The information on this page allows one to infer how masculine or feminine different women are, and should be used to compare high-fashion models with glamour models.

Men develop under higher androgen levels than women.  Women develop under higher estrogen levels than men.  Both androgens and estrogens affect various skeletal structures and soft tissues in different ways.  Therefore, an examination of overall physical appearance allows one to compare the ratios of testosterone (a major androgen) to estradiol (a major estrogen) that people of the same ethnic group have developed under.

Some of the major physique differences between men and women are well-known and are not addressed here.  For example, a woman with broad shoulders and a narrow pelvis is more masculinized than the typical woman.  The discussion below mostly focuses on facial features and pelvic/torso skeletal structure.  Please note that since sex hormones are only partly responsible for trait variation, it is necessary to consider a cluster of traits known to be influenced by sex hormones to assess the masculinity-femininity of a person. 

The skull

Fig 1 shows variation in [European] skull shape resulting from sex differences, after removing the size-differences factor.  The middle skull (top row) represents the average of men and women; the skulls to its left and right represent feminization (effect of estrogens) and masculinization (effect of androgens), respectively.  Note the two-dimensional matrix in the background of the middle skull; the directionality of its deformation in the background of the other two skulls represents the effects of sex hormones.

Fig 1: Change in skull shape as a function of sex, assessed via geometric morphometrics.⁽¹⁾  The first row shows transformation grids from mean centroid size into a female and into a male.  The bottom row shows corresponding generalized least-square superimpositions.  “In males, the nasoglabellar profile [region around points 1 and 2 in the figure] becomes curved and projecting, and the subnasal profile rotates clockwise.  The nasal roof is elevated, and the nasal floor shifts downwards.  The outer table of the occipital clivus rotates counterclockwise.  The chin is lowered, and the gonial region gets strongly curved [the gonion is marked at point 22].  At the occipital bone in males [back of the skull], the squamous proportion dominates over the nuchal area, and the whole basi- and neurocranium is deformed globularly.”(3)  The numbers are defined as follows: 1, Glabella; 2, Nasion; 3, Rhinion; 4, Anterior nasal spine; 5, A-point (deepest point on the curvature of the alveolar clivus in the median sagittal plane); 6, Prosthion; 7, Infradentale; 8, B-point (deepest point at the mandibular symphysis curvature [between landmark 7 and landmark 9]); 9, Menton; 10, Gnathion; 11, Vomero-sphenoid junction; 12, Basion; 13, Ophistion; 14, Inion; 15, Ophistocranion; 16, Lambda; 17, Bregma; 18, R. alveolar point (right posterior limit of the maxillary alveolar arc at the pterygo-alveolar suture); 19, R. optic canal point (most superior, medial, and anterior points of the optic canal [superior border of the posterior face]); 20, R. inf. basal border; 21, R. preangular incisure; 22, R. gonion; 23, R. ramus flexion; 24, R. condylion; 25, R. mastoid tip (most distal point at the mastoid process); 26, R. mental foramen (anterior limit); 27, R. lingula mandibulae (antero-lateral base); 28, R. foramen ovale (postero-lateral corner); 29, Posterior nasal spine.⁽¹⁾

Fig 2 summarizes the finds obtained in Fig 1.

Fig 2: Change in skull shape as a function of masculinization and feminization.⁽¹⁾

Fig 3 sums up some elements of cranial shape variation resulting from masculinization and feminization, and includes some of the changes not addressed in Fig 1.  The technical terms in Fig 3 are explained below it.

Fig 3: Cranial shape variation related to masculinization and feminization.^(2-4)In Fig 3, changes related to the mastoid process, nuchal plane (back of the skull at the nape of the neck) and external occipital protuberance are not relevant for a visual comparison based on photographs of real people because hair would typically hide the differences.  Fig 3 also mentions shape changes in the superciliary and zygomatic arches, which are explained next.  Notice the spot marked as the glabella in Figure 3.  The superciliary arches are the arches on the forehead, right above the eyebrows, which extend sideways on both sides of the glabella.  The zygomatics are the cheekbones, shown in orange in Fig 4, which also depicts the cross-hatched bony portion known as the zygomatic arch.

Fig 4: Zygomatic bones, also known as cheekbones (orange) and the zygomatic arch (cross-hatched portion).  The cheekbones are higher in males, lower in females; and the zygomatic arches are higher and thicker in males, lower and thinner in females.^{(3, 4)} 

Fig 5 shows real-life examples of the skull of a feminine woman (left) and that of a masculine man.

Fig 5: The skulls of a feminine woman (left) and a masculine man.

Fig 6 addresses change in [European] skull shape as a function of size.  Note that increasing face size sharpens the gonial angle (at point 22), giving it a masculine appearance.

Fig 6: Change in face shape as a function of size, assessed via geometric morphometrics.⁽¹⁾  The first row shows transformation grids from mean centroid size into a small individual and into a large one.  The bottom row shows corresponding generalized least-square superimpositions.  “With increasing centroid size [face size], the subnasal clivus becomes enlarged and rotates counterclockwise; the increment of the mandibular ramus [vertical portion of lower jaw bone] height leads to a more pronounced angulation at gonion [point 22]; the antero-posterior dimensions of the splanchnocranium are reduced; the face is expanded supero-inferiorly; the face appears relatively larger than the neurocranium; and the braincase becomes more globular.”⁽¹⁾  See the legend of Fig 1 for the definitions of the numbers.

There are additional changes in facial features related to sex hormones; these changes are addressed after controlling for size: the eyebrows are thicker and placed lower on the face, i.e., closer to the eyes, in males; the face is broader in the female; the distance between the eyes is greater in the female; and the chin is longer and squared in the male (Fig 7a).

Fig 7a: Face outline variation resulting from masculinization and feminization (front view, assessed via geometric morphometrics); f = female, m = male.⁽⁵⁾

In Fig 7b, the middle column represents the male-female average (northwest Europeans); the left and right columns represent equal displacements in the male and female direction, respectively.   The differences between the left and right columns represent an approximately three-fold exaggeration of average male-female differences.

Fig 7b. Sexual dimorphism in face shape; see text for details.⁽⁶⁾

Figure 7c describes how a female face is transformed by increased feminization.   The left column shows the directionality of displacement of parts of the face; the blue part moves inward and the red part outwards; stronger color implies that the directionality of the displacement is closer to right angles to the surface.   The middle column shows the magnitude of the displacement; stronger color implies greater magnitude of change; the color coding at each point is in 33% percentiles.   The right column shows change in [local] surface area; red implies increase and blue decrease; color coding at each point is in 33% percentiles, with darker colors implying the upper percentiles.

Fig 7c. Face shape change resulting from feminization of a female face; see text for details.⁽⁶⁾

Increasing feminization causes the following important facial changes:⁽⁶⁾

(key in a standing person: anterior = toward front, posterior = toward back, superior = above, inferior = below, medial = toward midline, coronal plane = vertical plane dividing body into anterior-posterior parts)

• The upper lip and philtrum area is displaced posteriorly and superiorly, and reduced in area, especially in the middle part.
• The nose becomes narrower along its length, reduces in area and is displaced posteriorly.   The tip of the nose moves posteriorly, making the nose become relatively shorter, and the tip is also displaced superiorly, which turns up the tip of the nose.
• The cheeks expand in area and are displaced outwards.
• The chin reduces in area and is displaced superiorly and posteriorly.  The angle of the mandible is displaced toward the middle of the face, and the mandible is reduced in relative length.
• The inferior ear attachment is displaced medially whereas the superior ear attachment is displaced inferiorly, leading to an overall rotation of this area in the coronal plane.
• “The superior medial orbital margins are displaced superiorly and posteriorly whereas the superior lateral margins are displaced laterally; the lateral margins are displaced laterally.”
• The medial forehead is displaced anteriorly and expands laterally; the lateral aspects are displaced anteriorly without lateral expansion.

In Fig 8, the rank-ordering along the lines of masculinity-femininity should be obvious, and the reader should now be able to justify the rank-ordering with some precision.  Reflecting the global effects of sex hormones, the rank-ordering of the overall physique of these three women along the lines of masculinity-femininity dovetails with that of their faces.

Fig 8: An example of masculine-to-feminine face shape variation.  

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