January 26, 2006

Expanding Heads and Shrinking Faces

From the BBC news story Time changes modern human's face:
Researchers have found that the shape of the human skull has changed significantly over the past 650 years.

Modern people possess less prominent features but higher foreheads than our medieval ancestors.

Writing in the British Dental Journal, the team took careful measurements of groups of skulls spanning across 30 generations.

The scientists said the differences between past and present skull shapes were "striking".


The two principal differences discovered were that our ancestors had more prominent features, but their cranial vault - the distance measured from the eyes to the top of the skull - was smaller.

Dr Peter Rock, lead author of the study and director of orthodontistry at Birmingham University, told the BBC News website: "The astonishing finding is the increased cranial vault heights.

"The increase is very considerable. For example, the vault height of the plague skulls were 80mm, and the modern ones were 95mm - that's in the order of 20% bigger, which is really rather a lot."

He suggests that the increase in size may be due to an increase in mental capacity over the ages.
The scientists took samples from a sunken ship, the Mary Rose, and from plague victims. The latter sample might be biased, since different head shapes have been shown in the past to have better chances of survival; however, the sample from the Mary Rose should be random, and the two historical samples tend to agree in their differentiation from modern populations.

From the paper:
For S-CVa, the measurement that is most representative of the anterior cranial fossa, there were significant differences between all three groups with size increasing through the ages. The anterior cranial fossa houses the frontal lobe of the brain, the great development of which is often held to be the major distinction between the human race and other primates. In particular the prefrontal areas are concerned with intellect35 and the increased intracranial dimensions and high foreheads of the modern group are evidence that brain size has increased over the centuries.
British Dental Journal (2006); 200, 33-37. doi: 10.1038/sj.bdj.4813122Help

A cephalometric comparison of skulls from the fourteenth, sixteenth and twentieth centuries

W. P. Rock, A. M. Sabieha and R. I. W. Evans

Objectives To evaluate changes in the size and shape of the skull and jaws in British populations between the thirteenth and twentieth centuries.

Method Lateral cephalometric radiograms were obtained from skulls of three groups of subjects: 30 skulls were from the remains of those who died in the London Black Death epidemic of 1348, 54 skulls were recovered from the wreck of the Mary Rose which sank in 1545 and 31 skulls were representative of modern cephalometric values.

Results Horizontal measurements in the base of the anterior cranial fossa and in the maxillary complex were greater in the modern group than in the medieval skulls. Cranial vault measurements were significantly higher (P = 0.000) in the twentieth century skulls, especially in the anterior cranial fossa.

Conclusion Results suggest that our medieval ancestors had more prominent faces and smaller cranial vaults than modern man.


1 comment:

Hugh-EMC said...

Ive read that modern human brains are actually shrinking. How would larger cranial vaults explain this? Are some ones measurements incorrect?