Marital Status and Infanticide
This entry concerns the relationship between an individual’s marital status (e.g., unmarried, married, widowed) and the intentional killing of infant offspring. While infanticide (the killing of children up to 2 years of age) is sometimes treated separately from neonaticide (the killing of newborns within the first 24 h of birth), both phenomena are considered.
Contemporary evolutionary approaches to infanticide emphasize a life history perspective. Life history theory assumes that individuals will exhibit behaviors that, on average and subject to constraints, maximize their lifetime reproductive success and that of their progeny while minimizing energetic costs (Clutton-Brock 1991; Stearns 1992). Life history theory emphasizes tradeoffs; for instance, between quality and quantity of offspring, between current and future reproduction, or between somatic maintenance and reproduction. Parental investment theory is a subset of life history theory that considers how parents optimally allocate resources toward offspring (Trivers 1972). Scholars have applied this lens to human parental investment by examining modulation of investment in relation to socioecological factors and offspring quality (Hrdy 1992; Lawson and Mulder 2016; Minocher and Sommer 2016).
Infanticide, when committed by a parent, constitutes a complete termination of parental investment. A life history approach aims to identify and explain the conditions under which attenuation or termination of parental investment is expected to yield a net fitness benefit to the parent. From this perspective, marital status is expected to influence investment decisions whenever marriage influences the relative costs and benefits of reproduction and investment behavior (for instance, when marriage entails significant material and social support or grants social legitimacy to both parents and children).
Historical accounts suggest that infanticide is recurrent across time and space. They also suggest that consistent demographic similarities exist among individuals who commit infanticide. Resnick’s (1970) review of worldwide infanticide records from the seventeenth to twentieth centuries found that most infanticides were committed by mothers, and that these mothers tended to be young and unmarried. Moreover, he concludes that most were not suffering from mental illness at the time of the infanticides, suggesting that the behavior is not necessarily pathological. Among married women, the most commonly cited motivation for killing newborns was extramarital paternity, whereas the most common motivation for unmarried women was to avoid the negative social consequences of an illegitimate birth. Resnick also notes that killing of infants rather than neonates tended to be done by older mothers whose motivation was to end some real or perceived suffering (e.g., deformed or sickly infants). This bimodal distribution of behaviors suggests that the relationship between infanticide and marital status is contingent not only upon social legitimacy concerns but also broadly upon factors such as maternal age and infant quality.
In her review of infanticide in Western history, Moseley (1985) similarly concludes that infanticide is generally committed by mothers for “social or economic” reasons (although infanticide threat by fathers was reportedly high during Greco-Roman times, as paternal filicide was legally allowed). Daughters were often perceived as an economic liability among poor feudal farmers. In combination with pervasive androcentric ideology, this led to a disproportionately high rate of female infanticide over the course of Western history. Moseley notes that marital status in the Middle Ages modulated acceptability of infanticidal behaviors: unmarried women were harshly punished for committing infanticide, while married women could kill their infants with “relative impunity.” Certain individuals (in this case, married women) were therefore permitted greater control over their reproductive and investment decisions because their offspring were regarded as “legitimate.”
Moseley concludes that the decline of infanticide in Europe was linked to both greater financial stability among the poor and an increased availability of breastfeeding alternatives (e.g., animal milk, artificial formula), which reduced the energetic burden of childrearing. Daly and Wilson (1988) credit the historical fall in English infanticide rates to improvements in social welfare services, access to contraception and legal abortions, and the declining social stigma attached to unmarried mothers.
Contemporary Cross-National Patterns
Drawing statistical inferences from infanticide data is complicated by underreporting, inconsistency in government records (Porter and Gavin 2010), and the relative rarity of the phenomenon. Despite this limitation, records from law enforcement and other government agencies have been used to assess broad patterns of infanticide among industrialized nations during the twentieth and twenty-first centuries. Across nations such as the United States (Overpeck et al. 1998; Oberman 2001), Canada (Daly and Wilson 1988), Italy (Ciani and Fontanesi 2012), Croatia (Marcikić et al. 2006), and Malaysia (Razali et al. 2014), most infanticides are committed by the mother of the infant, many of whom are unmarried or partnerless. In their study of Japanese infanticide, Sakuta and Saito (1981) describe two distinct modes of infanticidal behavior: anomie, in which infants are killed by relatively young, unmarried parents (typically mothers), and mabiki, in which the parents are married and already have children but cannot afford to raise additional offspring. These patterns parallel the difference that Resnick observed between infanticidal behavior by older, married women and younger, unmarried women in historical cases.
Detailed data regarding infanticide in developing nations are scarce. However, the available evidence suggests that general patterns are similar to those seen in developed nations. In South Africa, young mothers are the most common agents of infanticide, but no information is reported regarding marital status (Abrahams et al. 2016). Interviews with couples in Tamil Nadu, India have revealed that most parents considering infanticide are young (between 20 and 30 years of age), are relatively poor, and already have at least one other child (Giriraj 2004, cited in Tandon and Sharma 2006). This cluster of traits suggests that resource stress exerts notable influence upon parental investment. Though more data are needed, resource stress may prove powerful enough to drive investment and termination decisions independent of marital status.
It is also worthy to note that cross-national paternal infanticide data displays somewhat different patterns than maternal infanticide data. Paternal killing of neonates (infants aged less than 28 days) is less frequent. Fathers and stepfathers who kill children instead tend to do so when the children are older (West et al. 2009). The demography of infanticidal fathers may, however, parallel that of infanticidal mothers; for instance, in Canada, infanticidal fathers are generally younger (Daly and Wilson 1988).
Patterns in Small-Scale Societies
Small-scale, nonindustrial societies are often objects of scholarly interest because they tend to be natural fertility populations, as defined by a lack of access to (or use of) commercial contraceptives. The introduction of commercial contraceptives can significantly alter reproductive behavior. Declining fertility in many industrial nations in recent centuries has been attributed in part to the increased availability of commercial contraceptives, safer abortion procedures, family-planning initiatives, and to changing social norms (Sear et al. 2016). Fertility transitions such as these may shift locally optimal life history and parental investment strategies in ways that are drastic and historically anomalous. Moreover, many contemporary industrialized nations have experienced public health breakthroughs, such as sanitary improvements and development of infectious disease prevention, dramatically reducing infant mortality (Stearns 2016). The potential for both greater reproductive agency and lower infant mortality have serious implications in terms of transforming reproductive behavior and parental investment decisions in human populations. Cross-cultural survey of nonindustrial societies has provided a diverse sample that helps to elucidate the relationship between marital status and infanticide in societies that differ in important ways from industrialized nations.
Daly and Wilson (1984) embraced the cross-cultural approach, surveying ethnographic accounts of infanticide in the Probability Sample Files, a stratified sample of nonindustrial cultures selected from 60 world regions. Of these 60 cultural reports, 39 contained information about infanticide (but note that absence of evidence here is not evidence of absence). Daly and Wilson examined the social context in which infanticide occurred. They found that being an “unwed mother” was a recurrent motivation for committing infanticide. A related motivation, “no male support,” was also observed frequently across cultures. In a different cross-cultural study that focused on twin infanticide, mothers were found to be far less likely to kill twins in cultures where they had a high degree of social support (Granzberg 1973).
Culture-specific case studies are also informative. Bugos and McCarthy (1984) describe a similar pattern of infanticide among the Ayoreo of the Gran Chaco region in South America. Some women, due to a lack of guaranteed male support, committed multiple infanticides over the course of their reproductive lives before settling into a stable marriage. Nancy Howell (1979) reported that Dobe !Kung mothers who gave birth before they could safely wean their older children might also opt for infanticide, a possible example of a quantity-quality trade-off. Among the Tarahumara of northwestern Mexico, infanticide may occur when the mother has inadequate male support, when the mother has too many children already, or when the infant is perceived as defective or sickly (Mull and Mull 1987). One of the few detailed, quantitative studies of infanticide in a small-scale society was conducted by Wulf Schiefenhövel among the Eipo, a population of horticulturalists in Highland New Guinea. Schiefenhövel observed an extraordinary rate of infanticide (between 29% and 43%) in a population that he argued was at the limit of its resource base. In interviews with women who committed infanticide, it was determined that extramarital pregnancies, having too many children already, and young maternal age were among the most commonly cited motivations for committing infanticide (Schiefenhövel 1989).
These findings implicate marital status as an important mediator of infanticide, insofar as marital status predicts access to male support, greater material and social resources, and greater social status and acceptance in general. However, there is no single “typical” pattern of infanticide in nonindustrial societies. Investment and termination decisions, as in industrialized nations, are inextricably tied to individualized social and economic concerns and vary based on the support available to mothers.
Patterned relationships between infanticide and marital status can emerge without the need for highly specialized psychological adaptations. A more fruitful approach may be to consider how more generalized parental investment strategies and life history tradeoffs interact with variable socioecological circumstances and individual differences in reproductive and social status.
The specific act of infanticide may or may not benefit the actor’s fitness, whether in an individual case or on average, but the act need not contribute to fitness for a sociobiological analysis to be illuminating. Infanticide can be viewed as one (rare) manifestation of variations in more abstract motivational states such as child-specific parental love and solicitude. Adaptation may then be sought at the level of these more abstract states. (Daly and Wilson 1984)
- Abrahams, N., Mathews, S., Martin, L. J., Lombard, C., Nannan, N., & Jewkes, R. (2016). Gender differences in homicide of neonates, infants, and children under 5 y in South Africa: Results from the cross-sectional 2009 National Child Homicide Study. PLoS Medicine, 13(4), e1002003.CrossRefPubMedPubMedCentralGoogle Scholar
- Bugos, P. E., and McCarthy, L. (1984). Ayoreo infanticide: a case study. In G. Hausfater & S. Hrdy (Eds.), Infanticide: comparative and evolutionary perspectives (pp. 502–520). New York: Aldine.Google Scholar
- Clutton-Brock, T. H. (1991). The evolution of parental care. Princeton: Princeton University Press.Google Scholar
- Daly, M., & Wilson, M. (1984). A sociobiological analysis of human infanticide. Infanticide: Comparative and Evolutionary Perspectives, 487–502.Google Scholar
- Daly, M., & Wilson, M. (1988). Homicide. New Brunswick: Transaction Publishers.Google Scholar
- Giriraj, R. (2004). Changing attitude to female infanticide in Salem. Journal Social Welfare, 50(11), 13–14. 34–35.Google Scholar
- Howell, N. (1979). Demography of the Dobe !Kung (Vol. 35). New York: Academic Press.Google Scholar
- Moseley, K. L. (1985). The history of infanticide in Western society. Issues in Law and Medicine, 1, 345.Google Scholar
- Schiefenhovel, W. (1989). Reproduction and sex-ratio manipulation through preferential female infanticide among the Eipo, in the Highlands of Western New Guinea. In A. E. Rasa, C. Vogel & E. Voland (Eds.), The sociobiology of sexual and reproductive strategies (pp. 170–193). New York: Chapman and Hall.Google Scholar
- Sear, R., Lawson, D. W., Kaplan, H., & Shenk, M. K. (2016). Understanding variation in human fertility: What can we learn from evolutionary demography? Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 371(1692), 20150144.CrossRefPubMedPubMedCentralGoogle Scholar
- Stearns, S. C. (1992). The evolution of life histories (Vol. 249). Oxford: Oxford University Press.Google Scholar
- Stearns, P. N. (2016). Childhood in world history. New York: Routledge.Google Scholar
- Tandon, S. L., & Sharma, R. (2006). Female foeticide and infanticide in India: An analysis of crimes against girl children. International Journal of Criminal Justice Sciences, 1(1), 1–10.Google Scholar
- Trivers, R. L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the descent of man (pp. 136–179). Chicago, IL: Aldine Publishing Company.Google Scholar