Human ancestors like Australopithecus – which lived around 3.5 million years ago in southern Africa – ate very little to no meat, according to new research published in the scientific journal Science. This conclusion comes from an analysis of nitrogen isotope isotopes in the fossilized tooth enamel of seven Australopithecus individuals. The data revealed that these early hominins primarily relied on plant-based diets, with little to no evidence of meat consumption.
Not really surprising as we had recently evolved to stand on two legs and probably lacked the brain power to hunt effectively. We only started using fire sometime during the following two million years as a we transitioned into "modern" humans. Fire was likely a huge motivator to begin consuming meat once the maillard reaction was "discovered". The last ice age probably kicked out hunting skills into high gear due to sparse vegetation and the need to consume more fats and proteins.
Three million years ago we ate what we could find and plants do not run away or bite. What will the next great finding be, homeless people don't eat steak?
Terribly reductive take.
There's a myriad of different edible plant species, variably digestible and non-digestible for different species.
This article outlines how the reconstructed mouth microbiom of human ancestors as far back as 100'000 years ago was already capable of breaking down starchy foods. With the advent of fire, those would've been cooked just like meats and would've facilitated a growth in brain all the same, while being more reliable a food source.
You did not quite seem to explain how it is reductive to note the lifestyle was opportunistic based upon what was easily and safely available rather than preference, instead you just seemed to say different plants exist.
It is always fun to see how offended meat-eaters get in threads like this. The beef lobby has successfully tied their product to your sense of self-worth. Congratulations, you're very macho and manly for eating meat.
Learning to use fire also opened up a lot more nutrients from plants including legumes and tubers that are inedible or less nutritious without cooking.
Increased brain size is beneficial for many things other than hunting, including cooperating to outcompete rival clans and other hominids like neanderthals.
The carnist argument in question, when applied to argue against the efficacy of plant-based diets, is essentially an appeal to nature fallacy. Learning what happened in history is interesting, but does not tell us what is beneficial to do now. If what we care about is empirical health outcomes, we should look at health outcomes data rather than trying to replicate what our ancestors did in situations that were vastly different to the ones that we find ourselves in now. And the preponderance of evidence supports equal if not better outcomes for diets that are mostly if not completely whole foods plant-based, and shows increased risk of heart disease and cancer with increased red meat and processed meat consumption.