Researchers working in Kenya's archaeologically prolific Lake Turkana region claim to have uncovered a set of 3.3-million-year-old stone tools. That's 700,000 years older than the previous record, and predates evidence for the evolutionary origins of the genus Homo by half a million years.

Above: A satellite image of Lake Turkana, where the stone tools – and many other artifacts and fossils of human ancestors – have been recovered

NPR's Chris Joyce reports on the findings of Stony Brook University archaeologist Sonia Harmand and her colleagues, which were announced Tuesday at the annual meeting of the Paleoanthropology Society in San Francisco:

[The 3.3-million-year-old dating] is remarkable because it's well before the human genus, Homo, emerged 2.8 million years ago. So clearly these early humans didn't make these tools. The team presumes they were made by an early ancestor of humans, probably a member of a genus called Australopithecus. The famous ape-like creature known as Lucy was from that genus and first appeared in Africa about four million years ago.

Leading stone tool experts who've seen the tools say they have the markings of a process called "knapping." Knapping a piece of stone produces flakes that can have sharp edges and are useful for working with plants, nuts or meat. These flakes can be distinguished from naturally occurring pieces of rock. Knapping also leaves characteristic marks on the rock from which the flakes are chipped.

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In 2010, researchers working in the Dikika region of Ethiopia reported evidence of "stone-tool-inflicted marks" on animal bones dating to somewhere in the range of 3.24- to 3.42-million years ago. This team, too, attributed the use of stone tools to Australopithecus afarensis. Their evidence was indirect (stone-tool-inflicted-marks, however compelling they may be, are not stone tools), and, perhaps unsurprisingly, controversial; but this most recent discovery by Harmand and her colleagues provides what multiple outside experts have called powerful corroborating evidence of purposeful and intentional tool-making long before the evolution of modern humans.

H/t NPR. For more information, see Michael Baltar's coverage of Tuesday's announcement over at Science. See also Baltar's past coverage of interesting experimental evidence for the co-evolution of tool-making and language.