Connectivity and social relationships help to mold and shape who we are. Things as fundamental as language, writing, tribal and communal gathering are all parts of what we think of as being human. They all involve communication, learning, observation, and interaction.
Listening to, and adding your voice to the Great Human Conversation seems to be a requirement of being part of the human race. This is a separation between being a human animal and the conscious state of humanity. With this supposition the statement indeed holds true, you cannot be human by yourself.