In this level, you will come to a cave entrance with spiders surrounding a tree stump to the left. Ignore it for now, but this is the location of one lever. After you defeat the Raptors (kill them with flaming spears), light a spear on fire and burn the brush to the left of the gate while facing it. This will unveil the second lever. Grab a spear or bone, stab a dragon fly, then go back through the cave where the spiders were. Throw the bait to the right so the spiders leave the tree stump and you can obtain the other lever.