Nutrition in Hominidae

Teeth fossilise beautifully. Soft tissue does not. So if you want to know what an extinct human relative ate, the skull and the teeth are almost all you have — which makes them extremely useful and slightly dangerous at the same time. This page covers how the deduction works, and where it goes wrong.

The family, and the diets in it

Hominidae is the great ape family: humans, chimpanzees, gorillas and orangutans. Gibbons are close relatives, but they sit in a separate family, Hylobatidae. Both families belong to the wider ape group, so you will sometimes see gibbons listed loosely alongside the hominids.

Most living hominids are omnivores, meaning their nutrition comes from a combination of animal and plant material. Within that, the emphasis differs:

• Chimps are mainly frugivores — their main diet is fruit, though they also eat other plant matter and some small mammals.
• Gorillas are mainly herbivores, feeding mostly on leafy vegetation, though they do sometimes eat insects.

The jaw follows the food

Studying the skulls of living hominids shows that the jaw and dentition of each species are specialised for its particular diet.

• Chimps have relatively small jaw muscles, only strong enough to chew softer fruit and animal tissue. They have small incisors and long canines, which suit biting and tearing meat.
• Gorillas have very strong jaw muscles for biting and grinding tough vegetation, and large molars and premolars for grinding it down.

The four types of teeth

• Incisors are chisel shaped, for cutting and biting.
• Canines are pointed, for holding and tearing.
• Premolars and molars are flat and ridged, for grinding.

Reading diet from a fossil

Because there is a clear relationship between diet and dentition in living hominids, the same principle can be applied to extinct hominid species. Skulls and jaws are often well preserved, so scientists can study them and work out both what those species ate and the structure of the ecosystems they lived in.

Extinct hominids you may meet include Australopithecus africanus, Paranthropus robustus, Homo floresiensis and Homo neanderthalensis.

Paranthropus robustus — a tough plant diet

• The skull shape is robust, similar to a modern gorilla, with attachment points for large jaw muscles for chewing tough vegetation.
• Large molars and premolars for grinding.
• Thick tooth enamel, protecting the teeth from damage by tough plant matter.

Homo floresiensis — mostly plants, possibly some meat

• Large premolars and small canines.
• Square, robust jaws, a feature shared with plant-eating gorillas.
• Tooth abrasion patterns suggest a fibrous, plant-based diet.
• Their skulls are more similar in shape to humans than other human ancestors, which suggests reduced biting forces.
• Evidence of hunting and cutting tools gives separate support for some meat eating.

Where the deduction breaks down

This is the part students skip and examiners reward. Dentition can sometimes be clearly linked to diet, but teeth do not always give a perfect indication of what a species eats:

• Humans eat quite a lot of meat, but our teeth look more like those of plant-eaters.
• Orangutans and gorillas have pointed canines but do not eat meat.
• Male chimps have longer canines than females, despite eating the same diet.

The reason is that teeth play a role in other processes too — defending territory, or competing for mates. So other factors have to be considered before drawing conclusions about the diets of human ancestors.

One way to get better evidence is to study fossil teeth under a microscope and look for patterns of abrasion, which can indicate diet more directly than shape alone.

Worked examples