Mammals, including humans, are programmed by nature to continue their kind, and during the processes of preparation for reproduction, selection mechanisms are triggered to give future offspring the best chances of survival: physical strength, endurance, immunity. According to CNN, scientists were able to reveal another cunning secret that contributes to the birth of more successful human offspring.
From the beginning of time, the female instinctively stopped the choice on the most promising: the strong one, able to feed and protect, and even though in modern conditions these requirements have been transformed and modified, they still play decisive roles. The choice of a partner for procreation by a woman remains a test in which the unsuitable are eliminated: the weak, the sick, not persistent enough.
In addition to pre-selection, the female reproductive system itself is also a test, an obstacle course. The hormones released during ovulation largely determine the female choice, outstripping the actions of reason and feelings, and as a result, the competition ends in individuals with potentially promising genes that can give offspring survival and advancement along the evolutionary ladder.
But the competition doesn't end there. According to a new scientific study, female preferences in choosing a mate for offspring persist and appear even after sex - during the journey of sperm to fertilization. Apparently, the final decision about whose sperm will become the lucky winner is made by the egg, and she does not always "agree" with the female choice of a partner.
Such results were obtained empirically. Researchers in the UK focused on experiments with samples of follicular fluid and sperm remaining in biological material banks from 16 couples undergoing assisted reproductive treatment at St Mary's Hospital in Manchester. Scientists "shuffled" semen and follicular fluid, observing the process.
It turned out that if the egg decides that the sperm of a male is worthy of fertilization, then the chances of a new life will increase by 18-40%. In order for the miracle to happen, the follicular fluid begins to "show" the way for the sperm cells that are interested in the egg by releasing special chemicals. Sperm, as it turned out, have odor receptors in their heads, and, having “smell” the promising smell, sperm cells increase speed.
Promotional video:
Human eggs release chemicals called chemoattractants, which leave a kind of chemical trail that sperm use to find infertile eggs, explains the study's author, associate professor of zoology at Stockholm University John Fitzpatrick. “Before that, we didn't know that chemoattractants react differently to the sperm of different men, in fact, choosing which sperm will be the winner.
The idea that the eggs themselves select the sperm is really new, says Daniel Brison, senior author of the project, research director of the department of reproductive medicine at St. Mary's Hospital in the UK. “Research into the interaction of eggs and sperm will improve fertility treatments and may ultimately help us understand some of the currently unexplained causes of infertility.
According to John Fitzpatrick, about a third of all cases of clinical infertility have unexplained causes.