Ego says, HOLD IT, TIME Out!

To say that there is no other animal with the sofisticated level of intelligence and communication skills is an assumption.

Evidence shows that some primates understand symbolic representation. The gorilla Amy is one, even though she's learned it from humans.

And research also shows that dolphins can understand and relate to symbols.

The only thing we can safely say is that there are no other species that retain "human" consiousness, but we cannot say for sure that there are no kinds of consciousness that are equal to that of humans in sophistication.


A quote from Hitchhikers guide to the galaxy: (just because it's a fun quote)

"It is an important and popular fact that things are not always what they seem. For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much - the wheel, New York, wars and so on - while all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man - for precisely the same reasons."

Cyracuz

I would say it is perhaps a conjecture or theory but I would not say it is an assumption. As Popper tells us we can never prove a proposition to be true but we can only prove it to be false. If someone finds a primate that is capable of reading and discussing Hamlet with some coherence then certainly the conjecture would be proven false.

From wikipedia: (keyword "Koko (gorilla)" )

"Koko (born July 4, 1971, in San Francisco, California) is the name of a captive, acculturated gorilla trained by Dr. Francine 'Penny' Patterson and other scientists at Stanford University to allegedly communicate with more than 1,000 signs based on American Sign Language, and understand approximately 2,000 words of spoken English."

I saw a tv show about this. This gorilla had been taught the word for bracelet and the word for finger.

One day one of her trainers wasn't wearing her weddingband, and the gorilla remarked that it wasn't there. She combined the words bracelet and finger, into the word fingerbracelet.

More from wikipedia:

"However, Dr. Patterson has documented Koko inventing new signs to communicate novel thoughts. For example, she claims that nobody taught Koko the word for "ring", therefore to refer to it she combined the words "finger" and "bracelet", hence "finger bracelet"."

Since words are symbolic representations of things we see, it is reasonable to say, provided this is actually true, that this gorilla has some understanding of symbols.