Natural Selection Vs Sexual Selection

Charles Darwin’s most famous evolutionary findings and theories were published in two books: On the Origin of Species and The Descent of Man and Selection in Relation to Sex. In the former, he presents his theory of natural selection that results from the struggle to survive (On the Origin of Species, 175). In the latter, he explains sexual selection that results from the struggle to reproduce. According to Darwin, natural selection is one the basic agents of evolutionary change. At the same time, sexual selection is divided into the two aspects of intrasexual and intersexual selection. In essence, natural selection involves the success of both sexes with respect to their environment while sexual selection involves the choice of the female
He first observed that all organisms on the planet produce more offspring that would be needed to replace them such that it would lead to overpopulation, however, their numbers are kept in check. Each emerging population will compete for scarce resources and that many of the offspring die to allow the eventual adult population to roughly stay the same. This is due to the limitation of resources such as food, shelter, air, light, water, and mating areas. It was Thomas Malthus’s publication of Essay on the Principle of Population (6th edition, 1828) that led Darwin to this deduction: human populations are increasing at a rate that resources eventually could not sustain. This led Darwin to infer that individuals compete for resources in order to survive. He then, through his observations on barnacles and even people, concluded that individuals vary and are each unique (On the Origin of Species, 201). He noticed that offspring, over each generation, naturally show small variations or differences in comparison to their parents and coined the term gradualism (On the Origin of Species, 388). In addition, he crossed various breeds of pigeons and also gathered data from other breeders to deduce that these individual variations are heritable such that they are passed from one
In other words, attractive female physical features including artificial ones such as make-up and jewellery have higher chances of mating success with differences and preferences due to various cultures around the world. In addition, he stated that since humans have more developed brains, their free choice allows them to pick superficial traits that may not necessarily be natural or physical, “…he is impelled by nearly the same motives as the lower animals when left to their own free choice, though he is in so far superior to them that he highly values mental charms…” (The Descent of Man, 559). And for Darwin, men are more intelligent, faster, and stronger than women. However, female choice is still important as he infers that slavery of women interferes with sexual selection. In this way, he described the differences between various races of humans to be the result of sexual selection. Furthermore, people have different standards of beauty depending on their cultures and countries, all with the sole aim of attracting members of the opposite sex (The Descent of Man, 542). This is in fact logically inconsistent with his theory about nature whereas he defines sexual and natural selection as not being due to an intelligent force, he defines humans, both men and women, as having free will and being able to pick traits they so desire as