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Fossil Friday: Another Prediction Vindicated

Photo: Hominin tibia KNM-ER 741, after Fig. 1 in Pobiner et al. 2023, fair use.

In a recent article for Fossil Friday (Bechly 2023a) I discussed the controversial hominin taxon Homo habilis and said that “this ape-like creature was rather the animal prey of contemporary human hunters than a human ancestor and producer of stone tools.” The virtual ink for this article had hardly dried when a story about a new discovery hit the news around the globe, reporting the earliest evidence of cannibalism by human ancestors about 1.45 million years ago (Bower 2023Metcalfe 2023Tozer 2023Zhao 2023).

In 1970 the famous paleoanthropologist Mary Leakey discovered a fragment of a hominin tibia at the Koobi Fora locality in the Turkana region of Kenya. It was first considered as belonging to Australopithecus (Leakey 1971, Leakey & Leakey 1977), but later attributed to Homo erectus (Walker & Leakey 1993). However, Wood (2011) remarked about this fossil in the prestigious Wiley-Blackwell Encyclopedia of Human Evolution that its “current conventional taxonomic allocation is H. erectus or Hominin gen et sp. indet.” and “because so little is known about the tibial morphology of early hominins other than Australopithecus afarensis it may be premature to rule out the possibility that it belongs to Homo habilis or Paranthropus boisei.” Consequently, Pobiner et al. (2023) cautioned that “due to the taxonomic uncertainty of this fossil, we simply refer to it in this study as a hominin (hominin gen. et sp. indet).”

Cut Marks by Stone Tools

More than a half century after the initial discovery of the fossil bone, Pobiner et al. (2023) had reanalyzed the material and found on this leg bone several cut marks that were probably made by stone tools. Control experiments indeed confirmed that similar marks result from butchering activity with stone tools, which the authors interpreted as evidence for cannibalism among early humans.

Even though this fossil is slightly younger than the youngest known finds of Homo habilis, it is still contemporary with other ape-like hominins of the genera Australopithecus and Paranthropus. Considering its taxonomic uncertainty, the bone more likely belonged to an australopithecine-like Homo habilis than to a contemporary member of genuine Homo erectus (= Homo ergaster), who could rather have been the hunter. In the latter case this could hardly be called cannibalism and instead would simply be an instance of human hunting and butchering of large hominid primates that is still common in the notorious bushmeat trade of West Africa today. An article in the New York Times agreed that the cannibalism claim might rather be mere clickbait and that “the field has a long history of overstating such claims” (Lidz 2023). You don’t say.

Anyway, this case arguably represents yet another empirical prediction by Darwin critics, which is vindicated by modern science, confirming a consistent pattern that I recently emphasized in another article for Fossil Friday (Bechly 2023b).