Yes, there are instances where both males and females exhibit traits influenced by sexual selection. While it's common for one gender (usually males) to have more pronounced traits, both genders can develop them in species where both compete for mates or where mutual selection occurs. For instance, in some bird species, both males and females have bright plumages and engage in complex mating dances. This bi-directional selection ensures that both sexes invest in traits that enhance their mating success, leading to mutual evolution of pronounced traits.

Females play a crucial role as selective agents in sexual selection, especially in species where males are the ones displaying extravagant traits. In many cases, females exercise choice in their mates, selecting those with the most appealing or pronounced features. This choice can be based on various criteria: strength, health, ability to provide, or purely aesthetic appeal. As females consistently choose males with specific characteristics, those traits become more prevalent in the population. Therefore, even though females might not display these traits themselves, their preferences drive the evolutionary trajectory of those traits in males.

Sexual dimorphism, where two sexes of the same species exhibit different physical or behavioural characteristics, is often a direct result of sexual selection. For example, male lions have manes, while females do not; male peacocks have elaborate tail feathers, while females have subdued colours. This dimorphism arises because of differing selective pressures on the two sexes, typically revolving around competition for mates in males and choice in females. The traits that get exaggerated in one sex are often those that are advantageous in the mating game, be it for fighting rivals or attracting a partner.

Absolutely. Humans, like all species, are subject to the forces of evolution, including sexual selection. Physical attributes such as facial symmetry, body proportions, and even certain behavioural traits can be influenced by sexual selection. Historically, traits that indicated health, fertility, or good genes might have been preferred in mates, leading to the propagation of those traits in the population. While modern society has added layers of complexity with cultural and social norms, the fundamental evolutionary mechanisms, including sexual selection, still play a role in shaping human preferences and attributes.

Sexual selection can lead to the evolution of traits that might seem disadvantageous from a pure survival standpoint. This happens because these traits provide a reproductive advantage, ensuring that genes are passed on to the next generation. For example, a long and bright tail feather in a bird might make it more visible to predators, but if it helps attract more mates, the reproductive benefit can outweigh the survival cost. Over time, as these traits get passed down through generations due to higher mating successes, they become prominent in the population, even if they come with certain risks.