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Report of ancient meat-fest by human ancestors disputed

Nov. 15, 2010
Courtesy of PNAS
and World Science staff

Some re­search­ers are chal­leng­ing a re­port pub­lished last sum­mer claim­ing that an­ces­tral hu­mans seem to have butchered an­i­mal bones 3.4 mil­lion years ago.

The dis­put­ed re­port sug­gested that hu­man an­ces­tors were us­ing stone tools and eat­ing meat nearly a mil­lion years ear­li­er than pre­vi­ously doc­u­mented. The pa­per ap­peared in the Aug. 12 is­sue of the re­search jour­nal Na­ture.

But it may have lacked suf­fi­cient ev­i­dence to back it up, ac­cord­ing to re­search­ers de­tail­ing their own new study in this week’s early on­line edi­tion of the re­search jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

The orig­i­nal find­ings were based on fos­sils un­earthed in Dikika, Ethi­o­pia, of an­i­mal bones bear­ing what were de­scribed as marks made by some­one carv­ing the meat and bang­ing the bones to get at mar­row. The feeding fest was at­trib­ut­ed to Aus­tra­lo­pithecus afar­en­sis, the early hu­man an­ces­tors made fa­mous by the “Lucy” ske­l­e­ton un­cov­ered in 1974.

But in the new work, Man­u­el Dominguez-Rodrigo of Com­plutense Uni­vers­ity in Ma­drid and col­leagues con­clud­ed that the “tool marks” were more likely scratch­es caused by an­i­mals tram­pling across the bones, which at some point were bur­ied in shal­low, sandy soil. The re­search­ers com­pared the orig­i­nal find­ings with pre­vi­ous stud­ies that have ex­am­ined nat­u­ral pro­cesses, such as tram­pling, which of­ten leave marks on fos­sil sur­faces that can be mis­tak­en for tool marks. 

If cor­rect, the claims “could pro­foundly al­ter our un­der­stand­ing of hu­man evo­lu­tion,” Dominguez-Rodrigo and col­leagues wrote, but un­for­tu­nately they are “not war­rant­ed.”

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Some researchers are challenging a report published last summer claiming that ancestral humans seem to have butchered animal bones 3.4 million years ago. The disputed report suggested that human ancestors were using stone tools and eating meat nearly a million years earlier than previously documented. The paper appeared in the Aug. 12 issue of the research journal Nature. But it may have lacked sufficient evidence to back it up, according to researchers detailing their own new study in this week’s early online edition of the research journal pnas. The original findings were based on fossils unearthed in Dikika, Ethiopia, of animal bones bearing what were described as marks made by someone carving the meat and banging the bones to get at marrow. The actions were attributed to Australopithecus afarensis, the early human ancestors made famous by the “Lucy” skeleton uncovered in 1974. But in the new work, Manuel Dominguez-Rodrigo of Complutense University in Madrid and colleagues, concluded find that the “tool marks” were more likely scratches caused by animals trampling across the bones, which at some point were buried in shallow, sandy soil. The researchers compared the original findings with previous studies that have examined natural processes, such as trampling, which often leave marks on fossil surfaces that can be mistaken for tool marks. If correct, the claims “could profoundly alter our understanding of human evolution,” Dominguez-Rodrigo and colleagues wrote, but unfortunately they are “not warranted.”