Glossary · Harmony

Sexual dimorphism

Sexual dimorphism is the set of facial features that differ on average between men and women: brow ridge, jaw width, cheek fullness and lip fullness. Perception research finds feminine features raise ratings of female faces consistently, while the effect of masculine features on male faces is mixed. The bone part is structural; body fat and grooming change how it reads.

5 min readUpdated 2026-09-07By Martin Saraka

Also called: dimorphic features, facial masculinity, facial femininity

What is sexual dimorphism?

Adult male and female faces differ on average, and the differences cluster in a few places. Men tend to have a heavier brow ridge and lower-set brows, a wider and squarer lower jaw, thinner lips and flatter cheeks. Women tend to have higher, more arched brows, fuller cheeks, fuller lips and a narrower chin. Sexual dimorphism is the umbrella term for that cluster; a face is more dimorphic when it sits further from the middle in the direction typical of its sex. Forums compress this into one number. BecomeTen has no dimorphism trait; it rates jaw width, gonial angle, brow position and cheek fullness separately, each with its own workable or structural tag.

What does the perception literature actually say?

Less than the forums claim, and the two halves differ. The 2006 review of the evolutionary psychology of facial beauty found feminine features in female faces preferred fairly consistently across studies. For male faces the picture is mixed: some studies found more masculine faces preferred, others slightly feminised ones, and the direction moved with who was rating and in what context. The 2011 review in Philosophical Transactions of the Royal Society B reached the same conclusion with more data, and noted that the most repeatable effects in the literature belong to averageness, symmetry and skin, not to how heavy the brow is.

Why do forums oversell it?

Because the most dimorphic faces in film are memorable, and because it is easy to point at a brow ridge on a photo. The forum version turns an average tendency into a scoring rule, then has people compete on the one axis that is almost entirely bone. The research puts skin, symmetry and averageness ahead of masculinity, and those are where the workable levers live. See looksmaxxing without the bro-science for how BecomeTen weights the areas.

What a photo can and cannot show

A photo can show whether a brow sits low or high, whether the lower jaw is wide relative to the cheekbones, whether the cheeks are full or flat. It cannot tell which of those is bone and which is fat, grooming or lighting. A lean man with tidy brows and a week of stubble reads more dimorphic than the same man at a higher body fat with overgrown brows, and nothing in his skull changed. BecomeTen reports each part as a band, never as a masculinity percentage.

Is sexual dimorphism workable or structural?

Split. Brow ridge, jaw width, chin shape and cheekbone position are bone and tagged structural; the plan does not promise to change them and the potential image will not redraw them. Cheek fullness, jaw outline, brow grooming, facial hair and skin are workable, and they are the parts that decide how dimorphic a face reads in a photo. That is why the jaw and chin area carries a larger non-surgical ceiling than harmony does.

What actually changes how dimorphism reads?

Body fat. A 2010 study found raters pick up weight from face shape and cheek fullness reliably. Lower body fat exposes the jaw outline and flattens the cheeks, which reads more masculine; higher body fat rounds them, which reads softer. See body fat and the jawline.
Brows. Thick, low, straight brows read masculine; thin, high, arched brows read feminine. Grooming decides more of this than bone does, and it is reversible.
Beard. Stubble or a short beard widens and squares the lower face visually. It is the largest cheap lever for men whose jaw reads soft.
Camera height. A camera below eye level enlarges the jaw and heavies the brow; one above does the opposite. Shoot at eye level.

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Questions

Does a stronger brow ridge always score higher for sexual dimorphism?

No. BecomeTen has no single dimorphism score, and the perception reviews do not support one. A heavy brow can read as masculine or as tired and closed, depending on brow grooming, eye area and sleep. The rating looks at brow position as one eye-area trait and does not reward heaviness for its own sake.

Is low sexual dimorphism the reason my score is average?

Usually not. An average score means the face is close to the population average on most traits, which is exactly what the research finds ordinary faces look like. Low dimorphism is one structural detail among many; skin, hair, body fat and capture quality move the score more, and they are workable.

Can a beard raise how dimorphic my face reads on a scan?

Yes, within the jaw and chin area. A short, even beard squares the lower face and hides a soft outline, and the model reads the outline it can see. The bone tags stay structural and unchanged. It is a presentation lever, so it can be reversed, and the report says so rather than crediting the jaw itself.