Archaeologists find earliest evidence of stone tool making

"These tools shed light on an unexpected and previously unknown period of hominin behavior, and can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone," says Dr. Harmand, a Research Associate Professor in the Turkana Basin Institute (TBI) at Stony Brook University. "Our finding disproves the long-standing assumption that Homo habilis was the first tool maker."

The discovery was announced in a paper, 3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya, published on May 21 in Nature. Dr. Harmand, the lead author, says that the Lomekwi 3 artifacts show that at least one group of ancient hominin started intentionally "knapping" stones -- breaking off pieces with quick, hard strikes from another stone -- to make sharp tools long before previously thought.

In the 1930s, paleoanthropologists Louis and Mary Leakey unearthed early stone artifacts at Olduvai Gorge in Tanzania and named them the Oldowan tool culture. In the 1960s they found hominin fossils (in association with those Oldowan tools) that looked more like later humans -- and assigned them to a new species, Homo habilis, handy man.

"Conventional wisdom in human evolutionary studies since has supposed that the origins of knapping stone tools was linked to the emergence of the genus Homo, and this technological development was tied to climate change and the spread of savannah grasslands," says Dr. Lewis, a Research Assistant Professor at TBI. "The premise was that our lineage alone took the cognitive leap of hitting stones together to strike off sharp flakes, and that this was the foundation of our evolutionary success."

But a series of papers published in early 2015 have solidified an emerging paradigm shift in paleoanthropology -- Australopithecus africanus and other Pleistocene hominins, traditionally considered not to have made stone tools, have a human-like trabecular bone pattern in their hand bones consistent with stone tool knapping and use.

Credit getting lost for the find. One day in the field, Drs. Harmand and Lewis and their team accidently followed the wrong dry riverbed -- the only way of navigating these remote desert badlands -- and were scanning the landscape for a way back to the main channel. Local Turkana tribesman Sammy Lokorodi helped them spot the stone tools.

"The tools are much larger than later Oldowan tools, and we can see from the scars left on them when they were being made that the techniques used were more rudimentary, requiring holding the stone in two hands or resting the stone on an anvil when hitting it with a hammerstone," Dr. Harmand says. "Some of the gestures involved are reminiscent of those used by chimpanzees when they use stones to break open nuts."

The study of the Lomekwi 3 artifacts suggest they could represent a transitional technological stage -- a missing link -- between the pounding-oriented stone tool use of a more ancestral hominin and the flaking-oriented knapping of later, Oldowan toolmakers.

"The site at Lomekwi provides an ideal window into early hominin behavior across an ancient landscape. The exposures of sedimentary strata there allow us to place these activities in a detailed environmental context, and to tightly constrain their age" notes geologist Craig Feibel of Rutgers University, a co-author on the study.

The scientists dated the hominin remains by correlating the rock strata where they were discovered with well-known radiometrically dated tuffs (volcanic ash). The tools were studied by Dr. Harmand and her colleague Hélène Roche -- world experts in lithic analysis, the study of stone artifacts from the various Stone Age periods in which they were made -- to interpret physical features and reconstruct the manufacturing techniques used at the prehistoric site, including experimental replication of the tools.

Drs. Harmand and Lewis co-directed the fieldwork and analysis of the findings as part of an international, multidisciplinary team of archaeologists, paleontologists, geologists, paleoanthropologists; there are 19 other co-authors on the paper.

The Turkana Basin Institute is a privately funded, non-profit initiative founded by Richard Leakey and Stony Brook University, with a primary research focus on human prehistory and related earth and natural science studies. TBI provides permanent scientific facilities and logistical support to conduct fieldwork and research in the challenging remote environment of sub-Saharan Africa. It's committed to safeguarding the extensive fossil deposits in the region through engagement with local communities, and works with the National Museums of Kenya in scientific institutional partnerships.

Dr. Lewis wanted to be a paleoanthropologist working in East Africa since he was 13, when he read a book about the famous Lucy skeleton of Australopithecus afarensis. Dr. Harmand has always been impassioned about the quest for our origins, and the role of tools in cognitive evolution. She wanted to work in the Cradle of Humankind, where the first chapters of the human story are preserved.

"I have no doubt that these aren't the very first tools that hominins made," says Dr. Harmand, who in addition to her position at Stony Brook is a researcher at France's Centre National de la Recherche Scientifique. "They show that the knappers already had an understanding of how stones can be intentionally broken, beyond what the first hominin who accidentally hit two stones together and produced a sharp flake would have had. I think there are older, even more primitive artifacts out there."

"The paper by Harmand et al describes a truly pathbreaking discovery, and moves the date of the earliest flaked stone artifacts back by almost 3/4 of a million years. In addition, the careful documentation of the Lomekwi flaking techniques in this and forthcoming papers shows them as more primitive than those seen within the time range of Homo. This reaffirms the argument that the repeated and competent manufacture of useful sharp edges, on which we came to depend, may have been a driving factor in the evolution of our genus, both anatomically and cognitively.

"It also confirms an assertion we made in a 2002 paper ["Older than the Oldowan," Panger et al. Evolutionary Anthropology] that the oldest Oldowan artifacts at 2.5+0.15 Ma were too sophisticated to represent the dawn of human technology. Harmand's paper raises questions about who the earliest stone tool makers were -- was Kenyanthropus platyops found nearby in the same time range actually the precursor to Homo as its discoverers suggested? Stay tuned." Alison Brooks, Professor of Anthropology, Center for the Advanced Study of Human Paleobiology, George Washington University; Research Associate, Human Origins Program, Smithsonian Institution

"The Lomekwi stone tools join cut-mark evidence from Dikika in pushing the origins of stone cutting tools back to almost 3.5 million years ago. This raises new questions about the differences between stone tools made by earlier hominins and those by recent humans. The really interesting scientific question is, 'What pushed early hominins to make stone tools at that place and at that point in time? What were they doing with the tools?'" John Shea, Professor, Department of Anthropology, Stony Brook University; Research Associate, Turkana Basin Institute.