Professor Lee Berger holds the Sidiba skull from which alot of diet information has been garnered by examining the plaque deposited on the teeth. 270612. Picture: Chris Collingridge 988

Johannesburg - Maybe if they had practised better dental hygiene we would never have known.

But they didn’t – and for the first time, scientists have been given a peek of what was on the menu two million years ago.

This thanks to the stuff dentists scrap off teeth everyday – plaque.

Palaeoanthropologists now have direct evidence of what a hominid ate. And it surprised them.

By using three different scientific techniques, scientists believe that two individuals of the species Australopithecus sediba ate bark, palms, fruit, shrubs and herbs.

“I must say no one expected bark on the menu,” said the leader of the project Professor Lee Berger, of the Institute of Human Evolution at Wits University. “Bark, however is commonly munched on by modern primates,” he said.

Before the study, scientists had suspected that sediba would have had a diet similar to other hominid species of the time – that they would have eaten food collected from a savanna environment.

“What we know now is that sediba was feeding in a closed, forested environment,” said Dr Amanda Henry, a palaeobotanist at the Max Planck Institute, in Leipzig Germany.

Henry studied the calculus or dental plague found on the teeth of the two fossils. The wear on the teeth and diet is more like that of a giraffe, than a fellow hominin, said Berger.

The team also looked for signs of meat eating, but found no evidence of this.

The two sediba specimens, an elderly female, and a young male were considered ideal for this study, because of the preservation of their remains. It is believed that they died shortly after falling into a sinkhole. The pair was discovered in 2008, at Malapa, a site about 40 kilometres west of Joburg.

To date they are the most well- preserved hominin skeletons found, and there is debate that this species is a direct ancestor of man.

The latest find is to appear in the latest addition of Nature.

What allowed this look at sediba’s eating habits was the use of isotope analysis, dental micro wear analysis and the examination of the dental calculus and tartar discovered on the fossils’ teeth.

Henry examined the calculus by scrapping off some of the tartar with a dentist’s pick. Calculus, Henry explained, starts out as normal plaque that builds up.

Under a microscope, she was able to identify phytoliths, silica structures that are found in plants.

At Wits university, Associate Professor Marion Bamford, was able to identify the origins of the phytoliths from their shapes and sizes. “What they were eating then, we would have found it a difficult diet to digest,” explained Henry.

The idea for the study came after Berger noticed staining on the teeth and decided to investigate using the three techniques (see box).

“Before I could tell you it lived here, so we suspect it ate this. Now we can say this is what it ate,” Berger explained.

Now the team are examining other hominid fossils, hoping their dental hygiene was just as bad and plaque can be collected from their teeth.

Dental calculus

The study of dental calculus is a discipline that is still new.

It emerged in the mid 2000s and over the last half-a-decade, scientists like Dr Amanda Henry have examined the teeth of not only ancient humans, but some of our relatives like Neanderthals.

Dental calculus is the deposit of minerals, food particles and bacteria. It hardens through the action of saliva and can only be removed with a dentist’s pick. By finding phytoliths, silica structures that can survive millions of years, plant material can be identified. Academics like Associate Professor Marion Bamford at Wits university have built up archives of modern phytoliths that she compares to those found in the calculus.

Carbon Isotope Analysis

This involves studying carbon isotope pathways through the food chain

Grasses follow a C4 pathway, while trees, shrubs and herbs follow a C3 pathway. The animals that eat these plants will also show a C4 or C3 preference. Even examining the teeth of carnivores will reveal if they preyed on animals that feed on C4 grasses or C3 plants. Sediba showed a preference for eating C3 plants.

The problem with this analysis is that it can’t narrow food types down to species.

Micro wear analysis

This is the examination of microscopic scratches and pits on the tooth. Through high resolution and the creation of caste of the tooth scientists can tell if the animal was eating hard or soft foods. Micro wear analysis give an indication of what the creature was eating within a period of two weeks of its death. Hard foods, in the case of sediba, probably included nuts, roots and seeds. - The Star