Say what you will about 2020, but at least it’s been a good year for sperm research. We recently learned that sperm don’t actually swim, but instead torpedo through vaginal fluid like a playful little otter. Truly a game-changer for how we think about semen! Then, last week, researchers published yet another revelatory body of research pertaining to sperm — this time, though, it’s about how women’s bodies respond to it, specifically.
As it turns out, chemicals in the female reproductive system are capable of kicking some of those little otters to the curb, rejecting ones that would yield a child with lower odds of survival. Specifically, the sperm with the fewest genetic similarities to the egg are given preferential treatment, as greater genetic diversity helps offspring ward off a wider variety of infections and health issues. Unfortunately, there’s no mind-body connection to this — even if the woman’s brain doesn’t want to become pregnant, the eggs still do.
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The research, which was published in the Proceedings of the Royal Society B by scientists from the University of Eastern Finland, only utilized a pool of nine women and eight men, a relatively small study size. The women in the study were undergoing artificial insemination or in vitro fertilization, and had their cervical mucus collected for the purposes of the study. The male participants were recruited from a fertility clinic and provided sperm samples. Researchers then studied each woman’s cervical fluid in combination with each man’s sperm. Ultimately, the genotypes of both parties had a strong impact on the motility of the sperm. “Females had a stronger effect on the sperm of some males than the others,” the study says.
Because of the size of the study, the authors state that “some caution should be applied to generalize our findings and future research should ideally aim to test whether the same mechanisms are widespread in the human population” in the discussion section of the article.
So although we don’t know for sure how this information will apply to all people, it potentially overturns the lasting ideas we’ve had about how the sperm that fertilizes the egg is simply the fastest swimmer. It may be the case that not only are the sperm not technically swimming, it’s not entirely a matter of being fast, either. Instead, the sperm that reaches the egg might be the fastest of a bunch pre-selected by the cervical mucus — an indication that, even at the sperm and egg level, consent from both parties is a must.
Or, to put it another way, we still know basically nothing about the creation of human life.