Why children from the same family are so different from one another

Author(s): Quinsey, V. L., Craig, W. M.

Journal/Book: Hum Nature-Int Biosoc Perspec. 1996; 7: 200 Saw Mill River, Hawthorne, NY 10532. Aldine de Gruyter Division Walter de Gruyter Inc. 281-290.

Abstract: The well-established finding that siblings growing up in the same family turn out to be very different from one another has puzzled psychologists and behavior geneticists alike. In this theoretical note we describe the possible ontogeny and phylogeny of a sibling differentiation mechanism. We suggest that sibling competition for parental investment results in sibling differentiation on a number of characteristics, producing different developmental trajectories within families. Variations in developmental trajectories within families may have had fitness advantages in ancestral environments because (a) sibling competition for extrafamilial resources would be reduced and (b) these variations would be suited to environments containing a variety of niches or to changing environments. Predictions derived from this model and an example of an application to attachment theory are presented.

Note: Article ML Lalumiere, Penetanguishene Mental Hlth Ctr, Res Dept, 500 Church St, Penetanguishene, on L9M 1G3, Canada

Keyword(s): behavior genetics; development; evolution; family; individual differences; nonshared environment; parental investment; siblings; LAST HALF; LIFE-SPAN; ENVIRONMENT; SIBLINGS; TWINS; SOCIALIZATION; INTELLIGENCE; EXPERIENCE; SIMILARITY; ATTACHMENT

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Why children from the same family are so different from one another - A Darwinian note