Lee Cronk

Adaptation and human behavior : an anthropological perspective

This volume presents state-of-the-art empirical studies working in a paradigm that has become known as human behavioral ecology. The emergence of this approach in anthropology was marked by publication by Aldine in 1979 of an earlier collection of studies edited by Chagnon and Irons entitled Evolutionary Biology and Human Social Behavior: An Anthropological Perspective. During the two decades that have passed since then, this innovative approach has matured and expanded into new areas that are explored here. The book opens with an introductory chapter by Chagnon and Irons tracing the origins of human behavioral ecology and its subsequent development. Subsequent chapters, written by both younger scholars and established researchers, cover a wide range of societies and topics organ-ized into six sections. The first section includes two chapters that provide historical background on the development of human behavioral ecology and com-pare it to two complementary approaches in the study of evolution and human behavior, evolutionary psychology, and dual inheritance theory. The second section includes five studies of mating efforts in a variety of societies from South America and Africa. The third section covers parenting, with five studies on soci-eties from Africa, Asia, and North America. The fourth section breaks somewhat with the tradition in human behavioral ecology by focusing on one particularly problematic issue, the demographic transition, using data from Europe, North America, and Asia. The fifth section includes studies of cooperation and helping behaviors, using data from societies in Micronesia and South America. The sixth and final section consists of a single chapter that places the volume in a broader critical and comparative context. The contributions to this volume demonstrate, with a high degree of theoretical and methodological sophistication--the maturity and freshness of this new paradigm in the study of human behavior. The volume will be of interest to anthropologists and other professions working on the study of cross-cultural human behavior.

Dance reveals symmetry especially in young men

Dance is believed to be important in the courtship of a variety of species, including humans, but nothing is known about what dance reveals about the underlying phenotypic—or genotypic—quality of the dancer. One measure of quality in evolutionary studies is the degree of bodily symmetry (fluctuating asymmetry, FA), because it measures developmental stability. Does dance quality reveal FA to the observer and is the effect stronger for male dancers than female? To answer these questions, we chose a population that has been measured twice for FA since 1996 (ref. 9) in a society (Jamaican) in which dancing is important in the lives of both sexes. Motion-capture cameras created controlled stimuli (in the form of videos) that isolated dance movements from all other aspects of visual appearance (including FA), and the same population evaluated these videos for dancing ability. Here we report that there are strong positive associations between symmetry and dancing ability, and these associations were stronger in men than in women. In addition, women rate dances by symmetrical men relatively more positively than do men, and more-symmetrical men value symmetry in women dancers more than do less-symmetrical men. In summary, dance in Jamaica seems to show evidence of sexual selection and to reveal important information about the dancer.

Explaining Biased Sex Ratios in Human Populations: A Critique of Recent Studies [and Comments and Reply]

DANIELA F. SIEFF is a graduate student in human ecology at the University of California, Davis (Davis, Calif. 956I6, U.S.A.). Born in I965, she received a B.A. from Oxford University in I987 and an M.A. in anthropology and psychology from the University of Michigan in I989. Her research interests are parental-investment strategies and the costs of children in traditional societies. She is currently engaged in a study of the interaction of womens work, polygyny, fertility, and child care among the Dotoga pastoralists of northern Tanzania. The present paper was submitted in final form 30 vi 89.

Preferential parental investment in daughters over sons

Female-biased parental investment is unusual but not unknown in human societies. Relevant explanatory models include Fisher’s principle, the Trivers-Willard model, local mate and resource competition and enhancement, and economic rational actor models. Possible evidence of female-biased parental investment includes sex ratios, mortality rates, parents’ stated preferences for offspring of one sex, and direct and indirect measurements of actual parental behavior. Possible examples of female-biased parental investment include the Mukogodo of Kenya, the Ifalukese of Micronesia, the Cheyenne of North America, the Herero of southern Africa, the Kanjar of south Asia, the Mundugumor of New Guinea, contemporary North America, and historical Germany, Portugal, and the United States.

The application of animal signaling theory to human phenomena: some thoughts and clarifications

Animal signaling theory has recently become popular among anthropologists as a way to study human communication. One aspect of animal signaling theory, often known as costly signaling or handicap theory, has been used particularly often. This article makes four points regarding these developments: (1) signaling theory is broader than existing studies may make it seem; (2) costly signaling theory has roots in the social as well as the biological sciences; (3) not all honest signals are costly and not all costs borne by signalers serve to ensure honesty; and (4) hard-to-fake signals are favored when the interests of broad categories of signalers and receivers conflict but the interests of individual signalers and receivers converge.

Is there a role for culture in human behavioral ecology

Abstract Most research in human behavioral ecology has been acultural, which raises the question of how best to incorporate the concept of culture into this approach. A necessary step in this direction is to pare the culture concept down to its ideational elements, excluding behavior and its material products (Durham 1991; Geertz 1973; Keesing 1974). The cultural and reproductive success hypothesis, though empirically successful (Irons 1993), is not a model for all of culture because of widespread discrepancies between behavior and culture to which it does not call attention. Cultural transmission models are also weakened by such discrepancies, but, more importantly, such models are most relevant to phenomena different from those central to human behavioral ecology. A better way to incorporate culture into human behavioral ecology is to see it as the context of human action and as a tool people use in social manipulation. The study of signal systems is a key to an understanding of social manipulation and to the incorporation of culture into human behavioral ecology. Examples of the manipulation of culture for reproductive benefit include Yanomamo kin term manipulation (Chagnon 1988), incest rules (Thornhill 1990, 1991), and the derogation of sexual competitors (Buss and Dedden 1990). The human behavioral ecological study of social manipulation in cultural contexts needs to be expanded. Two phenomena that might shed light on such manipulation are the Rashomon effect and the audience effect.

Boy or girl: gender preferences from a Darwinian point of view

This article reviews evolutionary biological studies of sex-biased post-natal parental investment that may be relevant to the issue of preconception gender selection. The focus is on tests of the Trivers-Willard hypothesis, which predicts that natural selection has favoured parents that bias investment in favour of the sex with the best reproductive prospects. Because resource abundance and scarcity often have greater effects on male than on female reproductive success, the Trivers-Willard model predicts that natural selection will most often favour parents who favour males when conditions are good and females when conditions are poor. Empirical tests of this hypothesis are mixed in terms of the appropriateness of their methods and their relevance to the model. Tests with more appropriate measures of such key variables as parental investment tend more often to provide support for the hypothesis. The implications of these findings for the issue of preconception gender selection are briefly discussed.

Amounts Spent on Engagement Rings Reflect Aspects of Male and Female Mate Quality

Previous research has shown that the qualities of nuptial gifts among nonhumans and marriage-related property transfers in human societies such as bridewealth and dowry covary with aspects of mate quality. This article explores this issue for another type of marriage-related property transfer: engagement rings. We obtained data on engagement ring costs and other variables through a mail survey sent to recently married individuals living in the American Midwest. This article focuses on survey responses regarding rings that were purchased by men acting alone and using only their own funds who then presented the rings while making surprise proposals of marriage (n = 127). Men marrying younger women spent more on rings, as did men who earned more money and whose fiancées earned more money. These findings suggest that the amounts spent on engagement rings, like bridewealth and dowry payments in other societies, reflect aspects of both male and female mate quality.

FROM TRUE DOROBO TO MUKOGODO MAASAI: CONTESTED ETHNICITY IN KENYA

Between 1925 and 1936, the Mukogodo of Kenya changed from Cushitic-speaking foragers to Maa-speaking pastoralists. This rapid transition took place in the midst of competing views of Mukogodo ethnic identity. To Maa-speakers, Mukogodo were low-status il-torrobo. To British colonialists, Mukogodo were true Dorobo, victims of more powerful agricultural and pastoralist groups. Although British administrators fashioned a set of policies designed to protect Mukogodo from such groups, other British policies inadvertently contributed to the Mukogodo acquisition of Maasai subsistence patterns, language, and culture. Mukogodo themselves strategically used a Dorobo identity to manipulate the British while striving to lose the stigma of the il-torrobo label and achieve acceptance among Maa-speakers as true Maasai. (Mukogodo, Dorobo, Torrobo, Maasai, Samburu, ethnicity, Kenya) ********** Between the mid-1920s and mid-1930s, Mukogodo of Kenya underwent a rapid transition from being Cushitic-speaking hunters, gatherers, and beekeepers to being Maa-speaking pastoralists. (2) This transition is problematic in a number of ways. First, thanks to data on time allocation collected since the 1960s, it can no longer be assumed that a change from foraging to food production will improve a groups standard of living or reduce the workloads of its members (see Hames 1992 for a review). In the Mukogodo case specifically, there is no convincing evidence of an increase in standard of living since their acquisition of livestock (Cronk 1989b). Second, other hunter-gatherers in East Africa in superficially similar situations have remained hunter-gatherers despite contact with pastoralists (e.g., Hadza; see Kaare and Woodburn 1999), and Mukogodo themselves had had contact with pastoralists for centuries before the transition without themselves becoming pastoralists. Third, it cannot be taken for granted that even if a group does change its subsistence strategy it will also necessarily undergo the sort of wholesale cultural shift experienced by Mukogodo. Other groups in East Africa have made similar changes in subsistence while still keeping their own languages and other aspects of their own cultures (e.g., Okiek; Huntingford 1928, 1929, 1931, 1942, 1951, 1954, 1955; Blackburn 1976, 1982; Kratz 1981, 1994, 1999). Elsewhere (Cronk 1989a, 1989b) I have analyzed the Mukogodo transition in behavioral ecological terms, suggesting that for individual Mukogodo men the adoption of pastoralism represented a response to a rapidly changing social environment in which they either obtained livestock or failed to marry. I have also examined some of the consequences of the Mukogodo transition to pastoralism, including their low position in a regional hierarchy of wealth and ethnic status (Cronk 1989c, 1990, 1991c). This article explores the change from a different but complementary angle, focusing more on the external factors that changed their social environment. An examination of the broader historical and political context reveals that the Mukogodo transition occurred as Mukogodo attempted to manipulate the attitudes and behaviors of both British colonialists and Maasai pastoralists, two groups with competing and strikingly different views of Mukogodo ethnicity. THE EMERGENCE OF A MUKOGODO ETHNICITY Mukogodo live on the northeastern edge of the Laikipia Plateau in and around the Mukogodo Hills, which are covered with a dry forest dominated by cedar and wild olive trees (Mukogodo Division, Laikipia District, Rift Valley Province, Kenya). The origins of the Mukogodo people are obscure, but linguistic evidence suggests that they may have roots among the original Khoisan-speaking hunters and gatherers of East Africa (Ehret 1974:88). Until recent decades, however, they spoke not a Khoisan language, but rather an Eastern Cushitic one called Yaaku (Heine 1974-75; see also Brenzinger 1992 and Brenzinger, Heine, and Heine 1994). …

Lactase persistence and lipid pathway selection in the Maasai.

The Maasai are a pastoral people in Kenya and Tanzania, whose traditional diet of milk, blood and meat is rich in lactose, fat and cholesterol. In spite of this, they have low levels of blood cholesterol, and seldom suffer from gallstones or cardiac diseases. Field studies in the 1970s suggested that the Maasai have a genetic adaptation for cholesterol homeostasis. Analysis of HapMap 3 data using Fixation Index (Fst) and two metrics of haplotype diversity: the integrated Haplotype Score (iHS) and the Cross Population Extended Haplotype Homozygosity (XP-EHH), identified genomic regions and single nucleotide polymorphisms (SNPs) as strong candidates for recent selection for lactase persistence and cholesterol regulation in 143–156 founder individuals from the Maasai population in Kinyawa, Kenya (MKK). The non-synonmous SNP with the highest genome-wide Fst was the TC polymorphism at rs2241883 in Fatty Acid Binding Protein 1(FABP1), known to reduce low density lipoprotein and tri-glyceride levels in Europeans. The strongest signal identified by all three metrics was a 1.7 Mb region on Chr2q21. This region contains the genes LCT (Lactase) and MCM6 (Minichromosome Maintenance Complex Component) involved in lactase persistence, and the gene Rab3GAP1 (Rab3 GTPase-activating Protein Catalytic Subunit), which contains polymorphisms associated with total cholesterol levels in a genome-wide association study of >100,000 individuals of European ancestry. Sanger sequencing of DNA from six MKK samples showed that the GC-14010 polymorphism in the MCM6 gene, known to be associated with lactase persistence in Africans, is segregating in MKK at high frequency (∼58%). The Cytochrome P450 Family 3 Subfamily A (CYP3A) cluster of genes, involved in cholesterol metabolism, was identified by Fst and iHS as candidate loci under selection. Overall, our study identified several specific genomic regions under selection in the Maasai which contain polymorphisms in genes associated with lactase persistence and cholesterol regulation.