Many lifeforms communicate. Whether it is from pheromones, like the insects (and to a smaller extent, us) to verbal language, there is some sort of communication.
Other than the opposed thumb, the thing that makes us unique is that we not only communicate, we write it down. That is a seminal difference. Here is why.
For a little background, I grew up on a farm. I heard the cows calling to their offspring, and they communicated. So it was with the cats, and the dogs, and as I became more aware, to the toads that beneficially populated our yard. They did it differently, but most had to do with mating.
The most important thing for any individual to do, other than self preservation, is to mate and thus propagate the species. To do this, some form of communication is essential.