Sex Protects Against Parasites


Sexual reproduction allows the organism to create new combinations of genes to stay one step ahead parasites. Studying sexual habits of worms, scientists found that species with asexual reproduction were exposed to bacterial infections that destroyed them. US researchers who studied the sex lives of worms, found that sexual reproduction makes organisms more resistant to parasites.


The idea that sexual reproduction might provide protection from pathogens is not a new one. This theory has its roots in a set of ideas known as the Red Queen Hypothesis.

Scientists believe they have discovered the most convincing evidence to date of a key theory in evolutionary biology that sex evolved, because it allows the body to create new combinations of genes to stay one step ahead of the parasites. Asexual reproduction, biological process by which an organism creates a genetically identical copy of itself without combining genetic material with another individual has far greater meaning.

It is much simpler, because there is no need of finding and seducing a partner, fight with rivals and there are no hazards from getting sexually transmitted diseases. The fact that some organisms live long enough to be able to reproduce is because they have first-class genes.

Why then would have risked to “dilute” these good genes with potentially weaker genetic material?

Multicellular organisms cannot mutate themselves on a per infection basis, so we depend on other mechanisms of battling quickly mutating bugs. The genetic variation that we, as a species, get from sexual reproduction is particularly important for the ability of our immune system to fight pathogens. In fact, the most variable set of genes in the human genome encode proteins that determine what kinds of pathogens an individual is best at fighting.

This variation affords our species widespread protection from pathogens in general—even if one person is particularly susceptible to a certain viral infection, for example, the likelihood of everyone being susceptible to this virus is made extremely low by our extraordinary genetic diversity. This diversity is afforded by sexual selection that allows humans to acquire new traits with every generation.

Yet there is sex. Most animals and plants reproduce that way. Experts now believe that parasites are the reason for having sex. Contrary to disadvantages of sex, created are conditions in which it is desirable to “mix” genetic material because the newly obtained offspring with new genetic combinations are potentially superior to the old ones to combat parasites.

There’s no guarantee that newly acquired traits will be useful, and many of them can be neutral, like eye color, or detrimental, like genetic diseases. Over evolutionary time, however, sexual reproduction is hypothesized to give organisms a leg up in the arms race with pathogens. So in addition to allowing you to make babies and enjoy yourself at the same time, sex may also play an important role in protecting species from extinction.