"Long before it's in the papers"
May 21, 2015


Stone tools pre-dated “man,” study finds

May 20, 2015
Courtesy of Nature
and World Science staff

Newly dis­cov­ered stone tools pre-date the emer­gence of Ho­mo, the ev­o­lu­tion­ary group that in­cludes mod­ern hu­mans, ac­cord­ing to a pub­lished stu­dy. 

The findings suggest that an­ces­tors of hu­mans pre-dating Homo made and used stone tools, scient­ists say.

Study co-author Sonia Harmand with an object believed to be a stone tool, from the Lomekwi 3 site. (Credit: MPK-WTAP)

Ho­mo, which in Lat­in means simply “man,” is a ge­nus, or clas­sifica­t­ion, that in­cludes, along with to­day’s peo­ple, ex­tinct lin­eages such as the Ne­an­der­thals and Ho­mo erec­tus.

Sci­en­tists dat­ed the ar­ti­facts, found in Ken­ya, to 3.3 mil­lion years ago, ac­cord­ing to the re­port, pub­lished in the re­search jour­nal Na­ture this week. Who might have used them is un­known. Prom­i­nent among the pre-Ho­mo hu­man rel­a­tives are the ge­nus Aus­tra­lo­pith­ecus, which had smaller brains, larg­er faces and larg­er teeth and jaws.

The re­port said its find­ings go against con­ven­tion­al wis­dom, which has as­sumed that the ori­gins of sharp-edged stone tool pro­duc­tion among humans or their relatives “were linked to the emer­gence of the ge­nus Ho­mo in re­sponse to cli­mate change and the spread of sa­van­nah grass­lands” in Afri­ca.

The tools’ shape “does not con­form to any ob­served pat­tern re­sult­ing from ac­ci­den­tal nat­u­ral rock frac­ture,” the au­thors added.

Stone-tool cul­ture as­so­ci­at­ed with Ho­mo has been dat­ed back to around 2.6 mil­lion years ago, they said. This is based on ev­i­dence from Ethi­o­pia where ar­ti­facts have turned up near re­mains of one of the ear­li­est Ho­mo fos­sils, Ho­mo ha­bilis, whose sci­en­tif­ic name means “the handy man.” This cul­ture is known as Oldowan. 

The new­found tools, un­earthed from a site called Lomekwi 3 next to Lake Turkana in Ken­ya, pre­date the Oldowan tools by around 700,000 years, ac­cord­ing to the study au­thors, So­nia Har­mand of Stony Brook Uni­vers­ity and col­leagues. The ob­jects in­clude anvils, ham­mer stones, worked cob­bles and cores, which are for mak­ing sharp edges used for cut­ting, they added.

These ar­ti­facts are more prim­i­tive than Oldowan tools, but the au­thors sug­gest that the mak­ers of the Lomekwi tools had a strong grip and good mo­tor con­trol, pro­vid­ing po­ten­tial in­sights in­to the cog­ni­tive ca­pa­bil­i­ties of early rel­a­tives of hu­mans.

The tools’ shapes and mark­ings in­di­cate they were used vig­or­ously to pound things or make sharp flakes, the re­search­ers added. The arm and hand mo­tions re­quired were probably more like those used by chim­panzees to crack nuts rath­er than the ac­tions em­ployed by the Oldowan cul­tures when us­ing their tools, the au­thors pro­pose.

Re­search over the past half-cen­tu­ry has “grad­ually pushed” the ap­pear­ance of stone tools “deeper in­to time,” and there is a good chance this will con­tin­ue, wrote Erella Ho­vers of He­brew Uni­vers­ity in Je­ru­sa­lem, in a com­men­tary accompan­ying the re­port in Na­ture.

Sci­en­tists “have long pre­dicted, on ev­o­lu­tion­ary and ar­chae­o­log­i­cal grounds, that the first stone tools should be old­er than the pre­vi­ously old­est known in­stances,” she con­tin­ued.

“Once thought to be un­ique be­hav­iors of ho­minins (the group that in­cludes hu­mans and their close ex­tinct an­ces­tors), tool use and tool mak­ing are now well doc­u­ment­ed” even among mod­ern-day chim­panzees, orangutans, go­ril­las and cer­tain mon­keys, she added. 

The sim­plest con­clu­sion from all this might be that “tool use and tool mak­ing were prac­ticed by the last com­mon an­ces­tor of chim­panzees and ho­minins,” around 7 mil­lion to 5 mil­lion years ago, she wrote. How­ever, it would seem “the mak­ing of tools from stones is un­ique to ho­minins, with the no­ta­ble ex­cep­tion of chim­pan­zee nut-cracking ham­mer stones.”

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Newly discovered stone tools pre-date the emergence of Homo, the evolutionary group that includes modern humans, according to a published study. Homo, which in Latin means simply “man,” is a genus, or classification, that includes, along with today’s people, extinct lineages such as the Neanderthals and Homo erectus. Scientists dated the artifacts, found in Kenya, to 3.3 million years ago, according to the report, published in the research journal Nature this week. Scientists believe some relative of humans pre-dating the Homo genus used them, but who is unclear. Prominent among the pre-Homo human relatives are the genus Australopithecus, which had smaller brains, larger faces and larger teeth and jaws. The report said its findings go against conventional wisdom, which “has assumed that the origins of hominin sharp-edged stone tool production were linked to the emergence of the genus Homo in response to climate change and the spread of savannah grasslands.” The shape of the tools “does not conform to any observed pattern resulting from accidental natural rock fracture,” the authors added. Stone-tool culture associated with Homo has been dated back to around 2.6 million years ago, according to the authors. This is based on evidence from Ethiopia where artifacts have turned up near remains of one of the earliest Homo fossils, Homo habilis, whose scientific name means “the handy man.” This culture is known as Oldowan. The newfound tools, unearthed from a site called Lomekwi 3 next to Lake Turkana in Kenya, predate the Oldowan tools by around 700,000 years, according to the study authors, Sonia Harmand of Stony Brook University and colleagues. The objects include anvils, hammer stones, worked cobbles and cores, which are for making sharp edges used for cutting, they added. These artifacts are more primitive than Oldowan tools, but the authors suggest that the makers of the Lomekwi tools had a strong grip and good motor control, providing potential insights into the cognitive capabilities of early relatives of humans. The tools’ shapes and markings indicate they were used vigorously to pound things or make sharp flakes, the researchers added. The arm and hand motions required were probably more like those used by chimpanzees to crack nuts rather than the actions employed by the Oldowan cultures when using their tools, the authors propose. Research over the past half-century has earliest appearance has “gradually pushed” the appearance of stone tools “deeper into time,” and there is a good chance this will continue, wrote Erella Hovers of Hebrew University in Jerusalem, in a commentary accompanying the report in Nature. Scientists “have long predicted, on evolutionary and archaeological grounds, that the first stone tools should be older than the previously oldest known instances,” she continued. “Once thought to be unique behaviors of hominins (the group that includes humans and their close extinct ancestors), tool use and tool making are now well documented” even among modern-day chimpanzees, orangutans, gorillas and certain monkeys, she added. The simplest conclusion from all this might be that “tool use and tool making were practiced by the last common ancestor of chimpanzees and hominins,” around 7 million to 5 million years ago. A further possible conclusion would be that “the making of tools from stones is unique to hominins, with the notable exception of chimpanzee nut-cracking hammer stones.”