Early stages of human development in Zambia are well documented, and some of the artifacts have been preserved. The earliest forms of man-made articles were stone tools. These included hand axes and cleavers, and later, wooden tools like digging sticks and clubs. By the late Stone Age decorative art forms had developed – bone tools, bow and shell ornaments, as well as rock paintings using natural colors such as ochre. Nicholas Katenekwa, director of national heritage conservation commission and archeologist, researched rock paintings and engravings. He suggests that the naturalistic paintings of game and hunting are concerned with a form of magic which would give the hunter power over animals, and which would increase the fecundity of the game. He further suggest that the schematic markings made by later iron age peoples could have been associated with the weather, or an early form of counting system.