Sexual selection is a concept which was coined by Charles Darwin and deals with the differential mating success between individuals based on their abilities to find and secure mates. Sexual selection is similar to natural selection, but differs because it is based on the struggle for reproduction rather than the struggle for survival.
It is common for the males of different species to develop fitness signals which do not assist them in survival, but help them reproduce. These traits serve to either attract mates (intersexual selection) or to intimitate rivals (intrasexual selection). Essentially, intersexual selection is based on males developing traits which females find attractive since “sexier” males will be preferred by females. Conversely, intrasexual selection allows males to display their aggressiveness to females by fighting with potential suitors.
When considering sexual selection, females are viewed as a limited resource. Females are the limiting resource because they invest the most in producing offspring. For males, passing on their genes is critical to increasing their fitness and leaving a legacy. Thus, it is critical for males to compete for this limited resource. Females do not invest energetically in this type of sexual selection because they have to invest heavily in producing high quality eggs.
The male peacock’s elaborate tail is a classic example of sexual selection. The tail serves as an energetically costly courtship tool to attract females and has no survival advantage. Rather, a peacock's tail limits survival abilities. The tail serves as an honest fitness signal indicating to females that a male peacock is of high quality if they are able to produce an embellished tail and still survive. However, less fit peacocks cannot produce tails as large because it is too much of a fitness barrier and poses difficulties in garnering resources.
Furthermore, humans use fitness signals as mating tactics as well. For example, humans display the creativity of their minds through art and music, or their strength through sports, to prove that they are worthy mates. It is costly for a female to not only invest in an egg, but to give birth and care for a child. Thus, it is an expensive mistake for females to mate with an uncommitted and low-quality male.
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