A campfire is a fire at a campsite that provides light and warmth, and heat for cooking. It can also serve as a beacon, and an insect and predator deterrent. Established campgrounds often provide a stone or steel fire ring for safety. Campfires are a popular feature of camping. At summer camps, the word campfire often refers to an event (ceremony, get together, etc.) at which there is a fire. Some camps refer to the fire itself as a campfire. A campfire is a fire at a campsite that provides light and warmth, and heat for cooking. It can also serve as a beacon, and an insect and predator deterrent. Established campgrounds often provide a stone or steel fire ring for safety. Campfires are a popular feature of camping. At summer camps, the word campfire often refers to an event (ceremony, get together, etc.) at which there is a fire. Some camps refer to the fire itself as a campfire. A new analysis of burned antelope bones from caves in Swartkrans, South Africa, confirms that Australopithecus robustus and Homo erectus built campfires roughly 1.6 million years ago. Nearby evidence within Wonderwerk Cave, at the edge of the Kalahari Desert, has been called the oldest known controlled fire. Microscopic analysis of plant ash and charred bone fragments suggests that materials in the cave were not heated above about 1,300 °F (704 °C). This is consistent with preliminary findings that the fires burned grasses, brush, and leaves. Such fuel would not produce hotter flames. The data suggests humans were cooking prey by campfire as far back as the first appearance of Homo erectus 1.9 million years ago. Ideally, campfires should be made in a fire ring. If a fire ring is not available, a temporary fire site may be constructed. Bare rock or unvegetated ground is ideal for a fire site. Alternatively, turf may be cut away to form a bare area and carefully replaced after the fire has cooled to minimize damage. Another way is to cover the ground with sand, or other soil mostly free of flammable organic material, to a depth of a few inches. A ring of rocks is sometimes constructed around a fire. Fire rings, however, do not fully protect material on the ground from catching fire. Flying embers are still a threat, and the fire ring may become hot enough to ignite material in contact with it, or the rocks could crack.