Sexual dimorphism is a form of sex difference between males and females. It is found in most animals and some plants. Males and females have distinctly different body sizes and brains.
Sexual dimorphism is caused by evolution. In addition to its physical effects, sexual dimorphism also affects many aspects of a person’s personality.
Body size differences between males and females
Body size differences between males and females are common across animal phyla, and they have been a topic of considerable interest among evolutionary biologists. In many animal species, body size is a function of habitat and trophic structure, and it usually results from competition and female selection.
However, the reasons behind the differences are not clear. The differences may be due to a difference in diet, or to sexual selection. In some animals, the differences are caused by diet specialization or by the male’s behavior. In other species, sexual selection may be responsible for the difference in size.
In many animals, body size differences between males and females correlate with their mean body size. This trend was first described by Rensch (1959). The more male-dominated a clade is, the greater the body size differences between males and females. Similarly, size dimorphism decreases with increasing female size.
Genetic and environmental factors can also contribute to size differences. Diet may reduce the size difference between males and females under nutritional stress. In contrast, a healthier diet can increase the M/F ratio. These are important factors that affect the development of sexual dimorphism in humans.
The most extreme example of sexual dimorphism is found in peafowl. The male peacocks have flamboyant tail feathers, while their female counterparts are mostly brown, gray, or cream in color. The peacock males fan out these tail feathers before mating, but the females are more able to blend in and hide from predators.
Differences in brain size between males and females
While the differences between male and female brains are not as drastic as people may think, some differences do exist. For instance, men have a slightly larger brain than women. But the difference does not have any effect on their intelligence. Men tend to have a larger inferior-parietal lobule, which is associated with solving mathematical problems and judging speed. Women have smaller brains, which is important because it allows them to have a higher gray matter to white matter ratio. In addition, their smaller brains also allow them to have a higher ratio of connections between cerebral hemispheres.
Researchers conducted an extensive analysis of MRI data sets from three to 27 years to investigate the sex differences. The team looked at 13 different measurements of brain volume and thickness in both sexes. They found that these differences were not consistent across studies. Moreover, the researchers found that male and female brains had a similar total brain volume.
MRI studies have revealed that male brains are slightly bigger than females. However, this difference does not last throughout the adulthood. Male brains are 10% larger than female brains. This difference may have more to do with the gender of the brain.
Evolutionary processes that produce sexual dimorphism
Sexual dimorphism is a systematic difference in form between male and female organisms of the same species. It can be a matter of colour, structure, size, or even behavior. It is caused by the inheritance of sexual traits in the genetic material. It can be advantageous for some animals while being harmful for others.
Some species exhibit sexual dimorphism in order to improve reproductive success, such as female insects, which are usually larger than males. Similarly, female woodpeckers have different-sized and shaped beaks, which help them find insects in different layers of bark.
Evolutionary processes that produce sexual dimorphismm can be categorized into two main types: intrasexual and intersexual selection. Intrasexual selection occurs during direct encounters between two or more individuals. This type of selection has been shown to produce sexual dimorphism in secondary sexual characteristics. Males, for example, compete with each other to attract a female.
Sexual selection also affects the ability of individuals to provide parental care. Some species exhibit greater parental care than others. This has implications for reproductive success, fertilization success, and the care of offspring. Changing the parental care of a sex can lead to a large variation in the reproductive success of a species.
Sexual dimorphism is a complex process involving differences in body size, color, and parasitic load. It is an incredibly striking source of variation.
