In medicine, a lot of animal products (hormones, surfactant) are viable treatments for people deficient in those products. This has been known for some time.
If God / Nature endowed man and animals (as if those two things are different) with similar pituitaries, adrenals, pancreas, livers, why do we think the brains are so radically different? If their adrenals make epinephrine like ours, why do we assume their brains don't produce thoughts and feelings like ours?
I think it's guilt. We're a moral animal, so we have to lie to ourselves to excuse our bad behavior: see victim-blaming ("She was asking for it"), or calling victims of injustice sub-human (Nazis called Jews "rats," America considered its slaves 3/5 of a person).
I hope some day we can transcend some of the uglier aspects of our nature. Namely, I'd like to see all the mass delusions gone. Isn't it better to know the truth? Sometimes I think the only obstruction between the truth and mankind is all of the biases we're programmed to deploy for self-preservation, the art of self-deception.