Biologists have found that women can choose a partner for mating, even after it has already occurred. The fact that the sperm reacted differently to the surrounding of the egg fluid, taken from different women — some are actively seeking, and some ignored. This means that egg cells selectively attract the sperm, and this choice does not depend on their own female desire. However, it is unclear what mechanism is responsible for the intelligibility and does it impact ultimately on the viability of children. A study published in the journal Proceedings of the Royal Society B.
The choice of sexual partner in many animals is not limited to external courtship. Even if the male was able to mate with the female, pregnancy still may not occur. Tools for such a choice (cryptic female choice) there are many: the female is able to throw away part of the sperm from the genital tract, to limit her mobility or may even limit the survival of the offspring within the uterus. However, most of these mechanisms are known for other mammals but not to humans. However, there is no reason to think that people have no hidden mechanisms of choice, and even have a suspicion that it is responsible for the non-equilibrium distribution of the sexes in the population — people on average, boys are born slightly more often than girls.
It is known that human eggs are able to guide the movement of the sperm to his side. A group of scientists under the leadership of Daniel Bryson (Daniel Brison) from the University of Manchester set out to test whether they are able to choose from these sperm suitable for yourself. For this, the researchers turned to a clinic that deals with in vitro fertilization, and obtained from her samples of sperm and follicular fluid (that surrounds the egg inside of the ovary and stored for some time after ovulation).
Then the authors suggested that the sperm “choice”: in a Petri dish were immersed two capillary to the follicular fluid and started the sperm, and then estimated the number of cells, that float on the capillary. The more, the follicular fluid is intriguing. In different experiments the sperm is offered to “choose” between follicular fluid of “their” or “alien” partner, or between the follicle fluid and the control solution.
The researchers found that, regardless of the design of the experiment is to select between two liquids or turns between one and the solution is one of follicular fluid was often more attractive than the other (p < 0.001). While it might not be the fluid of the partner, which chose the owner of the sperm to “their” liquid went 516 the average of sperm per hour, and the “alien” — 442 (p = 0,77, so the difference can be considered insignificant).
At the same time, the speed of sperm in the capillary did not differ depending on to whom they are committed (p > 0.05). This means that the movement of the sperm really depends on the fault-finding eggs, not from non-specific factors like the viscosity of the medium. However, the particular mechanism which is used for egg discrimination of sperm is still unclear. The researchers suggest that it may be associated with genetic compatibility, but this theory remains controversial.
In animals, the mechanisms of the hidden choice is usually increase the survival of offspring. In this experiment, nothing of the kind could not be found: regardless of, turned to the sperm attractive the same partner as for the owner, or other, all pairs with the same probability occurred fertilization (p = 0,6), get high-quality embryos (p = 0,26) women became pregnant (p = 0,42) and appeared children (p = 0,18).
However, the authors note that this may be the cost selection. Because all couples had to resort to assisted reproductive technologies, this means that, on the one hand, they will be less compatible than the average pair in the population, and on the other hand, meeting their reproductive cells significantly facilitated. This means that people who conceive a child naturally, hidden choices can still affect the viability of the offspring — but check and confirm it will be technically difficult.
Previously, we wrote about the fact that people have not found the propensity to give birth to only boys or only girls, but found the effects of selective abortion, which cost the world at least 23 million girls. In addition, Japanese scientists have found a way to selectively inhibit sperm “female”, which could theoretically allow people to choose the gender of your child before conception.