That idea remains controversial in the field, however. Or, as Luncz put it: “An accidental stone breakage could have led us down the evolutionary trajectory of making stone tools.” Then, far later - perhaps alongside some kill where they had used rocks to hammer open bones to get at the marrow within - early humans may have turned to these razor-sharp flakes, which would once have been discarded as trash, to begin cutting up meat. In one possible scenario, ancient humans - like modern macaques - could have first produced stone flakes as a byproduct as they bashed apart bones, nuts or shellfish with rocks. It presupposes axe-swinging early humans with brains big enough to plan their “extraction” of the perfect flakes from rocks and hand-object movement sophisticated enough to deliver it.īy contrast, the Planck team’s findings suggest another possibility - that the evolution of human tool use could have been more fitful and staggered. That narrative requires a lot of additional steps, Luncz said. In many ways, the Science paper lays the groundwork for a more intuitive story of human evolution than the idea that stone flakes - and the human cultural flowering they enabled - sprung forth by deliberate invention. That points to a possibility that could throw a wrench into the established narrative, Luncz said: that “all the conoidal flakes we find in the archaeological record - deemed to be intentionally made - could be unintentional byproducts.” That collision sometimes strikes a flake off of one of the rocks - something very similar to the toolmaking process archeologists call “knapping.”Īncient humans used knapping to break apart rocks to create an incredibly flexible set of tools - the earliest forms of which cannot be distinguished from the ones macaques made by accident. There they break open the palm fruit’s oil-rich pit between hand-wielded hammer rocks and a thick, flat stone that functions as an anvil.Ĭamera traps showed that when the nut-cracking monkeys miss a strike, the two stones bang together. In an abandoned oil palm plantation on a national park site, the monkeys would create nut-cracking ‘stations’ beneath the feral trees. In particular, the monkeys targeted the hard, oil-rich nuts of African oil palms - introduced as a cash crop across the region. The Planck group found the first evidence of macaques adapting this seafood-foraging use of stone tools to another food: nuts. Such narrow stones are perfect for breaking open the brittle shells, while wider rocks risk smashing them into sharp fragments - endangering the incautious monkey who tries to stick its face into the jagged hole. Macaques foraging on beaches choose out long, narrow and heavy stones - what anthropologists call an ‘axe hammer’ - to pop open oyster shells. This use can be surprisingly sophisticated. Long-tailed macaques - the small, mischievous and social primates often seen in Southeast Asian cities and temple complexes - use stones to break through shells and get at the meat inside. Tool use in nonhuman primates is nothing new.
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