While researching the evolution of human intelligence, Charles Darwin proposed that it evolved just as physical adaptions to acquire food, shelter, mates and basic survival. He based his theory after observing earthworms. He found that they made choices on which type of leaf use to block their tunnel. This began the awareness of the intelligence of animals.
However, it was not until 1977 when Irene Pepperberg bought an African Grey parrot from a pet store to understand animal intelligence through speech. Before her experiments, gorillas and chimpanzees where taught sign language and were able to communicate with their researchers. It was found that they could put together basic idea.
Also discovered was that some dogs could be shown a picture of a toy and retrieve that toy from another room. Elephants could paint pictures and use a stump to reach food. Octopi open jars to get treats. A chimpanzee in a Kyoto University study could recognize and remember numbers from one to nine flashed on a touch screen.
In the past Aristotle listed animals from basic to humans who he put at the highest level. Descartes felt that animals had no soul. Skinner continued this proposal in the early 20th Century.
Milwaukee area pet owners know that their animals do have souls and have no problems communicating with them. They know that they are intelligent beings.