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

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

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Cultural group selection and the design of REDD+: Insights from Pemba

Evolutionary analyses of the ways humans manage natural resources have until recently focused on the costs and benefits of prudent resource use to the individual. In contrast, the fields of environmental resource management and sustainability focus on institutions whereby successful practices can be established and maintained, and the extent to which these fit specific environmental conditions. Furthermore, recent theoretical work explores how resource conservation practices and institutions can emerge through co-evolutionary processes if there are substantial group-level benefits. Here we examine the design of a prominent yet controversial institutional intervention for reducing deforestation and land degradation in the developing world (REDD+), and its ongoing implementation on Pemba Island (Zanzibar, Tanzania) to determine the extent to which the features of REDD+ might allow for the endogenous adoption of sustainable forest management institutions. Additionally, we consider factors that might impede such outcomes, such as leakage, elite capture, and marginal community participation. By focusing on prospective features of REDD+ design that could facilitate the spread of environmentally sustainable behavior within and between communities, we identify distinct dynamics whereby institutional practices might coevolve with resource conservation practices. These insights should contribute to the design of more effective forest management institution in the future

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

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

Rates of ecological knowledge learning in Pemba, Tanzania: Implications for childhood evolution

Humans live in diverse, complex niches where survival and reproduction are conditional on the acquisition of knowledge. Humans also have long childhoods, spending more than a decade before they become net producers. Whether the time needed to learn has been a selective force in the evolution of long human childhood is unclear, because there is little comparative data on the growth of ecological knowledge throughout childhood. We measured ecological knowledge at different ages in Pemba, Zanzibar (Tanzania), interviewing 93 children and teenagers between 4 and 26 years. We developed Bayesian latent-trait models to estimate individual knowledge and its association with age, activities, household family structure and education. In the studied population, children learn during the whole pre-reproductive period, but at varying rates, with the fastest increases in young children. Sex differences appear during middle childhood and are mediated by participation in different activities. In addition to providing a detailed empirical investigation of the relationship between knowledge acquisition and childhood, this study develops and documents computational improvements to the modelling of knowledge development