542 years ago, during the Paleozoic, the first land animals appeared and consequently the need to hear. The sea animals needed to keep the balance and developed a special organ, but this aptitude was not enough to develop itself in the atmosphere, where perceiving vibrations from outside is vital.

That is how the selection process was initiated. Basically it was modified the disposition of the bones of the cranial cavity (apsis in Greek or absis in Latin). That led the appearance of different groups of animals; anapsids, diapsids and terapsids, depending on the structure of the cranial cavity.
 
Once this evolution was initiated, hearing, which maintains inside the organ of the primitive equilibrium balance, was developed. Due to the modification of the cranial cavity, the intracranial space was increased so that brain had more space to grow. Among others, we can mention the brains of human being, whales or dolphins as examples of very developed brains.

Finally we can mention that apart from this modification of the cranial cavity, there was another modification in the base of the cranium represented by the sphenoid bones which modified its position especially in different primates.

The sphenoid is an odd bone due to the symphysis joint located between the lower wings, in the medium of the cranial base which is part of the deep internal structure of the face, nostrils and the own cranium. It can be found among the horizontal portion of the frontal bones, the basic portion of the occipital, presenting a central body and 6 lateral extensions.

60 million years ago, Prosimian’s sphenoids were in horizontal position and they were flat, but 40 million years ago, in Simian, the sphenoids had some inclination, increasing the capacity of the occipital lobes of brain.

12 million year ago some inclination could be observed in fossils. In Australopithecus, 6 million years ago, the sphenoids’ inclination increased and 2 million years ago a new inclination of sphenoids coincided with the appearance of the Bipedalism.

Between 200.000 and 160.000 years ago, sphenoid got some inclination which can be found in Homo sapiens sapiens. This fact coincides with an increase of the brain capacity, especially the frontal lobes, and a better sanguineous irrigation to the brain.

This evolution of the osseous cranial cavity and the position of sphenoid are part of the evidences used by evolutionists against the creationist doctrines regarding the origin of mankind.