Not to be adding fuel but You have to be honest with yourself-every primitive person had to "do with what they had". Not just the people in your area. Living off the land ,though may seem like a fantasy for a lot of people, is not fun and requires alot of skill and work which would kill most of us.. For someone to say this is what a sinker should look like and only this, has never walked an inch in the foot prints of any of our anchestors. If you are building a fishing net and need weights why would you spend days making a groove in a rock,when perfectl natural rocks with holes are laying around. But on the other hand if all of the rocks in you area are round, you would get tired of loosing you weights, and eventually put a groove in a rock. Anything natural that we find may have been a tool, but we can be certain of the ones that show wear or modifications to their natural forms. JMO