1) What happens when, after a couple of days of cell division, the blastocyte splits into two identical twins? Which one gets the soul? Or does the other get a new soul at the point of division - days after conception?
2) What happens in the case of a chimera? A chimera is produced when there are two separately fertilized ova (fraternal twins) in a womb and, for reasons yet not understood, they both combine into a single ovum and continue to develop as a single human being with two separate sets of DNA. A chimera can even have two separate fathers if the mother had sex with two men during a single fertile period. The chimera of two male or two female ova most likely will never know he or she is a chimera unless DNA testing reveals the two disparate sets of genes. A chimera from both a male and female ovum will usually be intersexed to one degree or another, which is a bit of a tipoff.
Given that both ova were separately ensouled at conception, what happens to the two souls when they combine? Is one soul lost or gone to Heaven? Or, does the chimera spend his or her life with two intermingled souls? Might one go to Heaven and one to Hell?
The more we learn about biology, the more we have to adjust our religious definitions. At the time the Bible was written, people had little or no understanding of the physical world around them (though one wonders why God appeared equally uninformed), and so they wrote a lot of unintentional misinformation into their religious texts.
In the fifth century BC, Hippocrates wrote:
"People think that epilepsy is divine simply because they don't have any idea what causes epilepsy. But I believe that someday we will understand what causes epilepsy, and at that moment, we will cease to believe that it's divine. And so it is with everything in the universe."
I suspect that the passionate fight between creationism and evolution (and science in general) is an attempt to hold back this process as long as possible.