In order to reach the tongue, the nerve which supplies it, the hypoglossal nerve, has to pass through an opening in the base of the skull, called the anterior condylar canal. The amount of work a nerve has to do is reflected in its size; in turn the size of the hole through which it passes indicates the size of the nerve. So by measuring the size of the canal in the base of the skull, we can get a very good idea of how much articulatory work the tongue of the skull’s ‘owner’ had to do.
