sciencetech-blog

comments

Prehistoric humans had teeth that were much stronger than their modern counterparts and were more like those of sea otters, which are capable of cracking open shellfish with their jaws.

A new study of the structure of tooth enamel has found that our early human ancestors had teeth that were surprisingly similar to those of the marine mammal.

Researchers at the Max Plank Institute for Evolutionary Anthropology in Leipzig, Germany, and George Washington University, found that teeth with this structure are capable of withstanding huge bite forces.

Sea otters' teeth are so strong they are capable of cracking open shell fish like clams, as seen above

This suggests that our prehistoric ancestors jaws were far more powerful than our own, perhaps allowing them to crack open nuts and bones to get to the marrow inside.

The news could help anthropologists build up a more accurate picture of what our ancestors may have looked like.

The new study, which is published in the Royal Society journal Biology Letters, found that sea otter tooth enamel had high numbers of curved bands of crystals - 19 per millimetre.

This was found to be comparable to the number seen in large flat teeth of the hominin known as Paranthropus boisei that lived in Africa more than million years ago.

Fossilised teeth from prehistoric Homo sapiens found in Africa are also known to have 16 of these bands per millimetre.

Modern humans, however, have just 14 bands per millimetre. This banding of crystals in tooth enamel is sometimes known as decussation.

When the researchers conducted tests on the otter's teeth, they found that they were able to withstand nearly three times as much pressure before chipping than modern human teeth.

Similar chips have been found in fossilised teeth of human ancestors.

Dr Adam van Casteren, a research fellow who led the study at the Max Planck Weizmann Center for Integrative Archaeology and Anthropology, said: 'Sea otter enamel is much tougher than that of humans.

'Some sectional images of fossil hominin teeth show greater decussation than in modern humans.

'Estimates of 16 bands per millimetre in East African early Homo sapiens and 19 bands per millimetre in P. boisei fossils are strikingly similar to sea otter data.

'The explanation may be dietary — to avoid teeth being chipped during hard object feeding involving high bite forces.'

The bands of crystals in the enamal of sea otter teeth (above) were similar to those in fossilised humans

The broad flat teeth of Paranthropus boisei, seen above in this fossilised skull, have led some anthropologists to nickname the early human 'Nutcracker Man' as they believe it lived on a diet of hard nuts and fruits

Sea otters' teeth (left) were found to have similar structures to those of early fossils of Homo sapiens (right)

Fossilised remains of early hominins like P. boisei have led anthropologists to conclude that they lived on a diet of hard nuts, seeds and fruits.

They have some of the largest and flattest molars of any hominin fossil found to date and their teeth are covered in a thick layer of enamel.

However, a study in 2011 claimed that these large teeth were perhaps used by P. boisei to eat grass much like a cow.

The latest findings, however, suggest these ancient humans had a formidable bite force and suggests that they tackled food somewhat tougher than grass.

Sea otters, for example, use their powerful teeth, which the researchers found could resist chipping at an average pressure of 2,800 Pascals per half metre.

Human teeth are able to resist chipping at an average of just 1,000 Pascals per half metre.

Dr Casteren said: 'Using toughness estimates for modern human enamel, the sizes of some ante-mortem chips in fossil hominin enamel suggest kilonewton forces.

'If the toughness of sea otter enamel were assumed for robust hominins like P. boisei, then this would predict exceptionally high critical tooth fracture loads.'

Sea otters eat hard-shelled clams, mussels and crabs, often cracking them open while floating on their backs