New Study of Molar Size Regulation in Hominins

Related Articles

Related Articles

The molar size relationship is one of the peculiar characteristics of the different species of hominins and various theories have been proposed to account for this, as well as the differences in shape between the different kinds of teeth (incisors, canines, premolars and molars).

The latest theory, called the inhibitory cascade model, arose out of experiments with mice embryos, and in 2016 it was applied theoretically to fossil hominins, with satisfactory results.

It appeared that all hominins satisfy the inhibitory cascade model. In a paper by the Dental Anthropology Group at the Centro Nacional de Investigación sobre la evolución Humana (CENIEH), published recently in the Journal of Anatomy, this model was tested on the molar sample from the individuals identified at the Sima de los Huesos site, situated in the Sierra de Atapuerca (Burgos).

 

The results match the model generated in mice extraordinarily well, thus confirming the theory’s utility once more. “Nevertheless, our conclusions have brought out an anomaly in the model, when it is applied to the oldest species of the genus Homo”, explains José María Bermúdez de Castro, Paleobiology Program Coordinator at the CENIEH and lead author of this work.

Increasing and decreasing patterns
In the genera Ardipithecus, Australopithecus and Paranthropus, as well as in Homo habilis, the size pattern is increasing and fits the premises of the inhibitory cascade model perfectly. The same thing happens in Homo sapiens, except that the pattern is decreasing, with the first molar larger than the second, which in turn is bigger than the third one (wisdom tooth).

Application of the inhibitory cascade model had led to the assumption that the switch from increasing to decreasing pattern would have arisen a little under two million years ago, perhaps coinciding with the transition between the genera Australopithecus and Homo. “However, in our work we noticed that this change could have required at least a million years to take place”, states Bermúdez de Castro.

The hominins from the Sima de los Huesos, which are around 430,000 years old, are a good example of that transition, whereas most specimens of Homo ergaster, Homo erectus, Homo antecessor and Homo heidelbergensis, as well as other species, do not fit the inhibitory cascade model. “Our idea is to continue our research to determine which genetic mechanisms lie behind this anomaly in the model”, says Bermúdez de Castro.

CENIEH

Header Image – Mandible AT-1 from Sima de los Huesos – Image Credit : Mario Modesto

Download the HeritageDaily mobile application on iOS and Android

More on this topic

LATEST NEWS

The Great Wall of Gorgan

The Great Wall of Gorgan, also called the "The Red Snake" or “Alexander's Barrier” is the second-longest defensive wall (after the Great Wall of China), which ran for 121 miles from a narrowing between the Caspian Sea north of Gonbade Kavous (ancient Gorgan, or Jorjan in Arabic) and the Pishkamar mountains of north-eastern Iran.

Aelia Capitolina – Roman Jerusalem

Aelia Capitolina was a Roman colony, constructed after the siege of 70 AD during the First Jewish-Roman War, when the city of Jerusalem and the Second Temple on Temple Mount was destroyed.

Wild Birds as Offerings to the Egyptian Gods

Millions of ibis and birds of prey mummies, sacrificed to the Egyptian gods Horus, Ra or Thoth, have been discovered in the necropolises of the Nile Valley.

Karahundj – The Ancient Speaking Stones

Karahundj, also called Carahunge and Zorats Karer is an ancient stone complex, constructed on a mountain plateau in the Syunik Province of Armenia.

Palaeontologists Establish Spinosaurus Was Real Life ‘River Monster’

A discovery of more than a thousand dinosaur teeth, by a team of researchers from the University of Portsmouth, proves beyond reasonable doubt that Spinosaurus, the giant predator made famous by the movie Jurassic Park III as well as the BBC documentary Planet Dinosaur was an enormous river-monster.

Archaeology Uncovers Infectious Disease Spread – 4000 Years Ago

New bioarchaeology research from a University of Otago PhD candidate has shown how infectious diseases may have spread 4000 years ago, while highlighting the dangers of letting such diseases run rife.

Buhen – The Sunken Egyptian Fortress

Buhen was an ancient Egyptian settlement and fortress, located on the West bank of the Nile in present-day Sudan.

The Modhera Sun Temple

The Sun Temple is an ancient Hindu temple complex located on a latitude of 23.6° (near Tropic of Cancer) on the banks of the Pushpavati river at Modhera in Gujarat, India.

Popular stories

The Secret Hellfire Club and the Hellfire Caves

The Hellfire Club was an exclusive membership-based organisation for high-society rakes, that was first founded in London in 1718, by Philip, Duke of Wharton, and several of society's elites.

Port Royal – The Sodom of the New World

Port Royal, originally named Cagway was an English harbour town and base of operations for buccaneers and privateers (pirates) until the great earthquake of 1692.

Matthew Hopkins – The Real Witch-Hunter

Matthew Hopkins was an infamous witch-hunter during the 17th century, who published “The Discovery of Witches” in 1647, and whose witch-hunting methods were applied during the notorious Salem Witch Trials in colonial Massachusetts.

Did Corn Fuel Cahokia’s Rise?

A new study suggests that corn was the staple subsistence crop that allowed the pre-Columbian city of Cahokia to rise to prominence and flourish for nearly 300 years.