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Cell division takes place in two fundamental ways, and each occurs at just the right time and in just the right way. The first of these, meiosis, takes place during fertilization and is a form of division of the cells constituting the egg and sperm.
It is thanks to this division that human beings have the same number of chromosomes in very generation. The so-called germ cells in the ovaries and testes reduce the number of chromosomes from 46 to 23 in order to form the egg and sperm cells, respectively. When the sperm and egg combine during fertilization, the 46 chromosomes are thus completed in the embryo. But is it possible for cells themselves to make this flawless mathematical calculation? They possess such foresight and know what they must do to form a complete chromosome when they are combined. It is Allah Almighty, Who causes them to act in this way and Who establishes this immaculate system. It is revealed in one verse of the Qur'an that:
... Allah always achieves His aim. Allah has appointed a measure for all things. (Surat at-Talaq, 3)
There is great wisdom behind our Lord's involving meiosis in the emergence of a human being. For instance, the new embryo took all its chromosomes from only the mother or only the father, every zygote would still have 46 chromosomes, just like a normal human being. But there would be no human diversity on Earth. Every newborn baby would be an exact cloned copy of its mother or father. From that point of view there is enormous wisdom behind meiosis, which has been operating in a regular, flawless manner since human beings were first created. Genetic diversity is made possible by the process of DNA shuffling during germ cell division. There are so many possible combinations of DNA that the odds of two different fertilizations from the same two parents bringing two completely identical children into the world are infinitely small--approximately one in 70 trillion. 114
Prof. Gerald L. Schroeder also notes the extraordinary nature of the emergence of a human being with no abnormalities and a highly regular and attractive appearance, during the combination of genetic data:
In excess of five million combinations are possible in the complete set of traits housed within the human genome. In addition to this multiplicity, while the pairs are aligned at the equator of the cell, prior to their being pulled to opposite sides, they swap gene pieces in a process termed crossing over. Each of the two new chromosome sets now contains pieces from the mother and from the father. . . by this stage, the number of possible combinations runs into the multiples of trillions. With this vast potential for variety, it is not surprising that no two humans are identical. With all this genetic promiscuity, it's amazing that the vast majority of births produce normal-looking kids.115
We have already mentioned the dangerous consequences of errors in the DNA helix. Bearing in mind, too, that very small rearrangements in genes can also have highly negative results, the way that flawless human beings emerge from a combination of such data banks is one of the proofs of Allah's infinite might. In one verse, our Almighty Lord states that:
He is Allah–the Creator, the Maker, the Giver of Form. To Him belong the Most Beautiful Names. Everything in the heavens and Earth glorifies Him. He is the Almighty, the All-Wise. (Surat al-Hashr, 24)
The second form of cell division is mitosis, during which, the cell copies all the information contained within it, including the chromosomes, and divides into two twin cells. This progeny makes it possible for new tissues to be constructed. Thousands of heart cells are needed for the formation of the heart, for example. Stomach or kidney cells cannot replace them, so it is essential for the heart cells to multiply in order to give rise to a functioning heart. Similarly, when you cut your finger, new skin cells at the site multiply to heal the cut. In the same way, mitosis makes a baby grow during infancy and childhood. By multiplying in an ordered manner, bone cells build first the child's skeleton and then the adult one.
So important is this process that various genes carefully control the stages of mitosis. The perfection here is very striking. Two flawless cells emerge from one other cell, fully equipped to produce new cells just like themselves.
In addition, it is also most amazing that mitosis division should begin immediately after fertilization. In order for a new baby to form, cells begin dividing with an extraordinary capacity. They shape its organs, establish connections between them, and over the course of nine months, assume the appearance of a normal human being. The sublime consciousness manifested here, and each of the stages that takes place in the light of a specific aim, take place at Allah's command and under His inspiration. In the Qur'an, our Lord tells us that:
Has man ever known a point of time when he was not something worth mentioning? We created man from a mingled drop to test him, and We made him hearing and seeing. We guided him on the Way, whether he is thankful or unthankful. (Surat al-Insan, 1-3)
Say: "It is He Who brought you into being and gave you hearing, sight and hearts. What little thanks you show!" (Surat al-Mulk, 23)