Can we truely say this?

[Anonymous]

I was working on my astronomy packet in physics. I had to take notes from websites that talked about different facts about the planets, Sun, and Moon. In several places it said "(Such-and-such planet) has been known since prehistoric times."

My question is: how can we truely say that a planet, or anything for that matter, has truely been known since prehistoric times. To me, prehistorc means pre-written history. Some of you may be thinking that there may be cave paintings that depicted Mars or Venus, but a cave painting could be considered a form of written (and pre-oral) history.

What do you think of this? Does this make any sense to you? I'd be interested to hear your imput on this.