One of the generally accepted and wordwidely recognized reasons for marriage is proliferation. Although some couples might exclude this factor as part of their own reasons for getting married, the fact still remains that a large percentage of married people include having kids as one of the reasons, if not the main reason, of getting married. In Africa and especially in Nigeria, the percentage is even larger.

In certain cultures, the most familiar one to me being African, the male children held in higher esteem and considered more valuable than the female children. In some extreme cases, female children are not eligible to inherit their father's properties except they are lucky enough to have male siblings who will inherit and then decide to share some parts of the inheritance with them. Hence, it is not uncommon to see women in such cultures who are yet to give birth to, at least, a male child running helter-skelter about in search of solutions. If their husbands should die with the status quo, the family of the husbands would be the one to inherit whatever that is left of their properties. Such a terrible culture, you all would say.

Who or what determines the sex of a child?

In the culture highlighted above, society indirectly points out women as the sole determinant of the sex of the child by punishing them for giving birth to only female children. However, in reality, no one is to be blamed. The sex of a child is determined at the point of fertilization and it is strictly random events, except in some extreme cases.

Sex in humans is determined by what is referred to as the XY system. There is a pair of chromosomes out of the 23 pairs that humans have that determines whether a newly formed zygote would be a male of a female. In males, this pair of chromosome is known as XY while in females, it is known as XX. Prior to the commencement of the reproductive process involving both sexes, there is a process of gamete formation. This process ensures that the reproductive cells that will be involved in the fertilization process have half the number of genetic materials (chromosomes) of non-reproductive cells. Consequently, the sex-determining chromosomes in males become halved into X and Y cells while that of females becomes X and X cells.

^{Human gametes. Credit: quapan}

The implication of this is that there are X and Y sperms while there are only X eggs. During fertilization, both X and Y sperms in males randomly fuse with X eggs in females. If the X sperm wins the wager and fuses with X egg, a XX zygote results - a female child. If the reverse occurs and the Y sperm is the one that got lucky, an XY zygote results - a male child.

Can the fertilization process be influenced?

The tendency for humans to prefer a particular child's sex over the other has led to investigating whether the natural process of fertilization can be influenced. While several anecdotal evidence exist that the gender of a zygote can be influenced, there are no substantial scientific evidence to back up most of the claims.

Perhaps one of the strongest theories backing the claim that the sex of a zygote can be influenced is the theory by Landrum B. Shettles developed in the '60s and popular known as The Shettles method. After a series of investigations into the characteristics of the male sperms, the female eggs, and the vaginal environment leading to the cervix, Shettles arrived at the following conclusions:

1. The Y sperm prefers and swim faster in alkaline environments while the X sperm prefers and survive longer in acidic environments.
2. The vaginal environment is acidic while that of the cervix leading to the uterus is alkaline.
3. The closer a woman is to her ovulation, the more alkaline the vagina becomes.

From these conclusions, Shettle opined that in order to have a higher chance of having a male child, couples should time their sex as closer to the day of the woman's ovulation as possible and vice versa for a female child. He went further to recommend acidic or basic douching of the vagina before sexual intercourse in order to increase the chances of having a female or male child respectively.

Due to the alkaline nature of the cervix environment leading to the uterus, Shettle went further to recommend that depositing the sperm deep into the vagina towards the entrance of the cervix would improve the chances of the Y sperms winning the fertilization war and leads to the production of a male child. Depositing the semen shallowly in the vagina would, therefore, increase the likelihood of getting a female child, all other conditions remaining the same.

Contrary to the findings of Shettle, some more recent investigations have reported very limited or no differences between the X and Y sperms, except in their DNA contents. Even though the difference due to the DNA content might alter some other characteristics of the two cells, investigations are largely inconclusive.

Summary

There is no doubt that couples might prefer to have a particular gender over the other when it comes to childbearing. Preferences might sometimes be due to cultural factors that place one particular gender as being more important than the other. Biologically, only the man carries the gene - the Y chromosome - that can determine the maleness of a child. Gamete formations lead to the production of X and Y sperms in males and only X eggs in females - which sperm fertilizes the egg is a random event. However, initial research has it that the process can be influenced to favour a particular sperm depending on the timing of and position during sexual intercourse as well as a lifestyle that influences the acidity/alkalinity of the vagina. Even though there are anecdotal evidence to support these findings, later research has, however, has pronounced the assertion as inconclusive.

What is your thought?

Resources

• The Shettles Method of Sex Selection
• Can you really influence whether you conceive a boy or a girl?
• New Biological Insights on X and Y Chromosome-Bearing Spermatozoa