In the human skull, asagittal keel, or sagittal torus, is a thickening of part or all of the midline of thefrontal bone, orparietal bones where they meet along thesagittal suture, or on both bones. Sagittal keels differ fromsagittal crests, which are found in some earlierhominins (notably the genusParanthropus) and in a range of other mammals. While a proper crest functions in anchoring themuscles of mastication to the cranium, the keel is lower and rounded in cross-section, and the jaw muscles do not attach to it.
Sagittal keels occur in several early human species, most noticeably inHomo erectus, occasionally inHomo heidelbergensis and in someUpper PaleolithicHomo sapiens specimens. Most modernHomo sapiens groups have lost them, likely as part of the general trend toward thinning of the cranial bones to make room for larger brains during thePleistocene.[1] However, there is a small portion of modern humans who have the feature, but its function andetiology are unknown. ActorPatrick Stewart and the martial artistShi Yan Ming present good examples of modern humans (Homo sapiens sapiens) with this feature. The keel appears to be tied to general cranial robustness and is more common in adult men than women and absent in children.
{{cite book}}: CS1 maint: multiple names: authors list (link)