Predicting human evolution: Teeth tell the story

February 24, 2016
Cast of the skull of Lucy, the australopith Australopithecus afarensis from Ethiopia, included in the study. Credit: David Hocking

Monash University-led research has shown that the evolution of human teeth is much simpler than previously thought, and that we can predict the sizes of teeth missing from human fossils and those of our extinct close relatives (hominins).

A new study published today in the journal Nature, led by evolutionary biologist Dr Alistair Evans from Monash University, took a fresh look at the teeth of humans and hominins. The research confirms that molars, including , do follow the sizes predicted by what is called 'the inhibitory cascade' - a rule that shows how the size of one tooth affects the size of the tooth next to it. This is important because it indicates that human evolution was a lot simpler than scientists had previously thought.

Dr Alistair Evans explains how our fascination with where we come from, and what our fossil ancestors were like, has fuelled our search for new fossils and how we can interpret them.

"Teeth can tell us a lot about the lives of our ancestors, and how they evolved over the last seven million years. What makes different from our fossil relatives? Palaeontologists have worked for decades to interpret these fossils, and looked for new ways to extract more information from teeth," Dr Evans said.

Dr Evans, a research associate at Museum Victoria, discussed how this new research has challenged the accepted view that there was a lot of variation in how teeth evolved in our closest relatives.

"Our new study shows that the pattern is a lot simpler than we first thought - human evolution was much more limited," Dr Evans said.

Dr Evans led an international team of anthropologists and developmental biologists from Finland, USA, UK and Germany, using a new extensive database on fossil hominins and modern humans collected over several decades, as well as high resolution 3D imaging to see inside the .

The team then took the research a step further by applying the findings to two main groups of hominins: the species in the genus Homo (like us and Neanderthals), and australopiths, including specimens like Lucy, the famous fossil hominin from Africa.

Dr Evans explained that while it was discovered that both groups follow the inhibitory cascade, they do so slightly differently.

Dr. Alistair Evans, Monash University, examines a range of hominin skull casts that were included in the study. Credit: David Hocking

"There seems to be a key difference between the two groups of hominins - perhaps one of the things that defines our genus, Homo," Dr Evans said.

"What's really exciting is that we can then use this inhibitory cascade rule to help us predict the size of missing fossil teeth. Sometimes we find only a few teeth in a fossil. With our new insight, we can reliably estimate how big the missing teeth were. The early hominin Ardipithecus is a good example - the second milk molar has never been found, but we can now predict how big it was."

Another author on the Nature paper was Professor Grant Townsend from the University of Adelaide's School of Dentistry. The study examined of modern humans, including those in one of the world's largest collections of dental casts housed at the Adelaide Dental Hospital.

As milk teeth (image A left) and adult teeth (image A right) develop side by side within growing faces, it is not surprising to think that one set has a powerful influence on how the other set develops (image B). Credit: Illustration E. Susanne Daly. Image Gary Schwartz.

"These collections of dental casts are critical to finding our place in the hominin evolutionary tree, and advancing knowledge in the oral health of Australians," said Professor Townsend.

The findings of the study will be very useful in interpreting new hominin fossil finds, and looking at what the real drivers of were. As well as shedding new light on our evolutionary past, this simple rule provides clues about how we may evolve into the future.

Explore further: How teeth explain the tree of life

More information: "A simple rule governs the evolution and development of hominin tooth size," Nature, nature.com/articles/doi:10.1038/nature16972

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FredJose
1 / 5 (8) Feb 25, 2016
and how they evolved over the last seven million years

There's just one tiny, weeny, little, small fly in the ointment of this so-called evolution and that is that the human genome [ and in fact that of ALL other species] shows a very rapid deterioration which cannot be eliminated by natural selection.
The extensive build up of errors which goes under the radar basically means that the human population should have been extinguished in less than 100k years. Then, to make matters worse, the so-called beneficial accumulation of mutations is waaayyyyy too slow to counteract or be of any good to the population.
Hence one can safely conclude that the millions of years touted here is simply a myth. There is no concrete, documented, real, repeated and repeatable and verified evidence that there was ANY such evolution over the specified period. On the contrary the decay in the human genome is observable, verifiable, testable and documented. Tis real, unlike the mythological years.
Captain Stumpy
5 / 5 (6) Feb 25, 2016
The extensive build up of errors which goes under the radar basically means that the human population should have been extinguished in less than 100k years
@fred-troll
only if we were inbreeding far too much... you know, like being created as a single mating pair and then spreading into the world as the xtian tome represents (so, where did the wives come from for Adams kids? MONKEY'S!)

https://www.youtu...WKp44T50

http://www.ncbi.n...2267227/

https://www.youtu...O6KYPmEw

https://www.youtu...a5gkvmlU
cgsperling
5 / 5 (8) Feb 25, 2016
FredJose: Just one small fly in your logic. Errors that are detrimental cause individuals to die or not reproduce, so they get weeded out of the genome of a population.

You are yet another creationist who couldn't find his genome with both hands.
Whydening Gyre
5 / 5 (6) Feb 25, 2016
There's just one tiny, weeny, little, small fly in the ointment of this evolution and that is that the human genome [ and that of ALL other species] shows a very rapid deterioration which cannot be eliminated by natural selection.

Please cite for this "revelation". Also, that is the nature of EVOLVING.
The extensive build up of errors which goes under the radar ....

Cite for this, as well. Whose radar?
Then, to make matters worse, the so-called beneficial accumulation of mutations is waaayyyyy too slow to counteract or be of any good to the population.

They don't "accumulate". They HAPPEN. One in a million adaptations work and voila - a surviving characteristic.
There is no concrete, documented, real, repeated and repeatable and verified evidence that there was ANY such evolution over the specified period.

Your kidding, right? It's what the article is describing, fer criyi..
(cont)
Whydening Gyre
5 / 5 (6) Feb 25, 2016
Hence one can safely conclude that the millions of years touted here is simply a myth.

You only safely conclude when you don't open your eyes.
On the contrary the decay in the human genome is observable, verifiable, testable and documented. .

Wow. You don't even realize that you just described evolutionary process...
Tis real,

Yup.
unlike the mythological years

Years that are required for successive generations to pass on successful adaptations.
Quit fearing knowledge.
viko_mx
1 / 5 (6) Feb 25, 2016
The evolution is impasible and no one evolutionsist can explain what must be the principle ot fictional evolution process that must be compatible with the physical laws nad the current scientific knowledge. They can offer only general whishful explanations lacking logic and unjustified with facts. The evolution is pure religion. It have nothing to do with science and rely only pon invfintely repeating the same unsustaned mantras.
Captain Stumpy
5 / 5 (5) Feb 26, 2016
The evolution is impasible
@v
that really depends on if it is in a passing zone or not, doesn't it? i mean, if it were only traveling at 60Kph in the right lane on A-6 towards Kaiserslaturn, then i guarantee you it would be passable! heck.... might as well be parked at 60Kph!

or were you meaning something else?
The evolution is pure religion. It have nothing to do with science
Oh! then you can refute the following validated studies that support just Macroevolution?
http://www.talkor...efs.html

when you get done, refute Lenski: http://myxo.css.m...dex.html

don't' forget, since we are using SCIENCE as the standard, you must have actual evidence that is validated since that is what i presented to you!

now EITHER:
1- research scientists are all incompetent
2- research scientists are all in a conspiracy to deceive you
3- research scientists know something you don't
potholer54

since you can't prove 1 or 2
3 MUST be true!
torbjorn_b_g_larsson
5 / 5 (3) Feb 27, 2016
Beautiful, beautiful teeth!

"another creationist who couldn't find his genome with both hands"-

It isn't easy if you have no DNA (or else) backbone...

@viko: "no one evolutionsist can explain what must be the principle ot fictional evolution process that must be compatible with the physical laws nad the current scientific knowledge".

You are kidding, right!?

Population genetics was the basis for the modern synthetic theory of evolution, which married gradualism and population biology with genetics. [ https://en.wikipe...ynthesis ]

Because unlike magic peddlers scientists can't just say so, they need to know the actual facts _and become the specialists_ in their area.

Magic peddlers, still boring the rest of humanity for their personal gratification. Tells you a lot about how morally rotten to the core their magic soup is...

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