There are many reasons why we have sex, which in our view is logical and positive, but for a long time science has a different opinion.
The practice of sexual reproduction is a very expensive method not only in terms of energy produced (first production of sperm and then the transmission of sperm to the uterus of the mother and fluctuations in the uterus during pregnancy and menstruation ...) but you need two adults for the birth of one small child
This result and with a little knowledge of arithmetic is a small payoff for this process
However, researchers from the University of Stirling in their study that the mechanism of reproduction maintained by mammals through successive generations enhanced the immunity of those generations against a wide spectrum of bacteria