Morphological Changes Teeth, Jaws, Brain Size and Skulls

 Changes in lifestyle lead to distinct changes in the morphology of early hominins.  These changes are significant, as they allow scientists to calculate time scales and chronological order of species.

Changes in Dentition Chimpanzee Bottom view of skull: Diastema Dental arch is U-shaped Canines are very large Other teeth are large Diastema (gap) present Australopithecine Bottom view of skull: Dental arch is still slightly U-shaped Canines are reduced Other teeth are large Diastema (gap) present Human Bottom view of skull: Dental arch is less U-shaped All teeth are smaller No diastema (gap)

Diastema  The diastema allows room for the lower canine to sit comfortably in the upper jaw.  The larger the diastema, the larger the lower canines.

Dentition Changes  The most obvious change in the morphology of teeth, is the Canines have significantly reduced in size.  This can be contributed to a change in diet from chewy, fibrous vegetable matter to an omnivorous diet. The use of fire to ‘soften’ food can also be linked to this change.

Jaw  In humans the jaw is much smaller, again this can be linked to diet.  Apes jaws are much larger in comparison and can accommodate much larger teeth.

Brain Size Bipedalism  Better food sources  High in Protein  Greater brain growth  Increased ability to think  More complex behaviour

Brain Size Chimpanzee Australopithecus africanus Homo habilis Homo erectus Homo sapiens

Humans have a well-developed brain which has lead to the success of the species. Humans are the only specie that highly manipulates and controls it’s environment. Those individuals who were more accomplished at developing social relationships were better able to pass on their genes.

Skull Changes Reduced Brow ridges – Reduced Sagittal Crest – Flattened Face - Saggital Crest Brow ridge