Oldest hand axes found

African discoveries offer glimpse of early tool-making complexityWeb edition : Thursday, September 1st, 2011 OLD AND EDGYA stone hand ax (shown from different angles), dating to 1.76 million years ago, comes from the earliest known culture to have made such implements.P.-J. Texier, copyright MPK/WTAP

A patch of soil in East Africa has yielded the oldest known stone hand axes and picks, examples of what researchers call the Acheulian industry.

Acheulian implements unearthed at Kenya’s Kokiselei site date to 1.76 million years ago, slightly older than previous finds (SN: 1/31/09, p. 11), say geologist Christopher Lepre of Rutgers University and his colleagues. Carefully shaped, double-edged hand axes and picks lay among much simpler tools — sharp flakes pounded off stones — at Kokiselei, the scientists report in the Sept. 1 Nature.

These finds underscore suspicions that stone flakes used as chopping devices, early tools known as the Oldowan industry, did not get supplanted by hand-ax making, Lepre says. Instead, the more complex Acheulian devices emerged while Oldowan implements — which first appeared about 2.6 million years ago in the same region — were still popular, although it’s unclear how long the two types of tools were used simultaneously at Kokiselei. Hand axes and other double-edged tools typify the Acheulian industry.

Homo erectus, a possible direct ancestor of modern humans, made Acheulian tools and perhaps Oldowan ones as well at Kokiselei, Lepre’s team suggests. Or, another hominid species might have crafted Oldowan artifacts there.

“If Acheulian tools gave hominids an edge in Africa, then perhaps groups lacking that technology were forced to find resources elsewhere, like Eurasia,” Lepre says.

In line with that proposal, other researchers have unearthed H. erectus fossils at Dmanisi, a West Asian site as old as Kokiselei, along with simple chopping stones but no hand axes. It remains unsettled whether H. erectus, which first appeared around 2 million years ago, evolved in Africa or Asia.

Lepre’s team estimated the age of the Kokiselei tools by taking measurements in and around artifact-bearing soil of ancient reversals in Earth’s magnetic field, combined with previously dated volcanic ash layers sandwiching the finds.

Archaeologists familiar with the new paper say that it moves the origin of Acheulian tools back a bit closer to the evolutionary debut of H. erectus, an interesting but not unexpected development.

Excavations at Israel’s 'Ubeidiya Formation have recovered 1.5 million-year-old hand axes and picks, presumably made by H. erectus, that resemble those from Kokiselei, remarks Naama Goren-Inbar of the Hebrew University of Jerusalem. Acheulian sites in Tanzania and India also date to as early as 1.5 million years ago.

Some sets of Oldowan and Acheulian artifacts look much alike, implying that the same hominid species could have produced both tool types, Goren-Inbar says.

Harvard University’s Ofer Bar-Yosef agrees. “Homo erectus could have made all of the stone tools at Kokiselei,” he asserts.

Fossils are needed to confirm that H. erectus made these implements, comments John Shea of Stony Brook University in New York. Simple flakes struck off stones augmented more complex tools throughout the Stone Age, although archaeologists often ignore Oldowan artifacts at modern human sites, Shea argues.

Found in: Anthropology, Archaeology and Humans

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The world's oldest profession: chef

CHEW, CHEW, SLEEP, CHEWThis chimp and other non-human primates spend nearly half their time eating, but new research demonstrates that the cooking skills of Homo erectus allowed the lineage to save time and extract more nutrients, paving the way for bigger brains.Ronan Donovan

Nearly 2 million years ago, it seems the original naked chef was cooking up a storm. Homo erectus, the extinct hominid that’s a mere branch or so away from humans on the family tree, was the first to master cooking, new evidence suggests. This seminal event had huge implications for hominid evolution, giving the ancestors of modern humans time and energy for activities such as running, thinking deep thoughts and inventing things like the wheel and beer-can chicken.

“In the big picture, eating cooked food has huge ramifications,” says Harvard’s Chris Organ, a coauthor of the new study. Cooking and other food-processing techniques aren’t just time-savers; they provide a bigger nutritional punch than a raw diet. The new work is further evidence that cooking literally provided food for thought, making it easier for the body to extract calories from the diet that could then be used to grow a nice, big brain.

Humans are the only animals who cook, and compared to our living primate relatives we spend very little time gathering and eating food. We also have smaller jaws and teeth.

Homo erectus also had small teeth relative to others in the human lineage, and the going idea was that hominids must have figured out how to soften up their food by the time that H. erectus evolved. But behavioral traits such as the ability to whip up a puree or barbecue ribs don’t fossilize, so a real rigorous test of the H. erectus-as-chef hypothesis was lacking.

Organ and his colleagues, including Harvard’s Richard Wrangham, an early champion of the cooking hypothesis, decided to quantify the time one would expect humans to spend eating by looking at body size and feeding time in our living primate relatives. After building a family tree of primates, the researchers found that people spend a tenth as much time eating relative to their body size compared with their evolutionary cousins — a mere 4.7 percent of daily activity rather than the expected 48 percent if humans fed like other primates.

Then the team looked at tooth size within the genus Homo. From H. erectus on down to H. sapiens, teeth are much smaller than would be predicted based on what is seen in other primates, the team reports online the week of August 22 in the Proceedings of the National Academy of Sciences.

“Tooth size becomes dramatically smaller than what we would expect,” says paleoanthropologist David Strait of the University at Albany in New York, who was not involved with the work. “This is really compelling indirect evidence the human lineage became adapted to and dependent on cooking their food by the time Homo erectus evolved.”

Found in: Humans

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