Social Selection and the Evolution of Maladaptation

Joel W. McGlothlin* (Corresponding Author), David N. Fisher

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Evolution by natural selection is often viewed as a process that inevitably leads to adaptation or an increase in population fitness over time. However, maladaptation, an evolved decrease in fitness, may also occur in response to natural selection under some conditions. Social selection, which arises from the effects of social partners on fitness, has been identified as a potential cause of maladaptation, but we lack a general rule identifying when social selection should lead to a decrease in population mean fitness. Here we use a quantitative genetic model to develop such a rule. We show that maladaptation is most likely to occur when social selection is strong relative to nonsocial selection and acts in an opposing direction. In this scenario, the evolution of traits that impose fitness costs on others may outweigh evolved gains in fitness for the individual, leading to a net decrease in population mean fitness. Furthermore, we find that maladaptation may also sometimes occur when phenotypes of interacting individuals negatively covary. We outline the biological situations where maladaptation in response to social selection can be expected, provide both quantitative genetic and phenotypic versions of our derived result, and suggest what empirical work would be needed to test it. We also consider the effect of social selection on inclusive fitness and support previous work showing that inclusive fitness cannot suffer an evolutionary decrease. Taken together, our results show that social selection may decrease population mean fitness when it opposes individual-level selection, even as inclusive fitness increases.

Original languageEnglish
Pages (from-to)61-68
Number of pages8
JournalJournal of Heredity
Issue number1
Early online date30 Nov 2021
Publication statusPublished - 1 Jan 2022

Bibliographical note

We thank Kim Hughes and Anjanette Baker for organizing the symposium and editing this theme issue. We thank Andrew Hendry, Andrew McAdam, Josef Uyeda, and two anonymous reviewers for helpful comments on the manuscript.


  • adaptation
  • fundamental theorem of natural selection
  • indirect genetic effects
  • maladaptation
  • social selection


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