The earth is 4.5 Billion years old. I personally think that our ancestors evolved and went to other planets leaving us certain things. Now that musk wants to go to Mars we will be out of this galaxy in Hundreds of year. Then the next generation evolves etc. I saw a video of past tools they found deep in the ground. It could be what they left behind on accident? Idk that's just me. I think they don't want to tell us, but I'm on your side we are missing a huge chunk of history.