Perhaps, as the conceptus is beginning to divide into two or more separate humans it receives a second soul or more.
We are certain to not agree on what a soul is. Since I do not believe it is possible to separate "consciousness" from the meaning of soul, whatever you believe a soul is, to say something has more than one soul would mean it had more than one consciousness, which is absurd.
My guess is that you would like a "scientific answer," ...
Hardly. It is not a question science can address. The consciousness is subjective, as we experience it. Science deals with the objective and demonstrable.
Since I also believe human consciousness, "qua human," does not really exist until it has reached the stage where it can (whether it does or not) rationally and volitionally develop cognition (verbal knowledge), it is not yet a human soul or consciousness. This does not deny consciousness; it does not deny "humaness," in the genetic sense; it does deny that in terms of moral and political principles, true humaness does not exist until conscious rational choice is possible.
We do not hold any creature incapable of making conscious choices morally responsible. Moral responsibility cannot be divorced from any correct concept of rights. Only those capable of responsibility have rights.
Hank
So persons with low IQs have no rights?
But, I didn't say any individual being had more than one soul.
It's common knowledge that one egg, which is fertilized by one sperm, might develop into two separate beings. I'm saying that there are two souls at the point at which there are two "beings."
Yes, it looks that way.
You have a right to define "soul" that way, but ...a lot of people think that the soul is the life force of a individual being, not the consciousness of a individual being.
According to your definition of soul, i.e., consciousness, it is absurd to think one being would have two souls.
Even according to my definition of the soul, it is absurd to think either
Soulness goes hand in hand with "beingness." Each individual being has an individual soul.
Even a twin does.
Humans have known about identical twins for years, even though they didn't understand the "nitty gritty" details involved in having one fertilized egg become two individuals. We can easily talk about two individual beings resulting from the same fertilized egg.
We can just as easily talk about each of those two, separately developing, individual, human beings having their own soul, even though they both started life as the same fertilized egg.
It's logical for those of us who think individual human beings have souls at the earliest stages of their development, to say that each individual human being, even if it is a twin, gains its own soul as soon as it begins its individual development.
After all, it makes just as much sense to say a single fertilized egg can follow down a developmental pathway which results in two souls as it makes sense to say a single fertilized egg can follow down a developmental pathway which results in two beings.
I can't pinpoint the moment at which there are two souls...but, then again, I can't pinpoint the moment at which there are two beings.