Imagine that all the humanoid and demi-human laguages are actually the same, but pronounced with outrageous accents and bizarre idiom. All the elves have a French accent, all the Dwarves have Swedish, Dragons have a Pakistani accent...
As population increases, animal souls are promoted to human before they are spiritually advanced enough in terms of impulse control, etc.: this shouldn't have happened, but karmic progression is automatic, after all--it's a force of nature. But the 'animalization' of humankind bodes ill for civilization.
No doubt the same goes for elves, dwarves, and so on.