Runaway selection is a concept in evolutionary biology where certain traits become exaggerated over generations due to sexual selection. This occurs when one sex, typically females, prefers specific traits in the other sex, such as bright colors or elaborate displays. As a result, individuals with these preferred traits are more likely to reproduce, leading to an increase in those traits in the population. Over time, this preference can lead to extreme characteristics that may not necessarily provide survival advantages. For example, the long tail of a peacock may attract mates but can also make it more vulnerable to predators. Thus, runaway selection illustrates how sexual preferences can drive the evolution of certain traits beyond their practical utility.