Letter from Charles Darwin to Asa Gray (22nd May 1860)
With respect to the theological view of the question; this is always painful to me.— I am bewildered.— I had no intention to write atheistically. But I own that I cannot see, as plainly as others do, & as I shd wish to do, evidence of design & beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidæ with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice.
On that note, what's up with the obligate coprophagy of the koala? And their famously smooth brains? I'd make the koala, were it I in the high seat, but a kind and caring creator wouldn't.
Some herbivores can't digest their food all the way, cows get around it by having more than one stomach and also chewing their cud (vomiting up from first stomach and rechewing). Rabbits do the same thing as koalas, partially digest their food and eat their poop.