There are a number of things to do in the valley so you should explore fully, collecting all the inventory items scattered about. Arok's first thoughts on exiting the caves are of hunger pains, so finding food is a priority.
I've included a map of the valley that also details all the inventory items needed and where they can be found.




From one location along the river bank (4 on the map) you can see the fish swimming. Conveniently, a harpoon point has been left on the rocks. Take the harpoon point to the 'combining rock' and attach the shaft to it with the strap.
Harpoon in hand, return to the river bank and test your fishing skills. After a few unsuccessful attempts at harpooning a fish Arok realizes the fish are swimming too fast. Can you think of a way to slow them down? Watch the route taken by the fish closely and note that they always swim between the rocks in the river. Perhaps you can slow them down by narrowing the gap between the rocks. The four loose rocks (two on either side of you) can be used. You have to first add the largest rock (extreme left) followed by the next largest (nearest on your right) and finally the two smaller ones. The fish will now temporarily stall at the rocks, allowing you to harpoon one of them quite easily.
Sushi was not popular in Arok's time, so the next task is to cook your prize catch.


You find Toar, the flintknapper, at the burnt out fire. Talk to him and get some marcasite and a wooden recipient from him. Use the branches, tinder and marcasite to build a fire, then light it by using the knapped flint on the marcasite.
You can't simply put the fish in the fire, but must grill it on the large rock to the left of the fire. The rock is obviously cold and needs to be heated. Use the wooden stick in front of the fire to push the large rock onto the fire. Wait a while and then remove the rock, again using the stick. Grill the salmon (not forgetting to turn it over to cook both sides) and then give it to Toar.
From the documentary database you know that liquids are boiled by inserting heated stones. First, you need to fill the wooden recipient with water at the same spot you caught a fish. Place the filled wooden recipient just in front of Toar. Using the wooden stick put the three small stones (on your right) into the fire, then remove them (using the stick) when they're hot enough. You have to endure burning your fingers trying to pick up the hot stones before Toar gives you the wooden spatula. Use it to drop the three stones into the filled wooden recipient and then add the camomile.


In appreciation for the meal Toar gives you a lesson in flint knapping. The tools are numbered 1, 2, 3 (in the diagram) and the flints are A, B and C. Note that after picking up and replacing one of the tools, descriptions of all the tools are displayed when the cursor hovers over them.

You won't have much success with flints A or C, but B is ideal for knapping. Use the stone hammer (3) three times to chip the flakes off B, then refine it by using the reindeer antler hammer (1) twice. When done, take the core from your inventory and give it to Toar. He adds the finishing touches and hands you a knife.


You need to have picked up at least one of the four worked stones in the area to activate the topic with Toar. Ask him about the stones and he gives you the fifth one and a bone to use with them.
Toar tells you that the painted signs are a 'guide' to getting to the cave dwelling above. The only symbols that  you are able to interact with are those on the rocks at (9) on the map. Note that you must have all five stones to do this.
Although the stones produce different musical notes when struck with the bone, this has nothing to do with solving the puzzle. Each time a stone is struck one of the symbols reacts by changing colour.

Strike each stone four times noting the reaction of the symbols.  In sequence (A, B, C, D) each symbol will either turn black or a reddish brown. Test all five stones to establish the colour pattern for each.
Note that the bisons above the symbols are the same reddish colour as that of the symbols, obviously the key to what must be done with the symbols - all four must be red. The first note from stone 4 turns A to red, the second note from stone 2 turns B to red, the third note from stone 5 turns C to red and the fourth note from stone 1 turns D to red. Strike the stones in that order (4 2 5 1) to activate the cave entrance to Tika's dwelling.