New research suggests that ancient humans fashioned hand axes, picks and cleavers much earlier than was formerly believed - though they did not take the stone tools along when they left Africa.
Newly discovered hand axes from 1.76 million years ago are the oldest examples of the complex Acheulean culture. The tools are 350,000 years older than the previous record holders and could affect what we know about human's departure from Africa.
An international team from the United States and France made the findings after traveling to an archeological site located in the northwest shoreline of Kenya's Lake Turkana - the location of the Turkana Boy discovery (a Homo erectus skeleton found in 1984 that is considered the most complete skeleton of a prehistoric man).
Large cutting tools and two-faced blades had previously been excavated at the site, however, using the sophisticated paleomagnetic technique to date the dirt, researchers calculated the age of the advanced tools to be 1.76 million years old.
Similar stone-age artifacts in Tanzania and Ethiopia are estimated to be between 1.4 and 1.6 million years old.
Paleomagnetic dating takes advantage of the flip-flop of Earth's magnetic field every several hundred thousand years to come up with a fairly specific estimate.
Finding tools whose shapes required a planned design and specialized execution suggests that prehistoric humans created refined tools that required a high level of thinking much earlier than previously thought.
Though no Homo erectus fossils were found with the Turkana tools, a skull of the early human was excavated last year in the same sediment level across the lake, suggesting that Homo erectus was responsible for these particular tools.
Anthropologists consider the Acheulean hand axes to be the culture of our ancestor Homo erectus, and we know H. erectus first evolved around 1.8 or 2 million years ago, study researcher Christopher Lepre, of Columbia University, told LiveScience. I think most researchers were anticipating that older stone axes would be found.
Now they've found them.
While the team found several crude stone flake tools from an older culture, the Odowan culture, the presence of highly defined teardrop or oval shapes of the Acheulean hand axes show a much higher level of thinking in the mind of Homo erectus.
The data indicates that there were at least two tool-using hominoids living in Africa 1.76 million years ago - Homo habilis, likely using the Odowan tools, and Homo erectus using axes that were suited for chopping wood or butchering animals.
Homo erectus is considered to be the first to fan out in great numbers from Africa. While they walked upright like modern humans, they possessed a flat skull, sloping forehead, and a smaller brain.
Herein lies the lingering question: If Homo erectus created these tools in Africa, why are none present in the earliest sites in Asia and Europe?
Some argue that early humans could not find the raw materials in their new surroundings and lost the technology through the generations. Others argue that, once out of Africa, early humans didn't need the advanced technology because there was less competition. Some say the group of Homo erectus that migrated to Europe may not have developed the Acheulean technologies yet.
While the mystery remains, the study definitively proves that early humans used fine-crafted tools much earlier than we thought.
Results of the study appear in Thursday's issue of the journal Nature.