Handicap Principle
links: Darwinian Evolutionary Theory
Based on sexual selection theory
Big tails, large antlers, bright colors, and the like tend to handicap males who have these ornate features.
Males who can afford to maintain these exaggerated, costly impediments honestly signal to females that they are healthy specimens from good genetic stock.
For example, male peacocks that have more elaborate tails produce both more offspring and healthier offspring than do their tail-challenged male competitors (Petrie, 1994; Petrie and Halliday, 1994).