All sorts of animals can communicate, but no other animal can speak. They can't have conversations, explain ideas or describe their emotions.
But man (and man alone) possesses language; a tool which enables him to move beyond mere communication into a world of sophisticated relationships, abstract ideas and a purpose driven life.
Many animals are clever, but none of them are brilliant. They don't compose symphonies, construct space stations, or discover the laws of physics.
But man does all of this and more. He wonders, considers, thinks, solves problems and plans ahead; it is all part and parcel of a rich mental world that belongs to man and man alone.
Man's intellect is powerful, but can't do much on its own. In order to put man's brain to use he needs a physical body that can take advantage of his intellect.
And it just so happens that man possesses a body which is able (among other things) to construct and utilized the tools needed to transform his mental world into physical reality.
When a lion see a sunset he thinks dinner. When man sees a sunset he's struck by its beauty. When a bird hears music he may dance, but only man is emotionally moved.
Man alone seems to experience and wonder about the world in a meaningful way. Only he experiences lofty & spiritual emotions and wonders why he is here.