Cosmologists and theoretical physicists believe that if human knowledge is lost that our decendents billions of years from now may not arrive at the correct conclusion as to the age and origin of their universe.
As the universe expands, the galaxies will separate further from each other and eventually if our decendents are able to observe, because of the vast distance between galaxies, all that they will be able to detect will be the local cluster. To them, the universe will be "static" and will have no concept of the "big bang".
And on a lighter note:
"And, said Krauss, there's a positive side to not knowing the universe's true history: "There'll be almost no static on their TV screens," Krauss said, explaining that if there are no distant galaxies around to emit cosmic rays, the airways will be a lot cleaner."