Question

Orthognathous face occurs in
A. Cro-Magnon man
B. Modern man
C. Ramopithecus
D. None of the above

Answer 1

Hint: Ramopithecus have prognathous faces that extend forward of the anterior cranial fossa and not all modern man has a face with straight jaw.

Complete Answer:
(I) Orthognathous face is a face with a straight jaw that means having the front of the head or the skull nearly perpendicular. In this form of face, the lower jaw is not projected outward, but both jaws are straight. The facial angle of the orthognathous skull is large.
(II) Prognathous face is a face with a lower jaw that projects forward especially to an angle. In this form of face, the lower jaw is projected outward. The facial angle of a prognathous skull is large.
A) Cro-Magnon man had an orthognathous face with an arrow, a raised nose, a broad and arched forehead, moderate brow ridges, powerful jaws with a man-like dentition, and a well-developed chin.
Their front of the head and the skull is nearly perpendicular.
B) Normally, modern humans have orthognathous faces, but in case of some people we can also see the prognathous faces. The prognathous faces have extended forward of the anterior cranial fossa. The face angle of the prognathous skull is small.
C) Ramopithecus is a genus of apes which is extinct. Apes have prognathous faces that extend forward of the anterior cranial fossa.

Thus, the correct answer is option A, i.e., Cro-Magnon man.

Note: The evolution of an orthognathous face in humans is likely related to a decrease in the size of chewing muscles and teeth, and may be to changes in masticatory lever arm or load arm relationships reflecting a decreased need for production of powerful bite forces in the anterior dentition.