Using tools has been interpreted as a sign of intelligence, and it has been theorized that tool use may have stimulated certain aspects of human evolution-most notably the continued expansion of the human brain. Paleontology has yet to explain the expansion of this organ over millions of years despite being extremely demanding in terms of energy consumption.
The brain of a modern human consumes about 20 Watts (400 kilocalories per day), which is one fifth of the energy consumption of a human body. Increased tool use would allow for hunting and consuming meat, which is more energy-rich than plants. Researchers have suggested that early hominids were thus under evolutionary pressure to increase their capacity to create and use tools.
Precisely when early humans started to use tools is difficult to determine, because the more primitive these tools are (for example, sharp-edged stones) the more difficult it is to decide whether they are natural objects or human artifacts. There is some evidence that the australopithecines (4 mya) may have used broken bones as tools, but this is debated. It should be noted that many species make and use tools, but it is the human species that dominates the areas of making and using more complex tools.
A good question is, what species made and used the first tools? The oldest known tools are the “Oldowan stone tools” from Ethiopia. It was discovered that these tools are from 2. 5 to 2. 6 million years old, which predates the earliest known “Homo” species. There is no known evidence that any “Homo” specimens appeared by 2. 5 million years ago. A Homo fossil was found near some Oldowan tools, and its age was noted at 2. 3 million years old, suggesting that maybe the Homo species did indeed create and use these tools. It is surely possible, but not solid evidence.
Bernard Wood noted that “Paranthropus” coexisted with the early Homo species in the area of the “Oldowan Industrial Complex” over roughly the same span of time. Although there is no direct evidence that points to Paranthropus as the tool makers, their anatomy lends to indirect evidence of their capabilities in this area. Most paleoanthropologists agree that the early “Homo” species were indeed responsible for most of the Oldowan tools found. They argue that when most of the Oldowan tools were found in association with human fossils, Homo was always present, but Paranthropus was not.
In 1994, Randall Susman used the anatomy of opposable thumbs as the basis for his argument that both the Homo and Paranthropus species were toolmakers. He compared bones and muscles of human and chimpanzee thumbs, finding that humans have 3 muscles that chimps lack. Humans also have thicker metacarpals with broader heads, making the human hand more successful at precision grasping than the chimpanzee hand. Susman defended that modern anatomy of the human thumb is an evolutionary response to the requirements associated with making and handling tools and that both species were indeed toolmakers.
Stone tools are first attested around 2. 6 million years ago, when H. habilis in Eastern Africa used so-called pebble tools, choppers made out of round pebbles that had been split by simple strikes. This marks the beginning of the Paleolithic, or Old Stone Age; its end is taken to be the end of the last Ice Age, around 10,000 years ago. The Paleolithic is subdivided into the Lower Paleolithic (Early Stone Age, ending around 350,000-300,000 years ago), the Middle Paleolithic (Middle Stone Age, until 50,000-30,000 years ago), and the Upper Paleolithic.
The period from 700,000-300,000 years ago is also known as the Acheulean, when H. rgaster (or erectus) made large stone hand-axes out of flint and quartzite, at first quite rough (Early Acheulian), later “retouched” by additional, more subtle strikes at the sides of the flakes. After 350,000 BP (Before Present) the more refined so-called Levallois technique was developed. It consisted of a series of consecutive strikes, by which scrapers, slicers (“racloirs”), needles, and flattened needles were made. Finally, after about 50,000 BP, ever more refined and specialized flint tools were made by the Neanderthals and the immigrant Cro-Magnons (knives, blades, skimmers).