Species that are highly attractive or different have higher risks of extinction compared to those that blend similarly with the rest, a new study finds.
A research published this week in the journal Nature reported that sexual selection in ancient animals determined which species will survive or go extinct.
Peacocks, for example, have evolved with big colorful tails. The bigger their tails, the more attractive they become to the opposite sex.
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.
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.
There are two contrasting evolution models related to sexual selection. One suggests that dimorphism actually helps species adapt to their environment; thus, making them less likely to become extinct. The other states that exaggerated physical traits make them a target for predators.
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.
"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 wrote.
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.
Researchers found that male ostracods, also known as seed shrimp, evolved heavily in terms of their appearance to the point that they missed 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.
However, Payne further said that information from the fossilized ostracods may not necessarily apply to human beings and other animals. Researchers cited the ostracods' size and their ability to regulate body temperature in water as major limitations of the study.