Sexual Dimorphism

David Punzalan and David Hosken, researchers at the Center for Ecology and Conservation at the University of Exeter in the UK, have defined sexual dimorphism as the obvious differences in male and female physiology, behavior, and morphology. The study further explains that the differences in appearance between males and females of the same species, which is called sexual dimorphism, can actually make an animal go extinct, instead of ensuring survival by making them more attractive mates. Risk Of Extinction

As a result, species with greater sexual or physical differences went extinct for up to 10 times compared to species with typical appearances. In Darwin's theory of survival of the fittest, sexual dimorphism has become closely related to sexual selection, a phenomenon in which animals choose their partners based on its sex-specific viability. The best example of sexual dimorphism can be seen in peacocks. The bigger the tail of the male peacock, the more attractive it becomes to the peahen. Other research has found that huge horns and bone frills in some dinosaurs were meant to make them more attractive to their mates, rather than being used in fights with other males. "The evolutionary costs of such traits help to enforce the honesty of the associated displays, but can also reduce the fitness of populations in general and thereby increase the risk of [the]population," the researchers of University wrote, according to Tech Times. A research published this week in the journal Nature reported that sexual selection in ancient animals determined which species will survive or go extinct. Fossils of 93 species of ostracods that existed some 84 million years ago during the Late Cretaceous period were analyzed based on their physical traits and the approximate time of extinction. They concluded that male ostracods, also known as seed shrimp, evolved heavily in terms of their appearance to the point that they missed out on other survival factors. The research "provides a strong indication, and the first good documentation from the fossil record, that sexual dimorphism tends to increase extinction risk," said Jonathan Payne, a geological sciences professor at Stanford University. Also, the researchers said that the ostracods' size and their ability to regulate body temperature were major hurdles for the study.
A study in Nature shows species which are visually unusual or attractive go extinct at higher rates.