Effect of household structure on female reproductive strategies in a Caribbean village

Household structure may have strong effects on reproduction. This study uses household demographic data for 59 women in a Caribbean village to test evolutionary hypotheses concerning variation in reproductive strategies. Father-absence during childhood, current household composition, and household economic status are predicted to influence age at first birth, number of mates, reproductive success, and pair-bond stability. Criterion variables did not associate in a manner indicative of r- and K-strategies. Father-absence in early childhood had little influence on subsequent reproduction. Household wealth and alloparenting were positively associated with age at first birth. Alloparenting was negatively associated with reproductive success. Women in long-term conjugal unions had higher reproductive success than did single women. Number of adult male kin resident in the household was negatively associated with women’s number of mates. This research was funded by NSF grants (BNS 8920569 and SBR 9205373) to Mark Flinn and an Earthwatch Center for Field Research grant to Mark Flinn, Robert Quinlan, and Marsha Quinlan. Robert Quinlan is currently an assistant researcher at the Research Corporation of the University of Hawai’i. He has a Ph.D. in Anthropology from the University of Missouri. His research interests include human evolutionary ecology, household demography, and biomedical anthropology.     

Kinship,Family, and Gender Effects in the Ultimatum Game

Kinship and reciprocity are two main predictors of altruism. The ultimatum game has been used to study altruism in many small-scale societies. We used the ultimatum game to examine effects of individuals’ family and kin relations on altruistic behavior in a kin-based horticultural community in rural Dominica. Results show sex-specific effects of kin on ultimatum game play. Average coefficient of relatedness to the village was negatively associated with women’s ultimatum game proposals and had little effect on men’s proposals. Number of brothers in the village was positively associated with men’s ultimatum game proposals and negatively associated with women’s proposals. Similarly, presence of father in the village was associated with higher proposals by men and lower proposals by women. We interpret the effect of brothers on men’s proposals as a consequence of local competition among brothers. We speculate that daughter-biased parental care in this community creates a sense of entitlement among women with brothers, which may explain the inverse relation between number of brothers and women’s ultimatum game proposals. The pattern of results may be consistent with how matrifocality affects cultural models of fairness differently along gender and family lines.     

Age-related changes of bone mineral density in human calcaneus, talus, and scaphoid bone

To examine whether the bone mineral density (BMD) decreases uniformly with aging in any spongy bones, the authors investigated age-related changes of BMD in the calcaneus, talus, and scaphoid bone. After the ordinary dissection by medical students was finished, calcanei, tali, and scaphoid bones were resected from the subjects, and BMDs were measured by dual-energy X-ray absorptiometry. Their BMDs seemed to decrease gradually with aging in the calcanei, tali, and scaphoid bones. It was found that there were statistically significant relationships between age and BMD in the men’s and women’s scaphoid bones, women’s tali, and women’s calcanei, but not in the men’s tali and calcanei. It should be noted that there were significant relationships between age and BMD in both men’s and women’s scaphoid bones. In regard to relationship in BMD between the bones of the upper and lower limbs in individuals, it was found that the relationship between the calcaneus and talus was higher than that between the calcaneus and scaphoid bone. This suggests that there is a higher relationship in BMD between the two tarsal bones compared with that between the tarsal and carpal bones.     

High accumulations of calcium and phosphorus in women’s pubic symphysis

To elucidate compositional changes of the pubic symphysis (PS) by aging, elements of pubic symphyses (PSs) removed from 26 cadavers were determined by inductively coupled plasma atomic-emission spectrometry. It was found that the relative contents (RCs) of calcium and phosphorus in women’s PSs were about three-and five-fold amounts as compared with those in men’s PSs, respectively. In contrast, the RCs of sulfur, magnesium, sodium, and iron in women’s PSs were somewhat lower than those in men’s PSs. The accumulations of calcium (Ca) and phosphorus (P) in women’s PSs occurred mainly beyond the age of 70-yr-old, but did not occur in men’s PSs.     

Willingness to engage in casual sex

Sexually dimorphic mate selection strategies were examined in 200 university students reporting their willingness to engage in casual sexual encounters with hypothetical individuals of the opposite sex. Using a questionnaire format, the possibility of forming a long-term relationship was manipulated, while risk of disease, pregnancy, and detection was eliminated across all conditions. In addition, potential partners varied in level of attractiveness, and in personality and behavioral characteristics. As expected, men reported a greater anticipated willingness to engage in sexual intercourse across all conditions compared with women. The possibility of forming a long-term relationship elevated women’s, but not men’s, willingness for sexual intercourse. While a potential partner’s attractiveness had a significant positive overall effect on responses, reducing their relative attractiveness had a greater negative impact on men’s responses. Reference to the parental qualities of a potential partner significantly increased women’s, but not men’s, anticipated willingness for sexual intercourse. Describing a hypothetical partner as non-aggressive (safe) marginally increased women’s willingness (p<.09) and did not affect men’s responses. The wording of items relevant to this condition may have resulted in the potential partner sounding "wimpy" rather than nonaggressive, and this may have reduced the expected effect of this manipulation. The possibility that women may trade off personality and behavioral characteristics with attractiveness to a greater degree than men when assessing potential mates is considered.     

How Willing Are You to Accept Sexual Requests from Slightly Unattractive to Exceptionally Attractive Imagined Requestors?

In their classic study of differences in mating strategies, Clark and Hatfield (1989, Journal of Psychology and Human Sexuality, 2, 39–54) found that men and women demonstrated a striking difference in interest in casual sex. The current study examined the role of an imagined requestor’s physical attractiveness (slightly unattractive, moderately attractive, and exceptionally attractive) on men’s and women’s willingness to accept three different requests (go out, come to apartment, go to bed) as reflected in answers to a questionnaire. We tested two hypotheses with a sample of 427 men and 443 women from three countries. Hypothesis 1 states that men, relative to women, will demonstrate a greater willingness to accept the “come to apartment” and “go to bed” requests but not the “go out” request for all three levels of requestor attractiveness. This hypothesis reflects Clark and Hatfield’s main findings. Hypothesis 2 states that the physical attractiveness of a potential partner will have a greater effect on women’s than on men’s willingness to accept all three requests, and particularly for the explicit request for casual sex. The results partially supported Hypothesis 1 and fully supported Hypothesis 2. The discussion highlights limitations of the current research and presents directions for future research.     

Relative digit lengths predict men’s behavior and attractiveness during social interactions with women

Recent evidence suggests that the ratio of the lengths of the second and fourth fingers (2D:4D) may reflect degree of prenatal androgen exposure in humans. In the present study, we tested the hypotheses that 2D:4D would be associated with ratings of men’s attractiveness and with levels of behavioral displays during social interactions with potential mates. Our results confirm that male 2D:4D was significantly negatively correlated with women’s ratings of men’s physical attractiveness and levels of courtship-like behavior during a brief conversation. These findings provide novel evidence for the organizational effects of hormones on human male attractiveness and social behavior. This work was supported by a Hind’s Fund Research Grant from the Committee on Evolutionary Biology at the University of Chicago to J.R.R. and by NIH grants R01-MH62577 and K02-MH63097 to D.M. James Roney, Ph.D., is now an assistant professor of psychology at the University of California, Santa Barbara. His research interests are in human evolutionary psychology and behavioral endocrinology. Dario Maestripieri, Ph.D., is an associate professor of Human Development at the University of Chicago. He has broad research interests in behavior, development, and evolution.     

Girl helpers and time allocation of nursing women among the Toba of Argentina

In this paper we outline the activities of young girls in a Toba community of northern Argentina and examine the effect of girl helpers on time allocation of nursing women. Activity budgets were obtained for 41 girls aged 3 to 15 using spot observations. Girls spent substantial portions of observations engaged in helping behaviors. Individual values varied with age, anthropometric characteristics, and birth order. Activity budgets of 21 nursing women were obtained through focal observation sessions. Women living in households with girls aged 7 to 15 allocated 17% less time to domestic work and 9% more time to socializing during afternoon observation sessions. For nursing women in this community, direct childcare (provided by the infant’s own mother) seemed to be a priority. Living with a girl helper did not have any measurable effect on the frequency or duration of nursing, or on the time that women spent caring for their infants. Based on these findings, hypotheses are outlined for future work on the effect of girl helpers on women’s fertility. Research for this project was funded by the Nestlé Foundation, the Harvard Anthropology Goelet Fund, and the Harvard College Research Program. Eduardo Fernandez-Duque commented on an early draft of this paper. Riley Bove (A.B., Harvard, 1998) is a research associate in the Department of Anthropology at Harvard University with research interests in intergenerational female networks and polygyny as a social mediator of women’s health (esp. urban, African). Claudia Valeggia (Ph.D., U.C. Davis, 1996) is a postdoctoral fellow in the Department of Anthropology at Harvard University with research interests in reproductive ecology and ethnopediatry. Peter Ellison (Ph.D., Harvard, 1983) is a professor of anthropology and director of the Reproductive Ecology Laboratory at Harvard University. He is the author of On Fertile Ground: Ecology, Evolution and Human Reproduction (Harvard University Press, 2001).     

Cyclic variation in women’s preferences for masculine traits

Women’s preferences for several male traits, including voices, change over the menstrual cycle, but the proximate causes of these changes are unknown. This paper explores relationships between levels of estradiol, progesterone, luteinizing hormone, follicle stimulating hormone, prolactin, and testosterone (estimated using menstrual cycle information) and women’s preferences for male vocal masculinity in normally cycling and hormonally contracepting heterosexual females. Preferences for vocal masculinity decreased with predicted progesterone levels and increased with predicted prolactin levels in normally cycling—but not hormonally contracepting—women. Adaptive explanations for menstrual variation in women’s preferences for masculine traits are discussed and evaluated in light of these findings.     

Male-female differences in effects of parental absence on glucocorticoid stress response

This study examines the family environments and hormone profiles of 316 individuals aged 2 months-58 years residing in a rural village on the east coast of Dominica, a former British colony in the West Indies. Fieldwork was conducted over an eight-year period (1988–1995). Research methods and techniques include radioimmunoassay of cortisol and testosterone from saliva samples (N=22,340), residence histories, behavioral observations of family interactions, extensive ethnographic interview and participant observation, psychological questionnaires, and medical examinations. Analyses of data indicate complex, sex-specific effects of family environment on endocrine function. Male endocrine profiles exhibit greater sensitivity to presence of father than do female endocrine profiles. Father-absent males tend to have (a) low cortisol levels during infancy, (b) high or abnormal cortisol profiles during childhood and adolescence, and (c) high cortisol and low testosterone levels during adulthood compared with those of males raised with a resident father. These results indicate that early family environment has significant effects on endocrine response throughout male life histories. Mark V. Flinn is an Associate Professor of Anthropology at the University of Missouri, Columbia. He studies family relationships, endocrine stress response, and child health from a mix of evolutionary and developmental psychology perspectives. Robert J. Quinlan is a graduate student in the Department of Anthropology at the University of Missouri, Columbia. His interests include time allocation, family relationships, and medical anthropology. He is planning a long-term ethnographic study of cross-cousin marriage among the E’nyepa of Venezuela. Mark T. Turner is a graduate student in the Department of Anthropology at Northwestern University. He studies covariance of mother and infant hormone and immune function in naturalistic settings using assays from saliva and breast milk samples and ethnographic observations. Seamus A. Decker is a graduate student in the Department of Anthropology at Emory University. He has studied social factors associated with daily variations of salivary cortisol and testosterone levels among males in a Caribbean village. He is currently investigating levels of stress in rural and urban populations in Botswana. Barry G. England is an Associate Professor of Pathology and director of the ligand assay laboratories of the University of Michigan Hospitals. His primary interests concern reproductive endocrinology.     

Invasion fitness,inclusive fitness,and reproductive numbers in heterogeneous populations

How should fitness be measured to determine which phenotype or “strategy” is uninvadable when evolution occurs in a group‐structured population subject to local demographic and environmental heterogeneity? Several fitness measures, such as basic reproductive number, lifetime dispersal success of a local lineage, or inclusive fitness have been proposed to address this question, but the relationships between them and their generality remains unclear. Here, we ascertain uninvadability (all mutant strategies always go extinct) in terms of the asymptotic per capita number of mutant copies produced by a mutant lineage arising as a single copy in a resident population (“invasion fitness”). We show that from invasion fitness uninvadability is equivalently characterized by at least three conceptually distinct fitness measures: (i) lineage fitness, giving the average individual fitness of a randomly sampled mutant lineage member; (ii) inclusive fitness, giving a reproductive value weighted average of the direct fitness costs and relatedness weighted indirect fitness benefits accruing to a randomly sampled mutant lineage member; and (iii) basic reproductive number (and variations thereof) giving lifetime success of a lineage in a single group, and which is an invasion fitness proxy. Our analysis connects approaches that have been deemed different, generalizes the exact version of inclusive fitness to class‐structured populations, and provides a biological interpretation of natural selection on a mutant allele under arbitrary strength of selection.     

Rational Love,Relational Medicine: Psychiatry and the Accumulation of Precarious Kinship

In north Indian psychiatry, clinical attentions to women’s symptoms often involve scrutiny of emotions related to marriage and its breakdown. In pharmaceutically oriented practice, relations are used to evaluate biologies, and drugs produce the truth about relations at the same time that they produce the truth about bodies. In the process, clinical practice often involves unmaking relations, generating loss, in certain instances, as a dire result. In this, a particular kind of clinical knowing emerges, engaging broad cultural and historical connections between love and madness more than definitions of right and wrong unions. In asking how disciplinary and relational modes of biomedicine converge, I argue that in north Indian psychiatry’s attentions to women, rather than enforcing normative configurations of “the family,” biomedicine grapples with the gendered fallout of kinship.     

Age-Dependent changes of mineral contents in men and women’s calcanei

To elucidate age-related change of mineral contents in human bones, the mineral content and density of human calcanei were determined by inductively coupled plasma atomic emission spectrometry and dual-energy X-ray absorptiometry. Calcanei were removed from 27 subjects (17 men and 10 women) who died in the age range from 40–98 yr old. Both the inductively coupled plasma emission spectrometry and dual-energy X-ray absorptiometry indicated that there were agedependent decreases of the mineral contents and density in the men’s calcaneus in the age range from 40–98 yr, but not in the women’s calcaneus in the age range from 42–87 yr. It was also found that the calcanean masses of the men and women remained constant within the same age range until 98 yr.     

Modes of cooperation during territorial defense by African lions

Cooperation during territorial defense allows social groups of African lions to defend access to resources necessary for individual reproductive success. Some forms of cooperation will be dependent upon cognition: reciprocity places greater cognitive demands on participants than does kinship or mutualism. Lions have well-developed cognitive abilities that enable individuals to recognize and interact with others in ways that seem to enhance their inclusive fitness. Male lions appear to cooperate unconditionally, consistently responding to roaring intruders regardless of their male companions’ kinship or behavior. Female lions, however, do keep track of the past behavior of their female companions, apparently using the reliability of a companion as one means of assessing the risks posed by approaching intruders. Some “laggard” females may exploit the cooperative tendencies of “leaders” during territorial encounters. Although leader females clearly recognize laggards as such, the costs of tolerating laggards may be less than the benefits leaders gain through territorial defense behavior. Thus, although lions clearly have the cognitive ability to base cooperation on reciprocity, territorial defense cooperation appears instead to be based primarily on mutual benefits to participants for both male and female lions.     

There is no fitness but fitness,and the lineage is its bearer

Inclusive fitness has been the cornerstone of social evolution theory for more than a half-century and has matured as a mathematical theory in the past 20 years. Yet surprisingly for a theory so central to an entire field, some of its connections to evolutionary theory more broadly remain contentious or underappreciated. In this paper, we aim to emphasize the connection between inclusive fitness and modern evolutionary theory through the following fact: inclusive fitness is simply classical Darwinian fitness, averaged over social, environmental and demographic states that members of a gene lineage experience. Therefore, inclusive fitness is neither a generalization of classical fitness, nor does it belong exclusively to the individual. Rather, the lineage perspective emphasizes that evolutionary success is determined by the effect of selection on all biological and environmental contexts that a lineage may experience. We argue that this understanding of inclusive fitness based on gene lineages provides the most illuminating and accurate picture and avoids pitfalls in interpretation and empirical applications of inclusive fitness theory.     

Age-independent constancy of mineral contents in human vertebra and auditory ossicle

To elucidate age-related changes of mineral contents in human bones, element contents of human vertebrae and auditory ossicles were determined by inductively coupled plasma atomic-emission spectrometry. The cervical, thoracic, and lumbar vertebrae were removed from 12 vertebral columns. The mallei of auditory ossicle were removed from 27 cadavers. It was found that average relative contents (RCs) of calcium and phosphorus in cervical, thoracic, and lumbar vertebrae remained almost constant within ages ranging from 46 to 99 y. In addition, it was found that the RCs of calcium and phosphorus in men’s and women’s mallei remained constant within ages ranging from 40 to 98 yr. These results support the view that there is no significant agedependent change of mineral contents in human bones.     

Reproductive skew and individual strategies: infanticide or cooperation?

Infanticide in species with shared reproduction may indicate attempts to control the degree of skew within groups. Alternatively, individuals that have done poorly in reproduction could use infanticide for hastening the next breeding attempt. Many factors influence the individual’s decision over whether it is best to cooperate or engage in destruction. We present a qualitative model incorporating kinship among adults and progeny, social status, group size and seasonality to predict behavioural options for individuals of diverse backgrounds. The social system used for the model was that of the guira cuckoo (Guira guira), a Neotropical bird that breeds communally. We suggest communal breeders utilise the best available predictors for enhancing seasonal reproductive success, with favourable consequences for lifetime inclusive fitness. Predictors rely upon parameters that change over time, including the individual’s assessment of present and future possibilities. The model produces predictions that may be tested through field observations and molecular analyses for species with similar social dynamics.     

A reexamination of Gilligan’s analysis of the female moral system

Gilligan’s (1982) refinement of Kohlberg’s theory on moral development operates on two theses: (1) females, more so than males, reach moral decisions based on the personalities of the relevant individuals; and (2) female behaviors stemming from moral decisions are based upon “care” and “responsibility for others.” This article accepts the first thesis but argues that the second is incorrect. That is, self-interest—i.e., aiding “blood” kin and/or carefully monitoring reciprocity—rather than “altruism” is argued to be the operant dynamic in forging distaff morality and resultant behavior. Six empirical examples are presented as contraindicative of Gilligan’s second thesis. Finally, it is suggested that selection for the psychological traits of independence and the mastery of subtle social chess yielded ancestral females who had more descendants—us—than did females with alternative profiles. Nancy S. Coney is a professor at Western Illinois University and is interested in both clinical and nonclinical aspects of women’s psychology. Wade C. Mackey is interested in biocultural anthropology and has authored two books on fathering:Fathering Behaviors (Plenum, 1995) andThe American Father (Plenum, 1996).     

Partner Status Influences Women’s Interest in the Opposite Sex

Previous research has demonstrated that hormones, relationship goals, and social context influence interest in the opposite sex. It has not been previously reported, however, whether having a current sexual partner also influences interest in members of the opposite sex. To test this, we obtained explicit and implicit measures of interest by measuring men’s and women’s subjective ratings and response times while they evaluated photos of opposite-sex faces. Fifty-nine men and 56 women rated 510 photos of opposite-sex faces for realism, masculinity, attractiveness, or affect. We found that these subjective ratings were not influenced by partner status in either men or women. However, women who did not report having a current sexual partner spent more time evaluating the photos than women who did have partners, demonstrating greater interest in the photos. Sexual partner status did not predict men’s response times. These findings may reveal that relationship commitment in women suppresses interest in alternative partners.

Age-related changes of element contents in the human meniscus

The relative contents (RCs) of elements in the human menisci from 23 subjects in the age range between 65 and 93 yr were analyzed by inductively coupled plasma atomic emission spectrometry. The RCs of sulfur, calcium, and phosphorus in menisci increased progressively until the 80s, being the highest in the 80s, and thereafter decreased. The RCs of magnesium in menisci increased progressively until the 90s. Regarding the medial and lateral menisci, higher RCs of magnesium and iron, and a lower RC of phosphorus were found in lateral menisci in comparison with those in medial menisci. There were sexual differences in the RCs of calcium and phosphorus of medial and lateral menisci. The RCs of calcium and phosphorus were about 50% higher in women’s menisci than in men’s. Histological examinations showed that structureless mucoid masses were observed in the menisci, with very high RCs of calcium and phosphorus being detected.