The theory of sexual selection has been in development for over 150 years to explain the world around us readily. To gain macroscopic understanding, one must understand sexual selection at the microscopic level. Research on sexual selection should therefore start with anisogamous gametes. The evolution of anisogamy gave rise to not only morphologically diverse gametes. With anisogamy, the concept of sex and inherent differences between the sexes came to life too. Inherent differences between the sexes are the reason for sexual conflict, and sexual conflict, together with sexual selection, generates various traits. As time goes by, traits such as vibrant colors, pleomorphic phenotypes, and courtship change. Moreover, access to sexual partners, just like to any other environmental resource, isn’t constant. Fluctuations in interactions between sexes hence result in coevolution between sexes. Coevolving traits aim to increase reproductive success. Oftentimes, neither sex wins the evolutionary arms race by having a colossal number of offspring. However, consequences of the evolutionary arms race, such as speciation and possibly bird flight, can be of significant proportions