Nonsense. They just don't do it as well as we do. Counterexamples to your thesis abound.
Thus, you comparison is grossly absurd. Animals have no morals, i.e. they have no sense of "ought" as humans do.
Animals have very distinct senses of right and wrong, and they make moral distinctions all the time. Spend a day at the zoo watching the elephants "aunties" taking care of, correcting and educating offspring they are unrelated to. You'd be hard-pressed to tell the difference in motivation between humans and elephants in this regard.
Furthermore, you have just stated in other words that morals are man-made.
I have not. I have stated that they are a natural evolutionary development we inherited from our ancestors, going very far back.
In that case pal, I can't be wrong!
So far, my opinion is that it would be work for you to catch up what the argument is before you could either be right or wrong.
My morals (even if my system is objective and not subjective as yours is) are, from the relativist perspective right for me, just as yours are right for you. Therefore, you don't even have a basis to argue the matter since no moral system can be wrong in your rationalist darwinian world.
This isn't has hard a problem as you are making it. Anything that's good for me but way bad for my tribe is immoral, this ain't rocket science.
I don't give a flip what natural selection says - I have a will and Natural selection is a non-entity with no moral force whatsoever - if I want to go contrary to natural selection, I can do so and many people do - they slaughter each other for no good reason.
Morality isn't automatically binding whether it's supplied by God or nature. It is just a sentimental tendency that's acute in primates, it is not a contract with reality or a force of nature, and I didn't see the nazi priests deserting their posts in the SS just because a few Jews were being slaughtered, and I didn't see Martin Luther blanching at the thought of murdering anabaptist women and children, so let's not be getting on too high a horse about this.
You said no one had demonstrated a potential source of morality other than God. Obviously, you are wrong. Morality has a keen survival value for any slow breeding social mammals, such as ourselves. If you don't like the answer, don't ask the question.
The tendency to morality from evolutionary sources is easy to see. Like many who have gone before you, you make much of the fact that the tendency is not the details of what, exactly, morality should consist of. Personally, I think that's making a mountain out of a molehill. If you want an explanation as to the source, it is the tendency in humans you are, in my opinion, asking about.
Is it tough to figure out what's moral when you don't live in the tribal mannner that spawned the tendency? You bet it is. That does not gainsay its historical sources.
If morality doesn't come from natural selection (you have just said it doesn't have to), where does it come from? Just how are humans able to make moral choices? Does free will exist? If it does, how does it exist? Is it a mere material process in the brain? Tell me, where does the sense of "ought" that we have come from?