The study adds subtlety to the “meat made us human” notion, and they may be of interest to anyone who bases their eating on the belief that early humans were particularly meat-dependent.

The debate over whether eating meat makes us human has only gotten more convoluted.

The regular consumption of meat distinguishes humans from other primates, but a new study published Monday in the journal Proceedings of the National Academy of Sciences casts doubt on the exact role it played in early human evolution.

According to the research team, the research adds nuance to the “meat made us human” theory and may be of interest to today people who base their diet habits on the belief that early humans were especially reliant on meat. 

Early human ancestors began making stone tools and using them to butcher animals between 2 million and 3 million years ago. The butchery markings discovered on bones — the intentional slicing and scraping performed with sharp-edged implements — can be used to infer meat consumption. It is undeniable that the increased use of tools and changes in food had a significant impact on human evolution.

What is contested, however, are the specifics of this phenomenon and whether or not previous behavior truly explains whether or not humans require meat to survive.

The current study bases its findings on the hypothesis that important human characteristics, such as larger brains, first appeared in the human progenitor Homo erectus, and that these qualities are linked to a dietary shift toward more meat consumption. However, the authors of the study assert that their analysis of published data shows no increase in evidence for meat consumption following the development of Homo erectus, casting doubt on the “meat made us human” theory.

“It’s clear that eating meat has been important for many groups of humans throughout much of human history and prehistory,” says lead author W. Andrew Barr. “But the idea that there was a sudden evolutionary event where meat eating went from being relatively unimportant to being so central that it drove the evolution of key human traits just doesn’t shake out in our analysis of the published evidence.” 

He explained that most research on the origins of human meat eating has focused on “very well preserved sites at a few well-known research areas.” Barr and his colleagues looked at data from 59 of these sites in eastern Africa, which date from between 2.6 million and 1.2 million years ago and reflect human activity. Animal bones with tool cut marks were found in abundance, indicating that humans ate meat in large quantities.

“We used the number of paleontological sites and the number of species preserved at those sites as a barometer for how much fossil-preservation potential there is in a given time period, and then we used that background level of sampling to contextualize the amount of cut-mark evidence preserved in the same period,” he adds.

This research implies that the profusion of cut marks on bones is due to a sampling bias — an emphasis on excavating samples from sites associated with this progenitor and time period — rather than an increase in meat consumption alongside Homo erectus. According to the study authors, there was a continuous increase in the amount of meat-eating evidence after Homo erectus appeared, even after controlling for differences in sampling intensity.

Competing theories and criticisms of the technique, however, cast doubt on the study’s result. In an email, Fred Spoor, a professor of evolutionary anatomy at University College London who was not involved in this study, stated that the focus on brain size as a defining trait of Homo erectus is “perhaps a little misplaced.” Homo erectus, Homo habilis, and Homo rudolfensis have similar brain sizes, according to scientists. Only later Homo erectus had a significantly larger brain.

According to Spoor, Homo erectus has smaller molars than other species, which is linked to chewing capacity and food. This shift is assumed to represent a transition away from a predominantly plant-based diet and toward a more mixed diet, which includes more meat.

Tim White, co-director of the University of California, Berkeley’s Human Evolution Research Center, stated in an email that the study’s data is “inadequate” for determining if “Homo erectus behavior and anatomy depended on an increased amount of meat in the diet.”

With the facts given, White, who was not engaged in this study, said it’s tough to come to a conclusion: Because of overlaps in the fossil record, it is impossible to say which Homo species was responsible for the stone tools and bone changes, and the approach used to determine whether markings on bones were generated by humans varies throughout the research included in the overall analysis.

According to White, brain size is not solely related to meat consumption in carnivores. “The largest brained mammals achieved large relative brain sizes by highly divergent paths,” according to a study published in the journal Evolutionary Biology in 2021. Baboons, on the other hand, have larger brains when they dwell in larger groups.

The study’s robustness, as well as the debate surrounding it, exemplify the difficulties in showing broad trends in human evolution with the information available. Other possibilities, according to Barr and his colleagues, could explain why some physical and behavioral aspects associated with modern humans arose, such as the use of fire to cook, which may have boosted nutritional availability. According to the study team, these are intriguing suggestions, but they are also devoid of proof.

Modern humans will have to wrestle with the question of whether or not to continue eating meat as scientists continue to gather evidence and add depth to the “meat made us human” idea. Meat may have been important in human evolution, but processed meat is nothing like what our forefathers ate.

Image Credit: Getty

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