Jeffrey Winking

Inflammation and infection do not promote arterial aging and cardiovascular disease risk factors among lean horticulturalists.

Background Arterial aging is well characterized in industrial populations, but scantly described in populations with little access to modern medicine. Here we characterize health and aging among the Tsimane, Amazonian forager-horticulturalists with short life expectancy, high infectious loads and inflammation, but low adiposity and robust physical fitness. Inflammation has been implicated in all stages of arterial aging, atherogenesis and hypertension, and so we test whether greater inflammation associates with atherosclerosis and CVD risk. In contrast, moderate to vigorous daily activity, minimal obesity, and low fat intake predict minimal CVD risk among older Tsimane. Methods and Findings Peripheral arterial disease (PAD), based on the Ankle-Brachial Index (ABI), and hypertension were measured in Tsimane adults, and compared with rates from industrialized populations. No cases of PAD were found among Tsimane and hypertension was comparatively low (prevalence: 3.5%, 40+; 23%, 70+). Markers of infection and inflammation were much higher among Tsimane than among U.S. adults, whereas HDL was substantially lower. Regression models examine associations of ABI and BP with biomarkers of energy balance and metabolism and of inflammation and infection. Among Tsimane, obesity, blood lipids, and disease history were not significantly associated with ABI. Unlike the Tsimane case, higher cholesterol, C-reactive protein, leukocytes, cigarette smoking and systolic pressure among North Americans are all significantly associated with lower ABI. Conclusions Inflammation may not always be a risk factor for arterial degeneration and CVD, but instead may be offset by other factors: healthy metabolism, active lifestyle, favorable body mass, lean diet, low blood lipids and cardiorespiratory health. Other possibilities, including genetic susceptibility and the role of helminth infections, are discussed. The absence of PAD and CVD among Tsimane parallels anecdotal reports from other small-scale subsistence populations and suggests that chronic vascular disease had little impact on adult mortality throughout most of human evolutionary history.

Why do men marry and why do they stray

Humans are quite unusual compared to other great apes in that reproduction typically takes place within long-term, iteroparous pairings—social arrangements that have been culturally reified as the institution of marriage. With respect to male behaviour, explanations of marriage fall into two major schools of thought. One holds that marriage facilitates a sexual division of labour and paternal investment, both important to the rearing of offspring that are born helpless and remain dependent for remarkably long periods (provisioning model). And the other suggests that the main benefits which men receive from entering into marriage derive from monopolizing access to womens fertility (mating effort model). In this paper, we explore extramarital sexual relationships and the conditions under which they occur as a means of testing predictions derived from these two models. Using data on mens extramarital sexual relationships among Tsimane forager–horticulturists in lowland Bolivia, we tested whether infidelity was more common when men had less of an opportunity to invest in their children or when they risked losing less fertility. We found that Tsimane men appear to be biasing the timing of their affairs to when they are younger and have fewer children, supporting the provisioning model.

A Bioeconomic Approach to Marriage and the Sexual Division of Labor

Children may be viewed as public goods whereby both parents receive equal genetic benefits yet one parent often invests more heavily than the other. We introduce a microeconomic framework for understanding household investment decisions to address questions concerning conflicts of interest over types and amount of work effort among married men and women. Although gains and costs of marriage may not be spread equally among marriage partners, marriage is still a favorable, efficient outcome under a wide range of conditions. This bioeconomic framework subsumes both cooperative and conflictive views on the sexual division of labor. We test hypotheses concerning marriage markets, assortative mating, and men’s labor motivations among Tsimane forager-horticulturalists of Bolivia and find that: (1) men and women both value work effort in marital partners, (2) marital labor contributions are complementary, (3) work effort is correlated between spouses, (4) total production is correlated with total reproduction, and (5) better hunters have higher fitness gains within marital unions.

Learning, menopause, and the human adaptive complex.

This paper presents a new two‐sex learning‐ and skills‐based theory for the evolution of human menopause. The theory proposes that the role of knowledge, skill acquisition, and transfers in determining economic productivity and resource distribution is the distinctive feature of the traditional human ecology that is responsible for the evolution of menopause. The theory also proposes that male reproductive cessation and post‐reproductive investment in descendants is a fundamental characteristic of humans living in traditional foraging and simple horticultural economies. We present evidence relevant to the theory. The data show that whereas reproductive decline is linked to increasing risks of mortality in chimpanzees, human reproductive senescence precedes somatic senescence. Moreover under traditional conditions, most human males undergo reproductive cessation at the same time as their wives. We then present evidence that after ceasing to reproduce, both men and women provide net economic transfers to children and grandchildren. Given this pattern of economic productivity, delays in menopause would produce net economic deficits within families.

The goals of direct paternal care among a South Amerindian population

Human males are remarkable among mammals in the level of investment they provide to their wives and children. However, there has been debate as to the degree to which men actually invest and through which fitness pathways the benefits of familial investment are realized. Much of the previous research exploring these issues has focused on mens roles as providers, but few have explored correlates of mens direct parental care. Although this is reasonable given mens parental emphasis on provisioning, the providing of direct care is more straightforward with a clear provider and recipient and little ambiguity as to the care-givers intent. Here, we explore contextual correlates of mens direct care among the Tsimane of Bolivia to determine the extent to which such care is patterned to enhance its effectiveness in increasing child wellbeing and the efficient functioning of the family. We also explore whether Tsimane fathers provide care in ways that enhance the positive effect it has on the wifes perception of the care provider. Overall, we find that Tsimane men appear responsive to the needs of children and the family, but show that there is little evidence that men respond to factors expected to increase the impact that mens care has on their reputations with their wives.

Inclusive fitness and differential productivity across the life course determine intergenerational transfers in a small-scale human society

Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamiltons theory of inclusive fitness, we predict that the interaction of biological kinship with the age-schedule of resource production should be a key driver of intergenerational transfers. In the empirical case of Tsimane’ forager–horticulturalists in Bolivian Amazonia, we provide a detailed characterization of net transfers of food according to age, sex, kinship and the net need of donors and recipients. We show that parents, grandparents and siblings provide significant net downward transfers of food across generations. We demonstrate that the extent of provisioning responds facultatively to variation in the productivity and demographic composition of families, as predicted by the theory. We hypothesize that the motivation to provide these critical transfers is a fundamental force that binds together human nuclear and extended families. The ubiquity of three-generational families in human societies may thus be a direct reflection of fundamental evolutionary constraints on an organisms life-history and social organization.

Are men really that bad as fathers? The role of men's investments

Abstract Human pair‐bonding and paternal involvement have long been attributed to the need for biparental rearing of altricial offspring with extended periods of dependency. More recently, researchers have focused on the fertility benefits that pair‐bonding offers men and have re‐conceptualized paternal care as a stratagem designed to curry favor with the recipient childrens mother. These models, however, fail to explain a number of puzzling empirical findings, namely the lack of a significant and robust effect of father‐presence cross‐culturally, despite what appears to be true paternal involvement. I argue that the record is better explained by conceptualizing reproduction within unions as a joint venture, in which mens contributions are not simply lumped onto womens invariant levels of parental investment, but one in which mens involvement allows wives to reduce their own allocations to parental investment and increase those to fertility (fertility model), thereby maximizing the production of the union, not simply child survivorship.

Spousal violence and paternal disinvestment among Tsimane' forager-horticulturalists

We develop and test a conceptual model of factors influencing the likelihood of physical wife abuse. The paternal disinvestment model emphasizes that spousal conflict over resource use results from mens attempts to increase individual fitness at a cost to the family (e.g., through pursuit of extramarital affairs). We propose that men use violence to control womens responses to the diversion of resources away from the family: to quell womens objections to male disinvestment, maintain womens parental investment, and to dissuade women from pursuing relationships with other men.

Polygyny among the Tsimane of Bolivia: an improved method for testing the polygyny -fertility hypothesis

The polygyny–fertility hypothesis states that polygyny is associated with reduced fertility for women and is supported by a large body of literature. This finding is important, because theoretical models of polygyny often differentiate systems based on the degree to which women are forced or willingly choose to enter polygynous marriages. The fact that polygyny tends to be associated with reduced fertility has been presented as evidence that polygyny is often less favourable for women, and that women must, therefore, be pressured into accepting such arrangements. Previous studies, however, have been hampered by the non-random assignment of women into monogamous and polygynous unions (i.e. self-selection), as differences between these groups of women might explain some of the effects. Furthermore, the vast majority of such studies focus on sub-Saharan populations. We address these problems in our analysis of womens fertility in polygynous marriages among the Tsimane of Bolivia. We offer a more robust method for assessing the impact of polygynous marriage on reproductive outcomes by testing for intra-individual fertility effects among first wives as they transition from monogamous to polygynous marriage. We report a significant link between polygyny and reduced fertility when including all cases of polygyny; however, this association disappears when testing only for intra-individual effects.

The Impact of Parents and Self-Selection on Child Survival among the Tsimane of Bolivia

The impact of the parental investment provided by a mother or father on the well-being of a child depends on many factors. The effect of fathers is of particular theoretical interest, as there has been considerable debate concerning the importance of fathers in the evolution of our species and of our reproductive strategies involving long-term pair bonds and biparental care. A common strategy for investigating the impact that parents have on child outcomes is to compare children raised in households without a mother or father to those raised in households with both parents. There is question, however, as to what degree any such effects are simply the result of covarying mortality hazards within families or through time and not necessarily a direct impact of parental absence. Here we explore the issue of self-selection in our investigation of the effects of fathers and mothers on offspring survival among the Tsimane, a forager-horticultural population of central Bolivia. We find strong associations between mother death and child death, while father death has a lesser although still significant effect. We also show the potential for self-selection in parent-absence studies and the need to control for family effects.