A new theory of sexual investment

  • Smith J
  • 86


    Mendeley users who have this article in their library.
  • 200


    Citations of this article.


It is argued that an appropriate model for the evolution of sexual investment, at least in higher vertebrates, may be as follows. The primary sex ratio is fixed at unity, parents can recognise the sex of individual offspring, and the returns (in offspring fitness) are different for the two sexes. For this model, it is shown that it is evolutionarily stable to invest differently in sons and daughters. In particular: If for a given investment the probability of survival is lower for one sex, selection favours greater investment in that sex. If one sex has a frequency-dependent component of fitness, such that individuals receiving a greater-than-average investment are fitter, selection favours greater investment in that sex. If the sex of an offspring can be recognised after an investment d, it may be evolutionarily stable to invest only in some fraction r of the more expensive sex, and to abandon a fraction (1-r). However, such behaviour can evolve only if d is a small fraction of the total investment required per offspring.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document


  • J. Maynard Smith

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free