I always look forward to reading your posts, @zest. In my discipline of study we deal with something called the personhood argument, wherein a movement is growing which suggests that some humans are less "persons" than some animals. The argument is based upon self-awareness, and leads to the conclusion that a living human could cease to be a person. In the context of addressing that argument, I really appreciate your observation that the use of symbols is a distinguishing feature between humans from animals.