Comment: I am so glad you brought that up

Dogs are a good example of adaptation, take a black lab, they are much more adapted to a water environment, short hair, webbed feet and love water, a German Shepard, long hair double coat, won't go in water at all. I tried to google that question and got two different answers, yes, dogs can dive under water a very short distance. One site said they can hold breath, and another said there is a membrane in their nose that acts like a eye lid and shuts off the voluntary breathing, so not brain controlled breathing. I don't know, but like you, open to the theory. I did find out that polar bears can hold their breath under water, but that brown and black bears can't. Morgan brings out some interesting facts supporting her thesis. Human bodies appear to me to be more similar to the aquatic mammals than the terrestrial mammals, so i would not be surprised if there was a semi aquatic or an aquatic ancestor.