I believe it was in Conversations With A Spirit by Dolores Cannon (or one of her books) that I read that if the Human owner of a pet loves that pet enough, his or her pet will attain a Human Soul and be born Human in its next life. I believe the stages of life go from Plant to Animal to Human. Dolores says you cannot go from a Human Soul back to an Animal Soul or Human life back to an Animal life in the next life. You cannot go backwards.