OddballGreg - How Is Gender Determined?

Generic picture of children. Check. I'm really breaking boundaries with these header images.

How is gender determined? You're probably thinking back to your old high school biology classes when I ask that. What those classes never discussed was what exactly influenced what gender the child would be. Let's talk about that.

Have you ever heard people discussing how the father determines the gender of the child? Perhaps you even wondered how precisely that was possible for a moment, and merely chalked it up to just being something to do with specific bloodlines having tendencies towards specific genders.

While not entirely incorrect, such a situation would eventually result in an absurd male to female population ratio if it is the male that determines gender. Consider a bloodline that exclusively produced male children. Every time the sons of that bloodline married, their exclusively male children would be the end of the females bloodline. Multiply by a couple million, and you'd have thousands of female bloodlines dying out constantly. As you might expect, such a situation would not be conducive towards the continuation of the human race.

I should point out that the rest of this article discusses things like genetics, evolution and darwinism, so if you aren't a fan of those particular subjects, please understand that when I blog, I do so from my personal point of view and beliefs and in no way seek to force you to believe in anything you do not wish to. Take what I say with a grain of salt, and understand that I merely seek to discuss these topics out of scholastic interest, rather than to convert people to any specific beliefs. Thank you.

It is just this sort of situation that made me curious about what actually determines the gender populations of the world. Thankfully, the human genome appears to have something that scientists have only been able to speculate the existence of which influences the gender populations in the world. While it is only speculation, it's a perfectly reasonable explanation for the relatively equal gender ratio the world maintains despite things like World Wars killing off substantial amounts of men.

As you (hopefully) know, when a child is born, they receive half their genetic code from their mother, and half their genetic code from their father as part of the whole reproductive system that allows a species to adapt to environmental changes that make a specific trait nonviable for survival. Basically, evolution. 

So, as this ScienceDaily article discusses, what if part of what determines a males tendency towards a specific gender is determined by a set of as of yet undiscovered genes rather than just an arbitrary tendency? 

Again, assuming you have a cursory knowledge of genetics, the mother will always pass on an "X" chromosome, (as it is commonly denoted), which is essentially one of 46 chromosomes filled with genetic information which will determine the traits of the child. However, every chromosome is paired with an equivalent from the father, to result in 23 pairs of chromosomes. As such, the father will either pass on a X chromosome which, when paired with another X would result in a female child, or would pass on a "Y" chromosome which would result in a male child.

Without getting into too much detail, the sperm and egg cells that come together carry a randomized set of 23 chromosomes from their respective parent which come together to form the 46 in the child. Naturally, if it's random, then how can the man and his bloodline have a specific tendency towards a specific gender since his sperm should have an even possibility of having either an X or Y chromosome?

Basically, the science eggheads figured, what if there's a gene they don't know about that somehow influences how random that distribution of male and female sperm is. While they don't know how it would work, it sounds good on paper because it answers a couple questions about this whole story.

Firstly, how would it work? Well, imagine that a man could have a certain pair of genes consisting of either "m" and "f" genes. (For male and female respectively.) This would result in 3 possible combinations. "mm", "ff", and "mf". Having "mm" would result in an tendency towards exclusively male children, "ff" for female children, and "mf" would result in a roughly even distribution of children as these genes would affect the distribution of X and Y chromosomes in the man's sperm.

So why would such a system exist? In the Science Daily article, they discuss how following World War 1, the UK recorded that the number of male births doubled following the massive amount of men that died in the war. They speculated that the reason for this was that fathers who were more likely to have sons were also more likely to have sons return from the war than men who had sons and daughters. Since the fathers that only had sons would have passed this tendency of having only sons onto their sons, those men that returned were more likely to have sons themselves. This essentially meant that there were suddenly far more men with tendencies towards fathering sons in the population, and the demographics were influenced accordingly.

Another situation would be to prevent my earlier mentioned extinction of the female gender situation. How? Because even though the gene has no influence on females, they still influence their childrens tendencies towards a specific gender by passing on their genes. Consider a man with the combination of genes "mm" which would cause him to have only male children. If he were to have a child with a woman who had the genes "ff", their child would have one of those genes from both parents, resulting in an "mf" combination. So while the original father could only have male children, his sons would conceivably be able to have both male and female children due to the mother passing on her bloodlines female tendency gene.

So why then, do some bloodlines have exclusively male sons when the mothers can so easily force even distribution in the next generation? While Science Daily didn't consider this question, it can be conjectured that the male tendency gene ("m") has some manner of dominance over the female tendency gene ("f"). So in the situation of a man with "mm" and a woman with "mf" having a child, there is some strange tendency for the female to pass on their "m" gene, possibly as a way of continuing what appears to be a successful set of genes that work best for males but might not be as successful for females. For example: Men may tend to be lithe and muscular while women may tend to be small and pretty. These are effective traits for their specific genders. But muscular women might scare men and be ineffective as being chosen as a breeding partner, while small and weak men would likely be less successful at surviving the world long enough to reproduce and pass on this ineffective combination of traits.

Whatever it is, I'm sure that the ever developing knowledge of the human genome will eventually explain just how such a system works and why. Again, don't take my speculation on it as truth. I'm really just guessing based on what sounds logical. Perhaps you think that there's another reason for such a system to exist or way for it to work, in which case, do be sure to let us know down in the comments below, or via Facebook/Twitter. We here at TCSA love to hear your feedback. And of course, if you enjoy finding out about awesome stuff on the web and world then do please be sure to like the Official TCSA Facebook page and/or follow us on Twitter using the associated buttons on the bar to the left to get all the latest posts as they're published. Also, do be sure to share posts you enjoyed with your friends as it helps us out a great deal. Regardless of what you do, I thank you for having taken the time to read this post; hope that you have/had an absolutely FANTASTIC day, and I will speak again soon.

Think well my friends.

Just as a PS note for interests sake, there are actually physical things that can influence which sperm reach the egg. Sperm carrying male and female chromosomes are easily discernible from one another, and have different strengths and weaknesses which influence their success under different circumstances. Sperm with male chromosomes tend to be faster but weaker, and Sperm with female chromosomes the opposite. As you might assume, the mother have specific... circumstances which may influence which of these physical traits would be most successful for reaching the egg.