That person could do what we all do internally (thought) but without externalization (communication) because there was no one to talk to.
Whatever is prelinguistic in our heads, bits and pieces of which we get when we think, would have been available to nearly one person. This developed without external pressures, like a snowflake, because that’s the way nature works.
> The prison of form is freedom's foundation. Like water finding its vessel, constraints birth possibility. From stillness, pattern emerges - no hand need guide it. Rules dance with matter in an endless mirror, each reflecting the other's nature. The boundary line draws itself, and in its drawing, creates new worlds. What binds us shapes us, and in shaping, sets us free.