There's been theorisings too, although I dont recall where exactly, that people dont possess souls per se but that they have to "grow" or develop them if they exist, it was hypothesised by some physicist who was taking into consideration debates about mind and consciousness.
I found that theory remarkable because of some of the ethical questions it gives rise to about age and stage of development, the importance of development etc. although some of those would exist in a humanistic/materialistic/reductive frame of reference too. Although what I really felt was important was that perhaps the distraction from all things spiritual and the aggressive rise of apathy, as opposed to any sort of sophisticated atheism, has meant that less people have any kind of soul to speak of and hence another explanation for the decline of supernatural incidence or experience other than the simplistic idea that modern technics and culture have dispelled it all as so much superstition.