Sexual Selection

Define sexual selection

the struggle for mates -- certain traits have evolved in response to selection on mating success.

Text, video, lecture

Describe the conditions that led to sexual selection

Fundamental difference between sexes in the relative investment in individual offspring. Typically: Females gain little from multiple matings.

But: males stand to gain a great deal from multiple matings.

Describe the consequences of sexual selection

Competition among the same sex for access to mates via combat (leading to size dimorphism), sperm competition, and/or infanticide

Competition to attract mates. There is choice by one sex among mates of the other sex. Females (or more limited sex) do actively choose mates.

Good genes hypothesis

Gray tree frog

Sensory bias

Water mites

Know that the female is not always the limiting sex

Sex role reversal in jacanas

Humans?

Describe the runaway selection hypothesis

Malaysian stalk-eyed flies

Human brains

Be able to describe why hypotheses about human behavior invoking sexual selection require extra care in testing

It is easy to accept a hypothesis as “true” when in conforms to your preconceived ideas. When genders are unequal in power in society, it is important to be careful in assessing data and conclusions.