All animals communicate in some manner; visually, verbally, chemically, etc. Language is simply a part of animal communication. Not even all humans use verbal language due to loss of hearing, i.e. sign language. Due to all of these different types of communication, many species may not be able to communicate between them. Just as dogs and cats are unable to "tell" us where it hurts, we can't "tell" an octopus or lion where we hurt. It is not surprising that there is a human bias because we are all humans after all. Humans may possibly possess the greatest diversity of communication because we use verbal, visual, and even chemical (to the detriment of others in a subway sometimes) to interact with other people.