While vegetarian diets are likely to be healthier for people today, new studies suggest that eating meat may have helped the brains of pre-human ancestors to grow over a few million years, reports LiveScience.
One study, published last month in the journal Proceedings of the National Academy of Sciences, concluded that humans have exceptionally large, neuron-rich brains for their body size.
In contrast, gorillas, which are three times bigger than humans, have smaller brains and three times fewer neurons. Scientists believe this difference is because of the gorillas' vegan diet, which requires hours of eating only plants.
Researchers from the Federal University of Rio de Janeiro in Brazil calculated that gorillas would need an additional 733 calories a day to evolve a humanlike brain.
Humans eating only raw vegetation would have required nine hours a day to consume enough calories. A vegan diet would have been unlikely given the danger and other problems of gathering so much food.
Lead researcher Suzana Herculano-Houzel told LiveScience: "The bottom line is, it is certainly possible to survive on an exclusively raw diet in our modern day, but it was most likely impossible to survive on an exclusively raw diet when our species appeared."
The second study, published in October the journal PLoS ONE, examined the remains of a pre-human toddler who died from malnutrition about 1.5 million years ago in Tanzania.
Studies revealed that the child had porotic hyperostosis, a type of spongy bone growth associated with low levels of dietary iron and vitamins B9 and B12.
Researchers believe that the child's mother's breast milk lacked key nutrients, or the child did not eat enough nutrients directly from meat or eggs.
The study's lead author, Manuel Domínguez-Rodrigo, an archaeologist at Complutense University in Madrid, told LiveScience: "Carnivore animals, whether terrestrial or aquatic, are bigger brained than herbivores. There is no [traditional] society that live as vegans."
However, these days, given the amount of saturated fats in factory-produced animal products, a plant-based diet is probably healthier.