Archive for February, 2016

The bite evolution: Your teeth will tell where you came from

Research led by Monash University evolutionary biologist Alistair Evans has shown teeth track evolution-image

Research led by Monash University evolutionary biologist Alistair Evans has shown teeth track evolution. Photo: Simon Schluter

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They’re good for biting, chewing and filling out a cheesy smile for the camera. But teeth have also been shown to be a surprisingly nifty way to track human evolution.

New research has shown that the evolution of teeth, long thought to be a random process, follows a pattern.

A team of international researchers led by Monash University evolutionary biologist Alistair Evans established the pattern applies to up to 90 per cent of human, mammal and hominins.

The main rule is that the biggest teeth for australopiths (the first branch of the hominin tree from which humans evolved) are their back molars, or wisdom teeth. Meanwhile the biggest teeth in humans is the front molar.

“It was always hard to see the forest for the trees because every fossil had to be looked at independently. But here we can see a general pattern and we can be sure that it’s definitely the case,” Dr Evans said.

The newly-defined developmental pattern, outlined in the journal Nature on Thursday, is known as “the inhibitory cascade”.

It sheds lights on how humans and other mammals develop teeth, a process which begins in the embryo.

Understanding how teeth form has uses in fields from academia to cosmetic and medical treatments.

“If we want to do any bioengineering, say grow-your-own teeth, we need to understand these processes,” Dr Evans said. “It’s fundamental research.”

The findings will also enable palaeontologists working with incomplete fossilised jaws to literally “fill in the gaps” and make an informed assessment of the size of the missing teeth.

Dr Evans said when looking at three teeth in a row, the middle tooth would be the average size of the teeth sitting either side.

“This gives us a starting point, as we can compare any new fossil with our expectations … and if we do find some exceptions or changes then we can say ‘well, something really interesting must be happening here’,” he said.

But more importantly, the realisation gives a sense of order to a process previously believed to be random.

“When people had looked at human evolution before they thought ‘everything’s changing all over the place and it’s all very confusing’,” Dr Evans said. “But what we have now is a general framework or a default pattern of development to say that pretty much all hominins and probably all mammals develop in this same way.”

The size and proportion of teeth can reveal not only when meat started to be eaten but also when cooking and the use of tools began. Each of these changes affect tooth size, because suddenly teeth could be smaller.

The 11-member research team began looking at mouse tooth development and established the “inhibitory cascade” rule before confirming the pattern in humans.

To do that they studied tooth measurements from every hominin fossil found to establish that the pattern existed there, which it did. The researchers then tested their theory out on great ape and human data to see if the pattern was evident.

“It was very obvious, immediately,” Dr Evans said. “But nobody had noticed it before.”


Henry Sapiecha