Final answer:
Antagonistic sexual selection is the evolutionary process where adaptations beneficial to one sex may harm the other, leading to an evolutionary 'arms race' and significant sexual dimorphism. Traits may evolve that enhance reproductive success at survival costs, exemplified by the peacock's large tail.
Step-by-step explanation:
When reproductive interests between males and females of the same species differ, such as in fruit flies, leading to adaptations that benefit one sex but are detrimental to the other, a type of sexual selection known as antagonistic sexual selection occurs. This form of selection drives the evolution of features that may provide a reproductive advantage to one sex but can cause disadvantages to the other, initiating an evolutionary arms race of sorts where one sex evolves counter-adaptations to negate the effects of the other's adaptations.
Sexual dimorphism often results from such antagonistic sexual selection, with the most evident examples observed in animal populations, where there may be significant differences in male and female reproductive success. Males might become larger, more aggressive, or develop showy ornaments to attract females or ward off rival males. Conversely, females will often evolve preferences or reproductive strategies that allow them to select for the most beneficial traits in potential mates. These adaptations can sometimes be so exaggerated that they end up being detrimental in other aspects of the individual's survival, such as the peacock's large tail which, while attractive, also increases predation risk.