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Twinning in Norway Following the Oslo Massacre: Evidence of a "Bruce Effect' in Humans
Univ Calif Berkeley, Sch Publ Hlth, 50 Univ Hall, Berkeley, CA 94720 USA..
Santa Clara Univ, Dept Biol, Santa Clara, CA USA..
Univ Calif Berkeley, Dept Demog, Berkeley, CA 94720 USA..
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Institute for Housing and Urban Research.
2016 (English)In: Twin Research and Human Genetics, ISSN 1832-4274, E-ISSN 1839-2628, Vol. 19, no 5, 485-491 p.Article in journal (Refereed) Published
Abstract [en]

Emerging theory and empirical work suggest that the Bruce Effect', or the increase in spontaneous abortion observed in non-human species when environments become threatening to offspring survival, may also appear in humans. We argue that, if it does, the effect would appear in the odds of twins among male and female live births. We test the hypothesis, implied by our argument, that the odds of a twin among male infants in Norway fell below, while those among females rose above, expected levels among birth cohorts in gestation in July 2011 when a deranged man murdered 77 Norwegians, including many youths. Results support the hypothesis and imply that the Bruce Effect operates in women to autonomically raise the standard of fetal fitness necessary to extend the gestation of twins. This circumstance has implications for using twins to estimate the relative contributions of genes and environment to human responses to exogenous stimuli.

Place, publisher, year, edition, pages
2016. Vol. 19, no 5, 485-491 p.
Keyword [en]
selection in utero, twins, evolution, Bruce Effect
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-306751DOI: 10.1017/thg.2016.58ISI: 000384428600010PubMedID: 27453297OAI: oai:DiVA.org:uu-306751DiVA: diva2:1045570
Available from: 2016-11-10 Created: 2016-11-03 Last updated: 2016-11-10Bibliographically approved

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Hartig, Terry
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