Flesh eating and brain size – A new outlook

Jessica Thompson and her colleagues proposed a new theory on human predatory patterns and the evolution of brain size in the Current Anthropology issue of February 2019. Fossil bones of large animals were found along with those of early hominins by Thompson from Dikika region of Ethiopia. An analysis of the animal bones revealed that there were cut marks suggesting that these bones were accessed for marrow by early hominins some 3.4 million years ago (mya). According to her, these were percussion marks on the bones which suggested the use of stone tools by our ancestors. There is a clear distinction between the external flesh over the bones and that inside the bones which contains marrow. The external flesh of animals mainly contains proteins, while that inside bones has mainly fat. Cutting flesh requires flake tools while crushing bones only requires ordinary stone tools. Till now, the prevailing theory states that the use of flake tool and meat consumption were mainly responsible for expansion of the brain size which ultimately stimulated the fast human evolutionary process thereafter. This happened around 2 mya. While disagreeing to the conventional theory, Thompson and her colleagues were of the opinion that early hominins may have crushed the bones of the already hunted animals to harvest the fatty marrow and the brains instead of killing the animals themselves.

Thompson says “Right around that time there appeared to be the first stone tools and butchery marks. You have the origins of our Homo genus.”

Arguing further on the issue, Thompson comments that hominins would have faced handicaps to themselves had they been eating the flesh of hunted animals because the raw flesh poses serious problems for chewing and digesting and its contamination by microbes. Besides encountering grave dangers by other predators coming to eat the flesh. On the other hand, eating marrow and brains would be easy when the rest of the flesh has been eaten by other animals and the bones are free of flesh. During that time the danger of predatory animals is also minimal. The bones could also be taken to relatively safer places away from the carcass for eating marrow. The fatty diet of hominins around 3.4 mya might have been responsible for the faster evolution of human brain as it needs animal fats for its growth.  However, this theory has many opponents who are of the view that there is no evidence of scavenging coming earlier to hunting. Nevertheless, it excites the academia for further investigation from various disciplines to confirm or reject this theory.