Eckart Voland

The Comparative Method in Anthropology [and Comments and Reply]

Cross-cultural comparison is a common method of testing hypotheses regarding the co-evolution of elements of cultures or of the adaptiveness of a cultural practice to some aspect of the environment. It has long been recognized, however, that cultures are not independent but rather may share many cultural elements by virtue of common ancestry and proximity. Attempts to address this issue, known as Galtons problem, range from statistically removing confounding variables to using a standard sample of independent cultures. We show here that when testing any hypothesis of co-evolution one should not attempt to identify independent cultures or to create them statistically. Rather, cross-cultural comparative studies must be based upon the identification of independent events of cultural change. Once this principle is applied, it becomes apparent that it is in fact groups of closely related cultures that are potentially the most informative for testing cross-cultural hypotheses. Constructing phylogenies of cultures and placing upon them independent instances of cultural elements arising or changing is an essential part of this task.

Differential reproductive success within the Krummhörn population (Germany, 18th and 19th centuries)

SummaryOn the basis of a family reconstitution study (Krummhörn, Germany, 18th und 19th centuries) it is shown how in one marriage cohort (1720–1750), family land ownership correlates with systematic fitness differentials. Farmers have a greater long-term fitness, on the average, than members of non-peasant population, and farmers possessing better than average wealth achieve a greater long-term fitness than farmers with medium-sized or small landholdings. The proximate causes herefore are to be found in both the varying patterns of marital fertility and in the differences in the marital and migration habits of the children from the various social groups. That is why the number of live births or even the number of surviving children is not the best estimate of a persons genetic contribution to the next generation of the local population. This can be shown by using a new algorithm for the assessment of long-term fitness differentials.

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.

Resource competition and reproduction : The relationship between economic and parental strategies in the Krummhörn population (1720-1874).

A family reconstitution study of the Krummhörn population (Ostfriesland, Germany, 1720–1874) reveals that infant mortality and children’s probabilities of marrying or emigrating unmarried are affected by the number of living same-sexed sibs in farmers’ families but not in the families of landless laborers. We interpret these results in terms of a “local resource competition” model in which resource-holding families are obliged to manipulate the reproductive future of their offspring. In contrast, families that lack resources have no need to manipulate their offspring and are more likely to benefit from allowing their offspring to capitalize on whatever opportunities to reproduce present themselves.

Evolutionary biology and psychiatry: The case of anorexia nervosa

Abstract A review of the literature and an analysis of 19 case histories suggest that evolutionary mechanisms such as reproductive suppression, kin selection, and parental manipulation are involved in the development of anorexia nervosa. From this perspective, anorexia nervosa is viewed as—in some cases—an adaptive feature of human reproductive strategies and may be best understood as an emergency strategy that is pursued whenever the sovereign handling of ones own reproductive potential is not possible because of socioecological or ontogenetic constraints.

Human sex-ratio manipulation: Historical data from a german parish

On the basis of demographic data of a parish in Schleswig-Holstein, characterized by a primarily rural economy, the thesis is developed that during the period investigated, i.e. from 1720 to 1869 A.D., the survival chances of newborns were influenced by differential parental investment. The (first-born) daughters of land-owning farmers were most affected by this intervention, i.e. as a result of less well being taken care of. This resulted in sex-linked infant mortality and therefore a manipulation of the sex ratio. The social undesirability of girls or the preference of, and hence the greater investment in boys by these farmers can be explained by two socio-economic factors that appear to determine the reproductive value of the children: (1) inheritance practices favouring male descendants, and (2) the proportion of marriage perspectives for the sons as opposed to the daughters being in favour of the boys, in contrast to other social classes. The classes of the parish without land property revealed a different pattern of demographic features. Here the irrelevance of inheritance conventions and the relatively good chances of marriage for the daughters (especially the relatively high chances of hypergamy for the daughters of the smallholders) in comparison with those of the sons led to partially reversing of social undesirability and sex-linked reproductive value. Indeed, among the non-possessing classes, the survival chances of the boys were the lowest, relative to their sisters, and those of the girls were the highest. This means that, here too, the operation of cost-benefit-oriented parental investment can be assumed to have been present in the society discussed.

Population Increase and Sex-Biased Parental Investment in Humans: Evidence from 18th-and 19th-Century Germany

female undergraduates living on a coeducational campus. Psychoneuroendocrinology 5:245-52. HENRY, L. I96I. Some data on natural fertility. Eugenics Quarterly 8:8I-9I. HOWIE, P. W., AND A. S. MCNEILLY. i982. Effect of breastfeeding patterns on human birth intervals. Journal of Reproduction and Fertility 65:545-57. JAIN, A. K. I969. Fecundability and its relation to age in a sample of Taiwanese women. Population Studies 23:69-85. JARETT, L. R. I984. Psychosocial and biological influences on menstruation: Synchrony, cycle length, and regularity. Psychoneuroendocrinology 9:21i-28. JOHNSON, P. L., J. W. WOOD, K. L. CAMPBELL, AND I. A.

Cost/benefit oriented parental investment by high status families: The Krummhörn case

Abstract Infant and child mortality in 18th and 19th century Krummhorn exhibits a remarkable feature: significantly more daughters than sons of comparably prosperous high status farmers achieve adulthood. We interpret this difference as being the outcome of differential parental care reflecting varying reproductive perspectives and social role expectations, to which sons and daughters from farmer families were exposed. This is verified by sex differences in the childrens probability of marrying and their differing chances of social persistence. Against the background of severely restricted reproductive opportunities and recognizably higher upbringing costs for a son, parental underinvestment in the survival of sons can be best understood as an economically motivated measure in the course of a farmers efforts to concentrate his property and to maintain his familys social status. At the same time, such a scenario also had a biological adaptive value, because it contributed to the intergenerational perpetuation of above average chances of life and reproduction, and hence, to the genetic persistence of the farmer families.

How did the Krummhörn elite males achieve above-average reproductive success?

AbstractThe wealthy elite males of nineteenth-century Krummhörn (Ostfriesland, Germany) achieved an above-average reproductive success. Membership in the elite class was determined from a list of the 300 richest men in the Ostfriesland district compiled by authorities in 1812. The main components establishing the link between cultural success and reproductive success are1.differences in the number of offspring owing to differences both in time spent in fecund marriage (mating success) and in rate of reproduction;2.differences in the probabilities of one’s adult offspring marrying locally vs. emigrating unmarried owing to differential ability to allocate resources that enhance the “social placement” of adult offspring; and3.differences in the probability of total reproductive failure (lineage extinction).n Contrary to what might be expected, infant survivorship was lowest amongst the richest families. We conclude that to a great extent females’ reproductive decisions contribute to the greater reproductive success of the elite males.

Social play behavior of the common marmoset (Callithrix jacchus Erxl., 1777) in captivity

Twenty-one captive marmosets (Callithrix jacchusErxl., 1777) were observed as to the ethology of social play. With the aid of video tape recordings, 38 elements of behavior comprising play episodes were distinguished. The peer group was composed of the nonadult members of the family group, whereby the twin was found to be the preferred partner, as measured by the duration of play. Social play is often accompanied by various communicative signals. Contemporary theoretical concepts of social play were tested on the basis of the results of this study.