other activities required tools such as preparing food, "...nutting, leatherworking, grain harvesting and woodworking..." Included in this group are "flake stone tools". Tools are the most important items that the ancient humans used to climb to the top of the food chain; by inventing tools, they were able to accomplish tasks that human bodies could not, such as using a spear or bow to kill prey, since their teeth were not sharp enough to pierce many animals' skins. “Man the hunter” as the catalyst for Hominin change has been questioned. Based on marks on the bones at archaeological sites, it is now more evident that pre-humans were scavenging off of other predators' carcasses rather than killing their own food. Timeline of ancient tool development Many tools were made in prehistory or in the early centuries of recorded history, but archaeological evidence can provide dates of development and use. Olduvai stone technology (Oldowan) 2.5 million years ago (scrapers; to butcher dead animals) Huts, 2 million years ago. Acheulean stone technology 1.6 million years ago (hand axe) Fire creation and manipulation, used since the Paleolithic, possibly by Homo erectus as early as 1.5 Million years ago Boats, 900,000 years ago. Cooking, 500,000 years ago. Javelins, 400,000 years ago. Glue, 200,000 years ago. Clothing possibly 170,000 years ago. Stone tools, used by Homo floresiensis, possibly 100,000 years ago. Harpoons, 90,000 years ago. Bow and arrows, 70,000–60,000 years ago. Sewing needles, 60,000 - 50,000 BC Flutes, 43,000 years ago. Fishing nets, 43,000 years ago. Ropes, 40,000 years ago. Ceramics c. 25,000 BC Fishing hooks, C. 23,000 years ago. Domestication of animals, c. 15,000 BC Sling (weapon) c. 9th millennium BC Microliths c. 9th millennium BC Brick used for construction in the Middle East c. 6000 BC Agriculture and Plough c. 4000 BC Wheel c. 4000 BC Gnomon c. 4000 BC Writing systems c. 3500 BC Copper c. 3200 BC Bronze c. 2500 BC Salt c. 2500 BC Chariot c. 2000 BC Iron c. 1500 BC Sundial c. 800 BC Glass ca. 500 BC Catapult c. 400 BC Cast iron c. 400 BC Horseshoe c. 300 BC Stirrup first few centuries AD Several of the six classic simple machines (wheel and axle, lever, pulley, inclined plane, wedge, and screw) were invented in Mesopotamia. The wheel and axle mechanism first appeared with the potter's wheel, invented in what is now Iraq during the 5th millennium BC.