In Darwinian theory of evolution sexual selction refers to the way that preferences of mating partners drives evolutionary changes, as individuals that are more attractive to potential partners are more likely to breed. This can lead to runaway effects, where a trait that is originally a signal for a good survival characteristics (e.g. feathers looking healthy and in good condition) can give rise to an arms race whereby it becomes an end in itself to the point that it can be damaging to the individual and species. The most well known example of this are peacock tail feathers.
Used on Chap. 23: page 572
Jatin Sindhu, CC BY-SA 4.0, via Wikimedia Commons
