You can assume. But can you put it to fruition?
To be an end in yourself, you have to know first that you exist. To perceive your own existence you need some kind of feedback. No other thing or creature, but another human being can reflect back on you.

Why would you build a house if there's no one there to inhabit it? You could very well be writing books that no one would read, or staging plays that nobody would see. It's useless when you don't keep other people in mind while doing that. If you are an end in yourself, then your birth and death are, as well as your life. You just live and consume energy for the sake of creating order that will become chaos sooner or later. If all your creations are to become chaos, what is the reason for you to create anything?
That's where you need another human being, for nothing else would appreciate your putting energy into doing something that will come to its original state in the end. This state of order, that we as human beings are trying to create, can only be appreciated by us as human beings. You need another person in your life so that your life has meaning.