A new study shows that even though the fastest and most capable sperms reach the ovum first, it is the egg that has the final say on which sperm fertilizes it. W O W!
The study titled, “Chemical signals from eggs facilitate cryptic female choice in humans,” is published in the latest issue of the journal Proceedings of the Royal Society B.

There is a chemical communication that occurs between the female reproductive system that receives the sperm and the incoming sperm cells from the male partner. They explained that the primary mechanism might be known, but the molecular mechanism that forms the basis of choice of sperm cell by the egg is not clear. They write, “there is a growing appreciation that females can bias sperm use and paternity by exerting cryptic female choice for preferred males.” They looked at the effects of follicular fluid present in the female reproductive system on the incoming sperms. The team wrote that this fluid in the follicles or tubes is known to have certain chemo-attractants which attract the sperms. They used follicular fluids from the female partner and exposed the sperms to these fluids. Both partners (the male partner of the female whose follicular fluid was tested) and non-partner (another male) sperms were exposed to the follicular fluid of a female. For this study, the researchers used the follicular fluids and sperms from six couples who were undergoing treatment for infertility.

This study found that there is a MARKED differentiation between the attractions from the follicular fluid of a female partner compared to the follicular fluid of a non-partner for the sperm cells. This indicated that there is a distinct mate choice when it comes to eggs and sperms.

Choosing sperms that are compatible with the follicular fluid could help. The new study shares there may be a chemical incompatibility between the sperms and the follicular fluid that made it difficult for couples to conceive.