So far we haven't had time to write an essay on this topic.
For now we hope it suffices to note that in 30,000 years (or 6000 years, if you prefer), of human existence on this planet, there has never been any confirmed report of animals having any civilization or culture (art, tradition, religion), or of their making or using tools or any type of symbolic language. Yes, some apes do hollow out straws and use them to suck out ants, but clearly that exception is pretty low-level, and really not so exceptional. Yes, Coco the gorilla could employ sign language, but she could not use it in any symbolic way, for example, when someone signed to her ``yesterday'' she looked backward over her shoulder (see National Geographic, January 1985).
Neurosurgeon Wilder Penfield of Princeton....performed surgery on 1,132 epileptics over a thirty-year period. After removing a part of the skull of the patient under anesthesia. he would bring him back to full consciousness. Then Penfield would explore the brain widely with an electronic probe. Since the brain lacks sensitivity, the patient, though fully alert, could feel no physical pain.
WIth the patient guiding the surgeon's explorations and reporting the results of stimuli at different cerebral sites, the doctor would often find and remove the cause of the epilepsy. In the process of pursuing this procedure with more than a thousand patients, Penfield gained a unique and voluminous body of fata on the responses of different parts of the brain to an electrical stimulus. Combining these experimental findings with extensive studies of epileptic effects--also consisting of localized electrical bombardment of regions of the brain--Penfield made many original contributions to the mapping of brain functions. But as in the case of Michelson and Morley's ether tests, more important that all his findings was a momentouis absence. Nowhere in the brain did he discover any evidence of mind: the consciously deciding, willing, imagining, and creative force in human thought.
Penfield summed up his conclusions:
The electrode can present to the patient various crude sensations. It can also cause him to turn head and eyes, ot to move limbs, or to vocalize and swallow. It may recall vivid re-experience of the part, or present to him an illusion that present experience is familiar, or that the things he sees are growing large and coming near. But he remains aloof. He passes judgement on it all. He says, ``things are growing larger'' but he does not move for fear of being run over. If the electrode moves his right hand, he does not say, ``I wanted to move it.'' He may, however, reach over with the left hand and oppose the action.