THE UNANSWERED QUESTION ON FRATERNAL TWIN CONCEPTION

So yesterday my young beautiful fraternal twin nieces came to visit and we literally talked about everything. Truth is, the last time I saw them, the only tangible thing they could say then was to request for toy gifts. But this time around we actually had a meaningful chit-chat. Flora which happens to be my favorite amongst the twin sisters kept narrating how on numerous occasions Selene could have paid for her crimes if they were to be identical twin.

Honestly, I thought I could sincerely answer all their questions, not until Selene dropped the main gist. In her words, she said, "uncle, our basis science tutor taught us that a woman normally releases one matured egg from an ovary monthly. But when he got to cases of multiple births, he said that for individuals like me and Flora to be born, two eggs must be released at the same time. Now uncle, if the release of one egg is considered to be normal, don't you think fraternal twin conception is abnormal?"

Well. I can't exactly tell how many minutes that question kept me speechless. Actually, it's not as if I was thinking of the possible ways I could answer the question. But the reason for the silence was mainly because in this part of the world "I don't know" especially from an elderly person is seen as a hideous crime. I just had to save myself somehow from the shame. My response was, "hey, lets go get some ice cream then I'll answer your question after that". Please don't ask me if I finally answered the question because I didn't. Ice cream has a way of making kids forget things. You didn't hear that from me.

Although I couldn't answer the question, I had to do a quick research on fraternal twin conception after my nieces left. Hence, the main aim of this article is to first analyze the validity of my nieces' question. I'm positive that this will go a long way in helping us draw a logical conclusion on this subject matter, and also reach some level of enlightenment which is the paramount objective of #steemstem. So, to really understand this concept, it's pertinent to start with the basis.

The birth of a new life

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(License: Public Domain: Flickr

In humans, life is considered to begin with two very tiny things. Come on; I'm not guilty of whatsoever comes into your mind because the 'tiny things' I'm referring to are sex cells (gametes). So on that note, I guess it's logical to say that without these sex cells, there's no life.

From the basic knowledge of reproduction, you'll agree with me that for a new life to be formed, the sex cells must be donated by the male and female individuals. The one that comes from the male is called sperm, while the other from the female is called egg or ovum. Funny enough, for so many people, the whole processes these sex cells go through does not matter as long as conception takes place.

On the other hand, before conception or fertilization happen, there must be heterosexual intercourse. Ejaculation which most times occur during the most pleasurable moment of this activity has to do with the male ejecting the sperms with great force into the cervix and upper part of the vagina. Thus, it might interest you to know that the involuntary contraction of the cervix, uterus, and oviduct is what aids the upward movement of these sperms. Apparently, it is through this process that a sperm is introduced to the ovum at the upper part of the oviduct.

Also, since one mature ovum is released by the female monthly (just like my niece stated), any sperm that comes in contact with it on its way down the oviduct triggers conception. Actually, how the sperm is able to fertilize the ovum is that it secretes its acrosomal enzyme which is lytic in nature thereby causing the follicle cells that surrounded the ovum to dissolve. Immediately after the sperm passes through the follicle cells, it penetrates the zona pellucida and alters the conformation of the ovum. By this means, no other sperm cell is able to fertilize the same ovum. Similarly, considering the fact that an ovum is fertilized, it's normal for one baby to be born at the end of each pregnancy. However, in some cases, nature has made it possible for multiple births to occur occasionally.

What you should know about multiple births

Quite unlike how people viewed it decades ago in this part of Africa, you should know that multiple births are not a curse in any way, And just as the name implies, multiple birth has to do with production of more than one offspring in the same pregnancy. As a matter of fact, the number of offspring produced may be two (twins), three (triplets), four (quadruplets), etc, depending on certain factors. That notwithstanding, cases of twins happens to be the commonest of them all.

The determining factor(s) of multiple births basically revolves around the woman. As earlier stated, once the sperm bumps into a matured ovum released by the ovary, fertilization takes place leading to the formation of a zygote. Since the zygote is formed at the oviduct, it continues to move down until it gets to the uterus where it implants itself. At the uterus, the zygote which initially started off as a cell (that is after the male and female gametes must have united) gradually becomes an embryo.

All the same, in few cases of multiple births, once the matured ovum is fertilized by the sperm, it splits into two identical cells which normally develop into respective embryos. Despite the fact that two separate embryos are formed, however, both of them share the same placenta till birth. Because these babies were formed from a zygote, they are known as identical or monozygotic twins. The unique thing about identical twin is that they are always of the same sex and possesses the same inherited characteristics.

However, this whole thing is quite different in cases of fraternal twins. Before fraternal twin conception can take place, a woman must release two eggs or ova at the same time. As we move ahead we'll find out if this is normal or not. But considering the fact that two ova are released by both ovaries, if they are also fertilized, each will develop into an embryo with its own placenta. Unlike identical twins that are formed from a zygote, fraternal twins develop from two different zygotes and are known as dizygotic twins. Scientific researches has proven that fraternal twins are just like any other children in the family, except for the fact that they just happen to have been conceived in the same month and also shared their mother's uterus during the same pregnancy. As a matter of fact, they could both be of the same gender or opposite. Likewise, although it's hard to spot the difference immediately after birth, fraternal twins do not look alike.

Now lets reach a conclusion

As I already said in the introductory part of this article, before we can arrive at a conclusion, we must first analyze if my nieces' question is valid or not. From the above explanation, it's agreeable that the release of one egg or an ovum is considered to be normal. However, contract to what my niece asserted, the release of two eggs or ova is definitely not abnormal. This is because some females have increased tendency of hyper-ovulation. So instead of one side of the ovary to release one matured ovum, both sides are stimulated at the same time. This results in the release of two eggs, and luckily if both of them are fertilized in the process, fraternal twins would be given birth to.

Furthermore, aside from hyper-ovulation which happens to be a genetic trait, scientific research has it that diet also plays a role in fraternal twin conception. It might interest you to know that high intake of yam containing natural phytoestrogen helps in the stimulation of the ovaries thereby triggering the release of eggs (from both sides). This is the major reason why this part of the world (Yoruba people) has the highest rate of fraternal twinning. So at this point, you'll agree with me that fraternal twin conception is entirely normal.

For further reading...

Fraternal twin conception Retrieved on the 20th August, 2018
11 Facts about fraternal twins Retrieved on the 20th August, 2018

Ramalingam, S. (2011). Modern Biology, 6th Edition. Nigeria: Africana First Publishers Plc, pp. 487-490

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