Standard Article

Natural Selection: Sex Ratio

  1. Jon Seger

Published Online: 19 APR 2001

DOI: 10.1038/npg.els.0001719



How to Cite

Seger, J. 2001. Natural Selection: Sex Ratio. eLS. .

Author Information

  1. University of Utah, Salt Lake City, Utah, USA

Publication History

  1. Published Online: 19 APR 2001


Natural selection acts strongly on the proportional numbers of male and female offspring among the progeny of adults. The equilibrium is often one at which males and females are produced in roughly equal numbers, but under certain ecological and genetic circumstances there may be dramatic population-wide biases, and even in populations with balanced sex ratios, parents are often selected to produce strongly male- or female-biased progenies in response to variations in their individual condition.


  • evolutionarily stable strategy;
  • ESS;
  • frequency-dependent selection;
  • local mate competition;
  • reproductive conflicts;
  • resource allocation;
  • social insects