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Homology, Genes, and Evolutionary Innovation$
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Günter P. Wagner

Print publication date: 2014

Print ISBN-13: 9780691156460

Published to Princeton Scholarship Online: October 2017

DOI: 10.23943/princeton/9780691156460.001.0001

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Digits and Digit Identity

Digits and Digit Identity

(p.356) 11 Digits and Digit Identity
Homology, Genes, and Evolutionary Innovation

Günter P. Wagner

Princeton University Press

This chapter investigates the evolutionary and developmental biology of digits, focusing on what these appendages can teach us about character identity and character origination. The idea that digits have individuality and that it is meaningful to distinguish between the thumb, the index finger, and all the other digits is both intuitive and controversial. With it arise questions regarding how digits evolved, how they were gained, lost, and then possibly regained, and whether or not they had changed place in the limb. The chapter first considers the origin of digits, with emphasis on the issue of the nature of the pentadactyl limb, before discussing the developmental and morphological heterogeneity of the tetrapod hand. It also examines digit loss and re-evolution in amniotes, the pentadactyl autopodium type, and developmental developmental genetics of digit identity. It suggests that the “tetrapod limb” is likely the result of a dynamic evolution of character identities.

Keywords:   evolution, developmental biology, digits, character identity, character origination, pentadactyl limb, tetrapod hand, digit loss, autopodium, digit identity

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