Strong mothers bear more sons in rural Ethiopia

Gibson, Mhairi A.; Mace, Ruth

doi:10.1098/rsbl.2003.0031

Cited by 97 publications

(73 citation statements)

References 18 publications

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“…Such demand may be imposed either directly, through behaviors that solicit forms of investment as in Angelman syndrome, or indirectly, through selforiented, non-social behavior that precludes or delays physical independence, requiring mothers or others to provide longer-term, more highly-intensive care. This 18 hypothesis is concordant with several lines of evidence, including: (1) accelerated brain and body growth in young children with autism and increased relative effects from paternally-expressed imprinted genes (Crespi and Badcock 2008), (2) imprinted gene effects on reaction to novelty, and dispersal, in mice (Isles et al 2002;Plagge et al 2005), (3) a higher incidence of autism in males, who are more costly than females to rear (Gibson and Mace 2003;Rickard et al 2007;Tamimi et al 2003), (4) myriad reports of close and sustained, if atypical, relationships between mothers and their autistic children (e. g., Hoffman et al 2009), and (5) temperaments of autistic children that involve higher rates of activity, impulsivity, and non-compliance (e. g., Garon et al 2009).…”

Section: Autism and Attachmentsupporting

confidence: 66%

The Strategies of the Genes: Genomic Conflicts, Attachment Theory, and Development of the Social Brain

Crespi

2011

Brain, Behavior and Epigenetics

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I describe and evaluate the hypothesis that effects from parent-offspring conflict and genomic imprinting on human neurodevelopment and behavior are central to evolved systems of mother-child attachment. The psychological constructs of Bowlby's attachment theory provide phenomenological descriptions of how attachment orchestrates affective-cognitive development, and patterns of imprinted gene expression and co-expression provide evidence of epigenetic and evolutionary underpinnings to human growth and neurodevelopment. Social-environmental perturbations to the development of normally-secure attachment, and alterations to evolved systems of parent-offspring conflict and imprinted-gene effects, are expected to lead to specific forms of maladaptation, manifest in psychiatric conditions affecting social-brain development. In particular, under-development of the social brain in autism may be mediated in part by mechanisms that lead to physically enhanced yet psychologically under-developed attachment to the mother, and affective-psychotic conditions, such as schizophrenia and depression, may be mediated in part by forms of insecure attachment and by increased relative effects of the maternal brain, both directly from mothers and via imprinted-gene effects in offspring. These hypotheses are concordant with findings from epidemiology, attachment theory, psychiatry, and genetic and epigenetic analyses of risk factors for autism and affective-psychotic conditions, they make novel predictions for explaining the causes of psychosis in Prader-Willi syndrome and idiopathic schizophrenia, and they suggest avenues for therapeutic interventions based on normalizing alterations to epigenetic networks and targeting public-health interventions towards reduction of perturbations to the development of secure attachment in early childhood and individuation during adolescence.

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Section: Autism and Attachmentsupporting

confidence: 66%

The Strategies of the Genes: Genomic Conflicts, Attachment Theory, and Development of the Social Brain

Crespi

2011

Brain, Behavior and Epigenetics

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“…Three independent measures of household wealth and status were included: land holding size, total number of fathers' marriages, and sibling sex ratio at birth (including dead siblings). The latter was included as a previous study had indicated that a secondary sex ratio biased toward males was a measure of well-being in this population (46).…”

Section: Methodsmentioning

confidence: 99%

Land inheritance establishes sibling competition for marriage and reproduction in rural Ethiopia

Gibson

Gurmu

2011

Proc. Natl. Acad. Sci. U.S.A.

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Intergenerational transfer of wealth has been proposed as playing a pivotal role in the evolution of human sibling relationships. Sibling rivalry is assumed to be more marked when offspring compete for limited heritable resources, which are crucial for reproductive success (e.g., land and livestock); whereas in the absence of heritable wealth, related siblings may cooperate. To date, comparative studies undertaken to support this evolutionary assumption have been confounded by other socioecological factors, which vary across populations, e.g., food sharing and intergroup conflict. In this article we explore effects of sibling competition and cooperation for agricultural resources, marriage, and reproduction in one contemporary Ethiopian agropastoralist society. Here recent changes in land tenure policy, altering transfers of land from parents to offspring, present a unique framework to test the importance of intergenerational transfers of wealth in driving sibling competition, while controlling for socioeconomic biases. In households where land is inherited, the number of elder brothers reduces a man's agricultural productivity, marriage, and reproductive success, as resources diminish and competition increases with each additional sibling. Where land is not inherited (for males receiving land directly from the government and all females) older siblings do not have a competitive effect and in some instances may be beneficial. This study has wider implications for the evolution of human family sizes. Recent changes in wealth transfers, which have driven sibling competition, may be contributing to an increased desire for smaller family sizes.

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“…Weak relationships between sex ratios and the nutritional resources of mothers in late pregnancy and postnatally have been reported (Gibson & Mace 2003;Tamimi et al 2003) but are controversial (Stein et al 2003). Even if real, they do not imply any maternal command over foetal sex.…”

Section: Introductionmentioning

confidence: 99%

You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans

2008

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Facultative adjustment of sex ratios by mothers occurs in some animals, and has been linked to resource availability. In mammals, the search for consistent patterns is complicated by variations in mating systems, social hierarchies and litter sizes. Humans have low fecundity, high maternal investment and a potentially high differential between the numbers of offspring produced by sons and daughters: these conditions should favour the evolution of facultative sex ratio variation. Yet little is known of natural mechanisms of sex allocation in humans. Here, using data from 740 British women who were unaware of their foetus's gender, we show that foetal sex is associated with maternal diet at conception. Fifty six per cent of women in the highest third of preconceptional energy intake bore boys, compared with 45% in the lowest third. Intakes during pregnancy were not associated with sex, suggesting that the foetus does not manipulate maternal diet. Our results support hypotheses predicting investment in costly male offspring when resources are plentiful. Dietary changes may therefore explain the falling proportion of male births in industrialized countries. The results are relevant to the current debate about the artificial selection of offspring sex in fertility treatment and commercial 'gender clinics'.

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Strong mothers bear more sons in rural Ethiopia

Cited by 97 publications

References 18 publications

The Strategies of the Genes: Genomic Conflicts, Attachment Theory, and Development of the Social Brain

The Strategies of the Genes: Genomic Conflicts, Attachment Theory, and Development of the Social Brain

Land inheritance establishes sibling competition for marriage and reproduction in rural Ethiopia

You are what your mother eats: evidence for maternal preconception diet influencing foetal sex in humans

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