Summary
Selection arising from competition for mates or mate choice, creating traits like peacock tails.
In depth
Intrasexual selection means competition within a sex (antlers, fighting) and intersexual selection means mate choice (bright plumage, songs). Traits can reduce survival but increase mating success. The handicap principle suggests costly signals are honest.
It often drives sexual dimorphism.
Darwin proposed it to explain traits that seem harmful, such as the peacock's tail. Explanations include good genes (honest signals of health, as Zahavi's handicap principle suggests), Fisherian runaway (female preferences and male traits co-evolve) and sensory bias. Anisogamy, with small cheap sperm and large costly eggs, predicts competition among males and choosiness in females, with exceptions in species with role reversal such as pipefish and jacanas.
Sperm competition leads to large testes and sperm plugs, and sexual conflict can produce an arms race: in ducks, males evolved long corkscrew penises and females evolved twisting vaginas. Sexual dimorphism is greatest in polygynous species like elephant seals.
Example: studies of peacocks show that females prefer males with more eyespots in the train.
Frequently asked questions
What is Sexual Selection?
Selection arising from competition for mates or mate choice, creating traits like peacock tails.
Which area of biology covers Sexual Selection, and how advanced is it?
Sexual Selection is one of the 53 topics in Evolution. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Evolution of Sex, Reproductive Isolation, Sympatric Speciation.
Can you give an example of Sexual Selection?
Male peacock tail length is correlated with mating success.
What should I learn before Sexual Selection?
Work through the Beginner topics in Evolution first, such as Evolution, Natural Selection, Charles Darwin, then return to Sexual Selection. Intermediate topics assume the Beginner vocabulary.
What topics are related to Sexual Selection?
The closest topics to Sexual Selection are Evolution of Sex, Reproductive Isolation, Sympatric Speciation, Evolutionary Trade-offs. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Sexual Selection?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Sexual Selection. To practise the whole of Evolution, use the Evolution quiz.
How is Sexual Selection different from Evolution of Sex?
Sexual Selection: Selection arising from competition for mates or mate choice, creating traits like peacock tails. Evolution of Sex: Hypotheses explain why sexual reproduction persists despite its costs, including the Red Queen and mutation clearance. Read both side by side and note what each one explains.
How should I study Sexual Selection step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Evolution of Sex and explain the difference aloud. Finally, take the Evolution quiz and come back to this page for any question you miss.