There is no fitness but fitness, and the lineage is its bearer

Erol Akçay, Jeremy Van Cleve

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Inclusive fitness has been the cornerstone of social evolution theory for more than a half-century and has matured as a mathematical theory in the past 20 years. Yet surprisingly for a theory so central to an entire field, some of its connections to evolutionary theory more broadly remain contentious or underappreciated. In this paper, we aim to emphasize the connection between inclusive fitness and modern evolutionary theory through the following fact: inclusive fitness is simply classical Darwinian fitness, aver aged over social, environmental and demographic states that members of a gene lineage experience. Therefore, inclusive fitness is neither a generaliz ation of classical fitness, nor does it belong exclusively to the individual. Rather, the lineage perspective emphasizes that evolutionary success is determined by the effect of selection on all biological and environmental contexts that a lineage may experience. We argue that this understanding of inclusive fitness based on gene lineages provides the most illuminating and accurate picture and avoids pitfalls in interpretation and empirical applications of inclusive fitness theory.

Original languageEnglish
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1687
StatePublished - Feb 5 2016

Bibliographical note

Publisher Copyright:
© 2016 The Author(s) Published by the Royal Society. All rights reserved.


  • Class structure
  • Hamilton’s rule
  • Inclusive fitness
  • Invasion fitness
  • Lineage
  • Non-additive interactions

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences


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