According to Southern Baptists, where does a baby's soul come from?

When someone dies their soul either goes to heaven or to hell, there is no true end for a soul, only for the body because energy cannot be created or destroyed. By the same token, when someone is born their soul couldn't have been created, therefore the soul must have already existed? At some point in the development of a baby, the ensoulment happens. When exactly this happens is not a universally-agreed-upon thing and may in fact be considered a controversial topic due to the atmosphere around abortions. This entire subject is completely out of the topic of this question. My question is simply, where does a new human being's soul come from, since it can't have been created? Since Christianity does not follow the idea of reusing souls, i.e. reincarnation, and souls cannot be created or destroyed, where do "new" souls come from? Concerning denominations, I am interested in hearing for all, but since one needs to focus on one, I would prefer Southern Baptist.