What is the negative impact of beauty contests on society?
While preferences for certain physical features do have a basis in evolution and reproduction, most ideals or standards of beauty are culturally dependent and heavily shaped by notions of class, purity, race and ethnicity, gender norms, and abelist body norms.
From an evolutionary standpoint, certain physical features or phenotypes (how the genes manifest themselves) are indicative of reproductive fitness. Features such as facial symmetry, having all of one's teeth, and even certain bodily proportions can indicate to others that someone is genetically fit. In non-cultural animals, this may manifest as the largest males of a species having better access to females because he can fight off other potential mates. Traits like being able to camouflage or having large teeth or horns can also be advantageous in the long-game of reproduction.
Only so much of human beauty ideals are determined by evolutionary advantage, though. In a way, the human preference for certain types of beauty is a very drawn out and complex means of determining reproductive fitness. Because this fitness is culturally determined and dependent upon beliefs about gender, race, class, and so on, there is no real guarantee of this perceived fitness. Such characteristics are much more indicative of social success than reproductive. It is because certain characteristics are held as beautiful that they contribute to social success, but not necessarily reproductive.
For example, many cultures favor women with light skin as beautiful. Historically, having lighter skin has been indicative of class, as people who worked in the fields were darker from sun exposure. Even today, light skin in women is favored as a sign of a leisurely lifestyle, one that is lower in physical stress compared to that of someone who labors outdoors. A woman with light skin may be considered more beautiful and thus have an easier time navigating certain social spheres, but it is no real indicator of her levels of physical stress and reproductive capability.
Some other things to consider are face shape, eye and hair color, height, and body shape. Much of the modern, Western beauty ideal has its origins in the colonial period, where the ruling class was primarily composed of fair-skinned, light-haired people from Europe. Part of this Eurocentric beauty ideal is influenced by the fact that it contrasted with the populations of dark-haired, dark-skinned, colonized people. Western culture also holds physically fit, able bodies with "appropriate" amounts of fat as the ideal of beauty. This is influenced by beliefs of excess and morality- oftentimes excess body fat is equated with glutton and sin. Able-bodiedness has a long history of being a beauty ideal, as up until the past few centuries, people who were impaired in some way did not typically survive. Even if they did live to adulthood, they rarely had children. Life was too demanding and stressful for someone with an impairment to keep up. Unfortunately, even though much of the world can accommodate people with physical limitations, beauty ideals still often exclude people who have these impairments.
Beauty contests are controversial because they reward people for fitting into an essentially random set of determinants for beauty. Genetics functions through the processes of randomization and mutation to come up with the most adaptations as possible, in the hopes that one phenotype might offer better fitness. Even though there are definite patterns of hereditary traits (for example, I inherited brown hair from my father), those which are deemed to be "most beautiful" is highly variable from one culture to another. Beauty contests serve to reinforce arbitrarily determined standards of beauty, and equate this beauty with success.
From a feminist point of view, beauty contests motivate and reward women for fitting into these beauty categories which may be unattainable for a significant portion of the population. It equates women's success with beauty and detracts from achievement in other areas of life. Placing such an importance on beauty and a beauty contest mindset contributes to the attitude that even if a woman is successful in her career, she will not be respected unless she is beautiful. Beauty contests reinforce the belief that a woman's value is dependent upon her ability to fit into very restrictive and oppressive beauty ideals.