Elizabeth Cashdan

A sensitive period for learning about food

It is proposed here that there is a sensitive period in the first two to three years of life during which humans acquire a basic knowledge of what foods are safe to eat. In support of this, it is shown that willingness to eat a wide variety of foods is greatest between the ages of one and two years, and then declines to low levels by age four. These data also show that children who are introduced to solids unusually late have a narrower diet breadth throughout childhood, perhaps because the duration of the sensitive period has been shortened. By reducing the costs associated with learning, a sensitive period for food learning should be adaptive for any omnivore (including early humans) that remains in the same environment throughout its life.

Territoriality Among Human Foragers: Ecological Models and an Application To Four Bushman Groups

Cost-benefit models derived from evolutionary ecology have led to the general expectation that territoriality will be found where resources are most abundant and predictable. Literature sources for four Bushman groups, however, indicate that the most territorial of these groups are found where resources are sparsest and most variable. This paper has as its aim the extension of the animal models of territoriality to make them more widely applicable to human foragers. The Bushmen control access to territorial resources in ways not found in other animals, and it is argued that these differences in the means of territorial defense may alter the expected relationships between environmental variables and territorial costs and benefits. The seemingly anomalous findings concerning Bushman territoriality are shown to be consistemt with cost-benefit theory only when this and other factors are taken into a account.

Hormones, Sex, and Status in Women

Androgens are often associated with assertive behavior; under what circumstances is this reflected in higher dominance rank? In this study of coresidential college women, androgens (total testosterone, free testosterone, and androstenedione) and estradiol were positively correlated with high self-regard in women (as measured by the degree to which subjects over-ranked themselves in a peer-ranking task) and with infrequent smiling, a behavior that has been associated with dominance in previous studies. Androgens and estradiol were also positively correlated with number of sexual partners. The behaviors engendered by these hormones are often positively correlated with high dominance rank, at least in males. In this population, however, high rank (as judged by peer assessments) was negatively correlated with androgens, particularly androstenedione, and showed a negative trend with estradiol as well. One possible interpretation of these findings is suggested by an evolutionary perspective that sees different routes to status among women who compete for resources directly and women who obtain resources through investing males.

Smiles, speech, and body posture: How women and men display sociometric status and power

This study found that power and status have different effects on nonverbal behavior. Participants lived together for a term in ten member groups (50 women, 29 men) and rated their housemates on characteristics related to power (toughness and leadership) and sociometric status (popularity and being well-known). Smiling, arm and leg position, and total talking time were recorded in group discussions, one with housemates only and one with strangers included. Power, but not sociometric status, was associated with open-body postures in women and with frequency of talking in women and men. Smiling was unrelated to power and was positively correlated with sociometric status. Male body posture was more open, but women and men did not differ in frequency of talking or smiling.

Adaptiveness of food learning and food aversions in children

This paper uses an evolutionary perspective to explain features of food learning in human children. Data from Western parents indicate that (1) children are least picky about foods when they are between one and two years of age, (2) vegetables are frequently refused by children, and (3) children have a tendency to eat foods one at a time rather than mixed together. Adaptive explanations for these patterns are suggested, together with supporting evidence from studies of the ontogeny of human and non-human primate diet choice. The following arguments are made: (1) age difference in receptiveness to new foods is consistent with the existence of a sensitive period for learning about food; (2) since leaves and other non-fruit plant parts often contain toxic secondary compounds and young animals are less able to detoxify these chemicals than are adults, an initial dislike of vegetables may function to protect young children against the risk of poisoning; (3) a preference for easily identifiable foods eaten separately may be an evolved preference that aids in identification of the food and the consequences of eating it.

Women's mating strategies

What does a woman want? The traditional evolutionists answer to Freuds famous query is that a womans extensive investment in each of her children implies that she can maximize her fitness by restricting her sexual activity to one, or at most, a few high‐quality males. Because acquiring resources for her offspring is of paramount importance, a woman will try to attract wealthy, high‐status men who are willing and able to help her. She must be coy and choosy, limiting her attentions to men who are worthy of her and emphasizing her chastity so as not to threaten the paternity confidence of her mate.

Attracting mates: Effects of paternal investment on mate attraction strategies☆

Abstract It is proposed here that mate-attraction strategies among females and among males vary facultatively with expectations about paternal investment. The following four hypotheses are argued and tested: 1. Females who expect to find investing mates will be more likely than other females to emphasize their need for investment by suppressing their resources and appearance of competence. 2. Females who expect to find investing mates will try to attract them by acting chaste and emphasizing their fidelity, while females who expect non-investing mates will flaunt their sexuality in order to get pre-reproductive investment from as many males as possible. 3. Males who think it is appropriate to invest heavily in offspring will be more likely than other males to attract mates by emphasizing their ability and willingness to invest. 4. Investing males will be more likely than non-investing males to emphasize chastity and fidelity, whereas non-investing males will flaunt their sexuality and sexual attractiveness to females. These hypotheses were evaluated among undergraduates by administering questionnaires measuring (a) attitudes toward paternal investment and (b) reported tactics used to attract mates. Hypotheses 2–4 were supported by the data, while hypothesis 1 received only partial support. The mixed results for hypothesis 1 indicate that self-deprecating acts and deferential acts may be signaling different things.

Waist‐to‐Hip Ratio across Cultures: Trade‐Offs between Androgen‐ and Estrogen‐Dependent Traits

A gynoid pattern of fat distribution, with small waist and large hips (low waist‐to‐hip ratio, or WHR) holds significant fitness benefits for women: women with a low WHR of about 0.7 are more fecund, are less prone to chronic disease, and (in most cultures) are considered more attractive. Why, then, do nearly all women have a WHR higher than this putative optimum? Is the marked variation in this trait adaptive? This paper first documents the conundrum by showing that female WHR, especially in non‐Western populations, is higher than the putative optimum even among samples that are young, lean, and dependent on traditional diets. The paper then proposes compensating benefits to a high WHR that can explain both its prevalence and variation in the trait. The evidence indicates that the hormonal profile associated with high WHR (high androgen and cortisol levels, low estrogens) favors success in resource competition, particularly under stressful and difficult circumstances, even though this carries fitness costs in fecundity and health. Adrenal androgens, in particular, may play an important role in enabling women to respond to stressful challenges.

Pathogen Prevalence, Group Bias, and Collectivism in the Standard Cross-Cultural Sample

It has been argued that people in areas with high pathogen loads will be more likely to avoid outsiders, to be biased in favor of in-groups, and to hold collectivist and conformist values. Cross-national studies have supported these predictions. In this paper we provide new pathogen codes for the 186 cultures of the Standard Cross-Cultural Sample and use them, together with existing pathogen and ethnographic data, to try to replicate these cross-national findings. In support of the theory, we found that cultures in high pathogen areas were more likely to socialize children toward collectivist values (obedience rather than self-reliance). There was some evidence that pathogens were associated with reduced adult dispersal. However, we found no evidence of an association between pathogens and our measures of group bias (in-group loyalty and xenophobia) or intergroup contact.

Trade and Its Origins On the Botletli River, Botswana

This paper discusses the causes of trade and evaluates the roles played by habitat diversity, mobility, and competition. Ethnographic and ethnohistorical evidence from the Botletli River, Botswana, is used to evaluate some general arguments. The Botletli trade is shown to be based on locational advantages, due to the habitat diversity of the region, and on other comparative advantages arising from differential access to important resources. These factors appear to have become important with increases in population density, which increased the effective habitat diversity of the region and created competition for a limited zone of valuable land.