A great evolutionary leap forward in our lineage occurred once our hominid ancestors first began to hunt game to acquire meat, which once part of their diet greatly helped them to develop larger brains – especially cooked meat. When exactly this first occurred is controversial to answer. A team of archaeologists, however, have come across the oldest evidence of hunting, scavenging and meat eating by human ancestors.

Some two million years ago, early human ancestors known as the Oldowan hominin began to exhibit certain adaptions  that required greater daily energy expenditures, including an increase in brain and body size, heavier investment in their offspring and significant home-range expansion. How these early hominids had access to the necessary resources to acquire such expensive evolutionary traits has been the subject of debate among scientists for some time. The leading theory is that they began to consume meat, acquiring it by means of hunting or scavenging game put down by specialized hunting animals like lions. Demonstrating this proved to be challenging, however.

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Recently though, a team of researchers, led by Prof Joseph Ferraro from Baylor University in Waco, Texas, has finally found tangible evidence of this behavior. The researchers collected a slew of archaeological evidence from a two million-year-old site of Kanjera South, located on the shores of Lake Victoria in Kenya. Among the vestiges collected there, the scientists found an abundance of nutritious animal remains acquired through a combination of both hunting and scavenging behaviors.

“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.

(A) KJS 7472, a small bovid metatarsal from KS-2 bearing cut marks; (B) KJS 7379, a medium-sized bovid humerus from KS3 bearing pair of hammerstone notches, the specimen is also cut-marked (not figured); (C) KJS 5447, a mammal limb bone shaft fragment from KS-2 with percussion pit and striae, the specimen is also cut-marked (not figured); (D) KJS 2565, a small bovid femur from KS-2 with numerous cut marks. Scale is 1 cm in panels (A-D); 1 mm in the panel (D) close-up. Specimen numbers are field designations, not KNM accession numbers. (c) PLoS One

Numerous antelope carcasses exhibit cut marks made when Oldowan hominins used simple stone tools to remove animal flesh. Some bones also bear evidence that hominids used fist-sized stones to break them open to acquire bone marrow. Also at the site, a large number of isolated heads of wildebeest-sized antelopes were found. These animals are a lot larger than antelopes and could be consumed for days after being collected, suggesting they 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.”

Findings were detailed in the journal PLoS One.