Eating meat: How did it help our ancestors?

Human beings and our ancestors have long been meat eaters. Though the packaging might have changed a bit from braaied mammoth to processed polony and other delicacies, meat has long been a key part of our diet. What importance has eating meat held in the story of human evolution?

If you could go back in time, about 2.5-million years, to Swartkrans and surrounds in the Cradle of Humankind, you would find two groups of hominids living there. Both groups are quite clearly non-human, but they do walk upright like we do. After watching the two groups in their habitats for a few days, you observe some differences in their diet.

One group seems to prefer vegetables. Its members do eat meat, but very little. Everything they eat is raw. And, they have very different jaws to us – big, powerful jaws that can crush seeds, hard nuts and other vegetation.

The other group has a slightly different diet. These hominids eat a balance of meat and vegetable matter. They are able to use fire to cook their food. They have much smaller jaws and teeth, similar to ours.

One of these groups is destined to evolve into modern humans, and the other will eventually die out. No prizes for guessing which is which; the hominids in the group that eats more meat are our direct ancestors. Their species is called Homo ergaster. They share the same the genus – Homo – as our own species, Homo sapiens, and that’s a good way of remembering that they’re related to us.

The hominids in the other group, belonging to the genus and species Paranthropus robustus, are not directly related to us and evidently did not have the same success as Homo ergaster. Fossil records indicate that their evolutionary line came to an end just over 1-million years ago. They were a branch of the hominid family tree that broke off and died out. What made the difference for our ancestors?

Professor Francis Thackeray, director of the Institute for Human Evolution, explains how eating meat was essential for the early Homo species, such as Homo ergaster: “The consumption of meat is related to the intake of protein, and the synthesis of the muscles and brain,” he says. “This would certainly have given them an advantage.”

Fuelled by the proteins and nutrients extracted from meat, the size of the brain in early Homo increased “dramatically fast”, says Thackeray. “Brain size, relative to body size, increased exponentially over the next 2-million years.”

According to Thackeray, there is evidence suggesting that these early ancestors were scavengers, such as bone marrow residue found on ancient stone artefacts. The use of controlled fire also played an important role in giving Homo ergaster an advantage. “Fire could get rid of bacteria in the meat; bacteria that could potentially kill,” he says.

The earliest fossil evidence of controlled fire in southern Africa has been discovered at Swartkrans and dates back to about 1-million years ago. So Swartkrans was perhaps the place of South Africa’s first ever braai. (Slightly older evidence of controlled use of fire has been found in East Africa.)

Cooked meat is also easier to chew, and this goes some way to explaining the smaller teeth of the Homo genus, compared to the large chewing muscles and teeth of Paranthropus robustus, described above. In addition, says Thackeray, fires could be used to ward off predatory carnivores – again increasing the chances of survival.

We can see that eating meat was vital to the story of human evolution. But nowadays we are in a position to evaluate the need for meat in our diets; we no longer need to follow the desire for it instinctively. With a carefully planned diet, it has become possible to avoid meat largely or completely and still be healthy.

Apart from the ethical considerations regarding eating meat, there may be an evolutionary need to change our habits. The United Nations issued a warning as far back as 2006 linking animal farming to high greenhouse gas emissions and other environmental damage. Eating meat in the quantities we do has serious implications for global warming.

Our ancestors ate meat while slowly learning to dominate their environment, but modern humans may need to change their diet in order to save their environment!

Professor Francis Thackeray, along with Eddie Odes, will give a presentation at Maropeng later this year about a new system of hominid fossil classification. The proposed system will disregard classifications by genus and species, and will look at mathematical models that can classify fossils by degrees of similarity between one another.