Chapter

Why Siblings Are Like Darwin’s Finches: Birth Order, Sibling Competition, and Adaptive Divergence within the Family

Frank J. Sulloway

in The Evolution of Personality and Individual Differences

Published in print November 2010 | ISBN: 9780195372090
Published online May 2011 | e-ISBN: 9780199893485 | DOI: https://dx.doi.org/10.1093/acprof:oso/9780195372090.003.0004
Why Siblings Are Like Darwin’s Finches: Birth Order, Sibling Competition, and Adaptive Divergence within the Family

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This chapter explores the developmental process of strategic niche specialization further, within the context of family dynamics, specifically inter-sibling competition. In a Darwinian world, sibling competition over parental investment represents a powerful engine of phenotypic novelty, causing siblings to behave differently from one another in their efforts to garner the resources needed for survival and reproductive success. Such differences in personality are analogues of the disparities in morphological traits, such as bill size and shape among birds, that relentlessly drive the evolution of species in nature. Although they are typically modest, the magnitude of the various individual personality differences that are associated with disparities in parental investment, as well as with differences in such factors such as birth order and gender, is about the same size as morphological selection differentials found in the rest of nature. Such individual personality differences provide a more-than-sufficient basis for natural selection to operate on sibling behavior and strategies within the family.

Keywords: sibling competition; family dynamics; niche specialization; natural selection; sibling behavior

Chapter.  12603 words.  Illustrated.

Subjects: Psychology

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