New research led by Prof Joseph Ferraro from Baylor University in Waco, Texas, has provided the oldest known evidence of hunting, scavenging and meat eating by human ancestors.

Around 2 million years ago, early human ancestors known as Oldowan hominin started to exhibit a number of adaptations that required greater daily energy expenditures, including an increase in brain and body size, heavier investment in their offspring and significant home-range expansion. Demonstrating how these early humans acquired the extra energy they needed to sustain these shifts has been the subject of much debate among scientists.

The new study, described in the open access journal PLoS ONE, offers insights in this debate with a wealth of archaeological evidence from the two million-year-old site of Kanjera South, located on the shores of Lake Victoria in Kenya.

“This study provides important early archaeological evidence for meat eating, hunting and scavenging behaviors – cornerstone adaptations that likely facilitated brain expansion in human evolution, movement of hominins out of Africa and into Eurasia, as well as important shifts in our social behavior, anatomy and physiology,” Prof Ferraro explained.

Oldowan hominins met their new energy requirements through an increased reliance on meat eating. The archaeological record at the Kanjera South site shows that they acquired an abundance of nutritious animal remains through a combination of both hunting and scavenging behaviors.

The fossil evidence for Oldowan hominin hunting is particularly compelling. The record shows that hominins acquired and butchered numerous small antelope carcasses. These animals are well represented at the site by most or all of their bones from the tops of their head to the tips of their hooves, indicating to researchers that they were transported to the site as whole carcasses.

Many of the bones also show evidence of cut marks made when Oldowan hominins used simple stone tools to remove animal flesh. Some bones also bear evidence that hominins used fist-sized stones to break them open to acquire bone marrow.

The Kanjera South site also contains a large number of isolated heads of wildebeest-sized antelopes. In contrast to small antelope carcasses, the heads of these somewhat larger individuals are able to be consumed several days after death and could be scavenged, as even the largest African predators like lions and hyenas were unable to break them open to access their nutrient-rich brains.

“Tool-wielding hominins at Kanjera South, on the other hand, could access this tissue and likely did so by scavenging these heads after the initial non-human hunters had consumed the rest of the carcass,” Prof Ferraro explained.

“Kanjera South hominins not only scavenged these head remains, they also transported them some distance to the archaeological site before breaking them open and consuming the brains. This is important because it provides the earliest archaeological evidence of this type of resource transport behavior in the human lineage.”

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Bibliographic information: Ferraro JV et al. 2013. Earliest Archaeological Evidence of Persistent Hominin Carnivory. PLoS ONE 8 (4): e62174; doi: 10.1371/journal.pone.0062174