"Neither steel nor stone could cause any damage, my Lord... It was simply too big, unlike any enemy we have ever seen."
Legion Captain Meron's last report to General Lorgar
"When the trees shuddered and the earth shook, we knew it was far too late to retreat."
Excerpt of General Lorgar's last report to Emperor Paulus, following the loss of his entire army of 10,000 men
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.