When do identical twins get their souls?


#1

In identical twins, there is an original organism (person) and then another develops. When would a new soul come into being? Would it not be until there was a mutation that made the second being different from the first?

Thank you.


#2

As an identical twin myself, this question has always intrigued me. To the best of my knowledge, the Church takes no official position on this matter. Catholics are free to explore different theories.

We know that human life begins at conception. The Catechism of the Catholic Church (CCC) states, “Human life must be respected and protected absolutely from the moment of conception” (CCC 2270, emphasis added). In the case of identical twins, as in the case of singletons, conception (fertilization) occurs only once therefore, each twin’s soul must exist at their shared conception.

We also know that, for some time after fertilization, embryos have the ability to generate all the cells and tissues of more than one person. In his presentation concerning cloning, Cardinal Alfonso Lopez Trujillo, states, “The totipotentiality of a cell consists in its ability to generate all the cells and tissues of a complete organism, including (if satisfactory circumstances exist) the development of an individual. In the human, each embryonic cell remains totipotent for a few days after fertilization. Homozygous germination (the phenomenon of identical twins) is the result of an incidental embryonic fission of the totipotent cells that make up the embryo in the first stages of its development” (footnote 8).

Science is presently unable to explain why “embryonic fission” (the division of an embryo resulting in identical twin embryos) occurs. It is important to consider both the cause itself as well as the timing of the cause. My identical twin brother, Jeff, and I propose the following theories:

1. At- or Pre-conception Factors: One or Two Souls May Exist at Conception
Due to presently unknown genetic or environmental factors existing prior to or at conception, the zygote (fertilized egg) is destined for embryonic fission. Therefore, when conception occurs, one of two things happens: (a) two souls exist within a single zygote, one for each embryo at embryonic fission; or (b) one soul exists, destined for “soul fission” (the division of a soul resulting in identical twin souls) - a new soul cannot come into play, as each embryo’s soul must have existed since conception, and each was conceived only once and at the same time.

2. Post-conception Factors: One Soul Exists at Conception
In this case the zygote is no different at conception than that of a singleton’s zygote because factors causing embryonic fission do not yet exist. Therefore, only one soul must exist. Later, presently unknown environmental factors cause embryonic fission and, as with theory 1(b) above, soul fission must occur.

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#3

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In these first two theories, presently unknown genetic or environmental factors are the cause of embryonic fission. Whether these factors occur (1) prior to or at conception or (2) after conception is important. If they occur prior to or at conception then the zygote is destined for embryonic fission from the start so it is possible that either one or two souls exist at conception. On the other hand, if factors causing embryonic fission do not exist until after conception then the zygote is no different at conception than that of a normal singleton zygote so only one soul, later becoming two, must exist.

In our third theory, embryonic fission relies on neither genetic nor environmental factors but, rather, divine intervention.

3. Supernatural Factors: One or Two Souls May Exist at Conception
For reasons unknown, one of two things happens: (a) one soul exists at conception but divine intervention later causes soul fission to occur which, in turn, causes embryonic fission; or (b) divine intervention at conception causes two souls to exist within one zygote and the very existence of two souls causes embryonic fission. In either case, identical twins are a miracle.


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