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Oldest evidence of tool use, meat eating identified among human ancestors

Aug. 11, 2010
Courtesy of the California Academy of Sciences
and World Science staff

Hu­man an­ces­tors were us­ing stone tools and eat­ing meat nearly a mil­lion years ear­li­er than pre­vi­ously doc­u­mented, ac­cord­ing to a new stu­dy.

Sci­en­tists led by Zere­se­nay Alem­seged of the Cal­i­for­nia Acad­e­my of Sci­ences un­earthed two fos­sil­ized an­i­mal bones in Ethi­o­pia bear­ing what they said is clear ev­i­dence of butcher­ing. 

Bones said to bear butch­er­ing marks from more than three mil­lion years ago. (Cour­tesy Ca­lif. Aca­demy of Sci­ences) 
The roughly 3.4 mil­lion-year-old bones are the first ev­i­dence that the an­ces­tral spe­cies Aus­tra­lo­pi­th­e­cus afaren­sis, to which the famed “Lucy” fos­sil be­longed, used stone tools and ate meat, said the re­search­ers. 

“Lucy,” dis­cov­ered in 1974, was for many years known as the most com­plete ske­l­e­ton of a pre-hu­man an­ces­tor of hu­mans.

The an­i­mal bones, de­scribed in the Aug. 12 is­sue of the re­search jour­nal Na­ture, bear marks that sci­en­tists said indica­te meat-carving and bang­ing to break out the mar­row.

This “dra­matic­ally shifts the known time­frame of a game-changing be­hav­ior for our an­ces­tors,” said Alem­seged, cu­ra­tor of an­thro­po­l­ogy at the Cal­i­for­nia Acad­e­my. 

“Tool use fun­da­men­tally al­tered the way our early an­ces­tors in­ter­acted with na­ture, al­low­ing them to eat new types of food and ex­ploit new ter­ri­to­ries. It al­so led to tool mak­ing…. This find will def­i­nitely force us to re­vise our text books on hu­man ev­o­lu­tion, since it pushes the ev­i­dence for tool use and meat eat­ing in our family back by nearly a mil­lion years.” 

Un­til now, the old­est known ev­i­dence of butcher­ing with stone tools came from Bouri, Ethi­o­pia, where cut-marked bones were da­ted to about 2.5 mil­lion years ago. The old­est known stone tools, da­ted to around the same time, were found at near­by Gona, Ethi­o­pia. 

The new­found bones turned up at Dikika, Ethi­o­pia, only about 200 me­ters (yards) from where Alem­seged’s team dis­cov­ered the fos­sil “Se­lam” in 2000. Widely dubbed “Lucy’s Daugh­ter,” Se­lam is be­lieved to be a young Aus­tra­lo­pith­e­cus afaren­sis girl who lived about 3.3 mil­lion years ago and is now the most com­plete ske­l­e­ton of a hu­man an­ces­tor known.

“After a dec­ade of stu­dying Se­lam’s re­mains and search­ing for ad­di­tion­al clues about her life, we can now add a sig­nif­i­cant new de­tail,” Alem­seged said. “It is very likely that Se­lam car­ried stone flakes and helped mem­bers of her family as they butchered an­i­mal re­mains,” pro­bably sca­venged.

No oth­er spe­cies of hu­man an­ces­tors lived in this part of Af­ri­ca at the time, he added. 

“With stone tools in hand to quickly pull off flesh and break open bones, an­i­mal car­casses would have be­come a more at­trac­tive source of food,” said ar­chae­o­lo­gist Shan­non McPher­ron of the Max Planck In­sti­tute for Ev­o­lu­tion­ary An­thro­po­l­ogy in Leip­zig, Germany, a mem­ber of the Dikika Re­search Proj­ect with Alem­seged. “This type of be­hav­ior sent us down a path that la­ter would lead to two of the de­fin­ing fea­tures of our spe­cies—carn­i­vory and tool ma­n­u­fac­ture and use.”

To estima­te the bones’ age, proj­ect geolo­gist Jon­a­than Wynn re­lied on the fact that they lay sand­wiched be­tween two lay­ers of vol­can­ic de­posits that had al­ready been “se­cure­ly” da­ted, he said. Both the bones came from mam­mals. One is de­scribed as a rib frag­ment from a cow-sized mam­mal, and the oth­er as a fe­mur shaft frag­ment from a goat-sized mam­mal. 

Both bones bear cuts, scrapes and hit­ting marks, re­search­ers said. Two anal­y­ses showed that the marks were made be­fore the bones fos­sil­ized; the marks were con­sist­ent with stone tool use rath­er than bit­ing, the in­ves­ti­ga­tors added. One mark was even de­ter­mined to con­tain a ti­ny, em­bed­ded bit of rock ap­par­ently left be­hind from the hack­ing.

In­ves­ti­ga­tors said it was­n’t clear wheth­er mem­bers of Lucy’s spe­cies made or simply found their tools. Re­gard­less, “we now have a grea­ter un­der­stand­ing of the se­lec­tive forc­es that were re­spon­si­ble for shap­ing the early phases of hu­man his­to­ry,” said Alem­seged. “Once our an­ces­tors started us­ing stone tools to help them scav­enge from large car­casses, they opened them­selves up to risky com­pe­ti­tion with oth­er car­ni­vores, which would likely have re­quired them to en­gage in an un­prec­e­dent­ed lev­el of team­work.”

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Human ancestors were using stone tools and eating meat nearly a million years earlier than previously documented, according to a new study. Scientists led by Zeresenay Alemseged of the California Academy of Sciences unearthed two fossilized animal bones in Ethiopia bearing what they said is clear evidence of butchering. The roughly 3.4 million-year-old bones are the first evidence that the ancestral species Australopithecus afarensis, to which the famed “Lucy” fossil belonged, used stone tools and ate meat, said the researchers. “Lucy,” discovered in 1974, was for many years known as the most complete skeleton of a pre-human ancestor of humans. The animal bones, described in the Aug. 12 issue of the research journal Nature, bear marks that scientists said indicate meat-carving and banging to break out the marow. This “dramatically shifts the known timeframe of a game-changing behavior for our ancestors,” said Alemseged, curator of anthropology at the California Academy. “Tool use fundamentally altered the way our early ancestors interacted with nature, allowing them to eat new types of food and exploit new territories. It also led to tool making…. This find will definitely force us to revise our text books on human evolution, since it pushes the evidence for tool use and meat eating in our family back by nearly a million years.” Until now, the oldest known evidence of butchering with stone tools came from Bouri, Ethiopia, where cut-marked bones were dated to about 2.5 million years ago. The oldest known stone tools, dated to around the same time, were found at nearby Gona, Ethiopia. The newfound bones turned up at Dikika, Ethiopia, only about 200 meters (yards) from where Alemseged’s team discovered the fossil “Selam” in 2000. Widely dubbed “Lucy’s Daughter,” Selam is believed to be a young Australopithecus afarensis girl who lived about 3.3 million years ago and now represents the most complete skeleton of a human ancestor known. “After a decade of studying Selam’s remains and searching for additional clues about her life, we can now add a significant new detail,” Alemseged said. “It is very likely that Selam carried stone flakes and helped members of her family as they butchered animal remains.” No other species of human ancestors lived in this part of Africa at the time, he added. “With stone tools in hand to quickly pull off flesh and break open bones, animal carcasses would have become a more attractive source of food,” said archaeologist Shannon McPherron of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, a member of the Dikika Research Project with Alemseged. “This type of behavior sent us down a path that later would lead to two of the defining features of our species—carnivory and tool manufacture and use.” To estimate the bones’ age, project geologist Jonathan Wynn relied on the fact that they lay sandwiched between two layers of volcanic deposits that had already been “securely” dated, he said. Both the bones came from mammals. One is described as a rib fragment from a cow-sized mammal, and the other as a femur shaft fragment from a goat-sized mammal. Both bones bear cuts, scrapes and hitting marks, researchers said. Two analyses showed that the marks were made before the bones fossilized; the marks were consistent with stone tool use rather than biting, the investigators added. One mark was even determined to contain a tiny, embedded bit of rock apparently left behind from the hacking. Investigators said it wasn’t clear whether members of Lucy’s species made or simply found their tools. Regardless, “we now have a greater understanding of the selective forces that were responsible for shaping the early phases of human history,” said Alemseged. “Once our ancestors started using stone tools to help them scavenge from large carcasses, they opened themselves up to risky competition with other carnivores, which would likely have required them to engage in an unprecedented level of teamwork.”