Visible crew/equipment: When the astronauts are running down a dusty hill in the desert, you can spot the shadow of the camera on the back of Landon and Dodge. (00:15:50)
Visible crew/equipment: Right before Taylor gives the female ape (Zira) the piece of paper with his name on it, while he is fighting the other ape, the shadow of the camera is seen on the bottom of the cage. (00:47:05)
Visible crew/equipment: After Taylor flees the market, he enters a museum and begins to run down a spiral staircase. As he reaches the bottom of the staircase, to the right of shot, a cameraman's shadow is visible on one of the carvings and the staircase's support column. (00:55:30)
Visible crew/equipment: After Taylor exits the museum he is whipped by an ape on a horse. Taylor/Charlton Heston is replaced by a noticeable stunt. (00:58:57)
Visible crew/equipment: When Zira locks Nova in Taylor's cell watch the left iron bar and you'll see the shadow of the camera approaching.
Chosen answer: Dr. Zaius did know the true history of man and ape, but he deliberately hid the truth from the other apes. For Zaius (and other high-ranking apes who were guarding the secret), it would be shameful and demoralizing to ever admit that humans were far superior to apes in the past and that they could, potentially, conquer the apes. In more than one scene (such as the paper airplane scene in the first film), we see Zaius obviously frustrated that Taylor's very existence threatens to expose the truth.
Charles Austin Miller