SES, the application of concepts from evolutionary developmental biology to understand the connections between systems changes and evolutionary changes, and how evolutionary thinking may help design interventions for beneficial change. Integrating evolutionary theory and SES research can lead to a better understanding of SES changes and positive interventions for a more sustainable Anthropocene. This article is part of the theme issue 'Evolution and sustainability: gathering the strands for an Anthropocene synthesis'

Wealth Transmission and Inequality among Hunter‐Gatherers

We report quantitative estimates of intergenerational transmission and population-wide inequality for wealth measures in a set of hunter-gatherer populations. Wealth is defined broadly as factors that contribute to individual or household well-being, ranging from embodied forms such as weight and hunting success to material forms such household goods, as well as relational wealth in exchange partners. Intergenerational wealth transmission is low to moderate in these populations, but is still expected to have measurable influence on an individual’s life chances. Wealth inequality (measured with Gini coefficients) is moderate for most wealth types, matching what qualitative ethnographic research has generally indicated (if not the stereotype of hunter-gatherers as extreme egalitarians). We discuss some plausible mechanisms for these patterns, and suggest ways in which future research could resolve questions about the role of wealth in hunter-gatherer social and economic life