Vegetarian Cavemen Died Out, Meat Eaters Thrived
Science is fairly certain that there were “vegetarian cavemen,” but they didn't last. There was a pre-human species of man, who lived around 2.7 million to 1 million years ago, that many scientists think existed on a vegetarian diet. New research shows that the vegetarian branch of ancient humans died off long ago, while their meat-eating cousins lived on and thrived. The dietary specialization of this vegan leaning branch of early hominin is thought to have contributed to its demise because it was unable to adapt to the changing environmental conditions that took place approximately 1 million years ago. Perhaps there is a message in this for today's vegetarians—eat meat or you too will become extinct.
Anthropologists believe that Australopithecus is the common ancestor of two branches of hominin: early Homo and Paranthropus. These two branches are marked by significant differences in morphology, the physical characteristics. In terms of diet, it is thought that early Homo was a generalist but that Paranthropus was a specialist, subsisting on on plant-based foodstuffs. Perhaps to the annoyance of today's vegetarians, Paranthropus robustus represents a branch of human evolution that did not prove successful. A group of scientists led by Vincent Balter, of École Normale Supérieure de Lyon, decided to look into the question of our distant cousins' diets. In a letter appearing in Nature, “Evidence for dietary change but not landscape use in South African early hominins,” they describe their work:
The dietary specialization of Paranthropus is thought to have contributed to its demise because it was unable to adapt to the changing environmental conditions that took place approximately 1 million years ago. From an ecological point of view, a small dietary breadth is generally correlated with narrow habitat preferences. The evaluation of the size of the home range area, in addition to the estimation of the dietary breadth, would provide a detailed picture of resource use by the hominins. Using tooth enamel, the present work investigates the dietary breadth and the home range area of South African hominins with strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) ratios, and strontium isotope (87Sr/86Sr) compositions. Dietary Sr/Ca and Ba/Ca proxies are based on the biological discrimination of Sr and Ba relative to Ca (that is, Ca biopurification), resulting in predictably lower Sr/Ca and Ba/Ca in a consumer, relative to its diet. In bones, Sr/Ca and Ba/Ca decrease concomitantly up trophic chains, but in enamel, and for a reason that is not yet fully understood, only low Ba/Ca ratios are characteristic in carnivores. Low Sr/Ca ratios are representative of browsers and carnivores, whereas high Sr/Ca or Ba/Ca ratios in enamel are characteristic in grazers. In contrast, the 87Sr/86Sr of a consumer is free of any trophic process. It only reflects the 87Sr/86Sr composition of the bedrock (substrate) on which the consumer fed because the abundance of radiogenic 87Sr is determined by normalization of the stable isotope variations relative to a reference 86Sr/88Sr ratio of 0.1194.
The basic approach is to identify our dead ancestors' diets based on elements found in their teeth. Balter et al. used lasers to analyze the enamel from fossilized teeth belonging to Australopithecus africanus, Paranthropus robustus and various early Homo. All subjects were from southern Africa. By assessing ratios of calcium, barium and strontium as well as the number of strontium isotopes, the team was able to deduce both diet and the area these individuals ranged over (caveman is really not a proper term here, but it makes a catchier headline).
What did members of P. Robustus look like and how did they differ from modern humans? P. Robustus was originally discovered in Southern Africa in 1938 by the eminent Dr. Robert Broom. From fossil evidence it was discovered that they had huge, broad cheek teeth with thick enamel and focused their chewing in the back of the jaw. Broom named them “robustus” because of these teeth. But gigantic molars were not the only adaptation to a herbivorous diet.
Paranthropus robustus, an extinct vegetarian hominin.
Large zygomatic arches—the bony arch at the outer border of the eye socket—allowed the passage of large chewing muscles to the jaw and gave them wide, dish-shaped faces. A prominent bony ridge on top of the skull provided a large area to anchor these chewing muscles to the skull. These adaptations gave P. Robustus the ability to grind down tough, fibrous foods; just the thing for a race of vegetarians.
To find out what effect diet had on the isotopes found in tooth enamel, the researchers compared the three ancient hominin genera with tooth enamel from grazers and browsers, along with that from carnivores from a previous study. When all three measured ratios—Ba/Ca, Sr/Ca and 87Sr/86Sr—are considered the dietary indications for each of the subject genera becomes clear. One of the comparison charts is shown below:
Ba/Ca ratios of hominin and bovid enamel.
A possible interpretation is that the diets of early Homo and P. robustus were typical of carnivores and browsers, respectively, whereas the diet of A. Africanus was more complex. “The diet of P. Robustus seems to have been less variable than that of A. africanus and was mainly based on woody plant foodstuffs,” Balter et al. conclude. “Our results support the idea that the degree by which woody plants and underground storage organs were consumed by A. africanus was reduced in the Homo lineage, whereas the more specialized masticatory apparatus of the robust australopithecines enabled them to have subsisted mostly on this type of food.”
The lesson that can be learned from all of this evolutionary detective work is that our hominin ancestors tried going vegetarian millions of years ago. It was an experiment that highlights the myriad of ways nature manipulates living species, always trying to create a creature with a survival advantage over the competition. In this case the answer was clear—vegetarianism was not the way forward. Indeed, P. robustus only had the cranial capacity of a gorilla and would not be considered human by most people. They were an evolutionary dead-end.
Eat meat, evolve!
As we have reported before on this blog, other hominins, meat-eating creatures all, picked up humanity's evolutionary torch. Without the protein boost gotten from eating meat our species would have never developed the large brains that are our most important survival asset. It was a combination of an omnivorous diet and climate change that made us human. Remember that when some earnest but totally misguided vegan tries to convince you “meat is murder.” Real Homo sapiens eat meat, and the only vegetarian hominins went extinct a million years ago.
Be safe, enjoy the interglacial and stay skeptical.