肯尼亚发现已知最早人类手斧

Archaeologists working in northwestern Kenya have found a skillfully hand-crafted stone ax which appears to have been made nearly 1.75 million years ago, making it the oldest such tool ever discovered.

The find suggests modern humans got an earlier start at sophisticated tool-making than previously believed.

The collection of tools and other artifacts that includes the hand-ax was discovered by a French team in the 1990s at a site near Kenya’s Lake Turkana. That is less than 10 kilometers from where archaeologists found the earliest complete skeleton of Homo erectus in 1984.

Geologist Christopher Lepre, of Columbia University’s Lamont-Doherty Earth Observatory, was part of the team that dated the hand-ax using a high tech method called magnetic stratigraphy.

He says that Homo erectus – who lived between 1.8 and 1.3 million years ago - had a larger brain than Homo habilis, his evolutionary predecessor.

Lamont-Doherty Earth Observatory

“So the inference we make is that Homo erectus was a smarter critter as compared to Homo habilis,” says Lepre.  

According to Lepre, the tools Homo erectus made, called Acheulean tools, were far more sophisticated than those devised by Homo habilis. Those so-called “Oldewan” tools were stone flakes and chippers, that had been bashed together to create a fairly sharp edge, but had no style.

“I would argue that once you have the Acheulean hand-ax come on the scene it is definitely indicative of a human ancestor who had the ability to imagine the shape and size of an object in their head and reproduce that object with esthetic qualities," Lepre says. "Hence you get this hand-ax, this symmetrical, beautifully made type of stone tool which is in stark contrast to the more haphazardly made Oldewan, for example.”  

Lepre says this hand-ax could be at least 300,000 years older than any other known Acheulean tools. That suggests that the human skill and foresight necessary to make such a tool is more ancient than previously believed.

For many archaeologists, that implies that other human developments, such as nuclear families, the division of labor into hunting and gathering, and the telling of stories around a campfire may also be more ancient. All these activities could be called “culture.” But Lepre warns that doing so is controversial.                

“Because those lines of evidence we don’t have directly from the archeological record. But there is a group of archaeologists who would argue those sorts of things, and would say that once you start having the formation of these very stylistic hand-axes, you are probably getting into culture proper - that is, ideas, beliefs, wisdom, if you will, that are handed down from one generation to the next.”

While technology can pinpoint the age of this hand-ax, there is no way to be certain how it was actually used. Lepre says the ax is too heavy to throw far with much force, and not sharp enough to pierce an animal’s skin, so it probably was not used for killing prey. He says the hand-ax may have been a scavenging tool.     

“Meaning that when you find a carcass on the landscape, let’s say a zebra carcass or a gazelle or a giraffe or something like that that’s been already been hunted by a lion or a group of hyenas, and you have a band of Homo erectus come along and they scare it off, they scare the lion or the hyenas off, and they grab pieces of the carcass there. So they might grab a limb bone or they might grab some ribs. Or perhaps they take one of these hand-axes and they hack off a limb and then they truck that limb to this campfire scene and they begin using the hand-ax to scrape the flesh off, or perhaps bash open the bones to get at the nutritious marrow inside.”

The hand-ax and other tools now reside with other Acheulean artifacts at the National Museum of Kenya. Meanwhile, researchers continue to excavate in the Lake Turkana area.

They are especially interested in sites whose soil layers date back at least two million years. That's where they hope to find more Oldewan tools and learn more about the relationship between Homo habilis and Homo erectus.