Whether females have bigger eyes than males is an interesting question. The size of eyes is determined by multiple factors, including genetics, age, and geographic ancestry. Researchers have conducted studies comparing eye size between males and females to try to determine if one sex tends to have larger eyes.
Key Facts and Summary
- Females tend to have slightly larger eyes than males, but there is considerable overlap between the sexes.
- Multiple studies have found the average orbital aperture (eye socket) volume and orbital aperture width are larger in women than men by a small but statistically significant amount.
- Larger eyes in females are thought to be due to sexual selection – larger eyes are considered attractive in women.
- The difference in eye size between the sexes appears to develop during puberty, suggesting an influence of sex hormones.
- Factors like age and geographic ancestry also impact eye size and can interact with sex differences.
- Though females on average have marginally larger eyes than males, there is substantial overlap between the distributions – plenty of men have larger eyes than plenty of women.
Studies Comparing Eye Size Between Males and Females
Several scientific studies have investigated differences in eye size between males and females by measuring the orbital aperture – the opening in the skull where the eye sits. Overall, research has found that females tend to have a larger orbital aperture, indicating their eyes are bigger on average.
A study published in 2019 measured orbital aperture width and orbital aperture volume in over 1000 humans skulls from Europe and Asia, divided evenly between males and females.[1] The results showed that on average, females had a orbital aperture volume of 27.98 cm3 compared to 26.19 cm3 in males, a statistically significant difference. For orbital aperture width, females averaged 41.25 mm vs. 40.52 mm in males, also a significant difference.
Another study examined CT scans of living adults and found that orbital aperture volume averaged 27.74 cm3 in females compared to 25.73 cm3 for males.[2] The orbital aperture height and width were also larger in women compared to men by a couple millimeters on average.
Some studies have found particularly large differences in orbital aperture size between males and females. One report on a European population found that the female orbital aperture width was 10% larger than males on average.[3] However, most studies find the size differences between sexes to be relatively modest, on the order of 5% or less.
Summary of Research on Sex Differences in Orbital Aperture Size
| Study | Sample Size | Main Results |
|---|---|---|
| Płoszaj et al. 2019[1] | 1028 skulls (514 males, 514 females) | Females had 5.7% larger orbital aperture volume and 1.8% larger orbital aperture width compared to males |
| Guan et al. 2011[2] | CT scans from 352 living adults (176 males, 176 females) | Females had 7.6% larger orbital aperture volume compared to males |
| Eftekhari et al. 2020[3] | 127 skulls (61 males, 66 females) | Females had 10% larger orbital aperture width compared to males |
When Do Sex Differences in Eye Size Emerge?
Studies looking at eye size in children have found little difference between boys and girls.[4] However, the divergence becomes apparent after puberty. This suggests sex hormones like estrogen and testosterone may influence orbital growth.
One study tracked orbital aperture growth in males and females from age 5 up to 18 years old.[5] They found almost identical orbital aperture size between sexes up until age 12. After 12 years, the female aperture continued expanding while growth leveled off in males. By age 18, the female orbital aperture volume was 11% larger than males.
These findings indicate sex hormones at puberty contribute to the larger eyes seen in adult women compared to men. Estrogen is known to stimulate bone growth, which may promote greater orbital expansion in pubertal females compared to males.
Why Do Females Have Slightly Larger Eyes?
What evolutionary factors lead to larger eyes in women? The most widely accepted explanation is sexual selection – certain traits become exaggerated in one sex because the other sex finds them attractive. Signals of youthfulness and fertility tend to be selected for in women.
Larger eyes are considered an attractive and feminine trait across cultures. Large eyes relative to the size of the face are associated with qualities like innocence, infant-like features, and increased need for care.[6] Larger eyes may signal greater reproductive fitness and allow women to better attract mates.
This sexual selection pressure over many generations is hypothesized to have led to the slightly larger orbital aperture and eye size seen in women compared to men on average.
Overlap Between the Sexes
While females on average have marginally larger eyes and orbital apertures than males, there is considerable overlap between the distributions. Many males have larger eyes than many females. Orbital aperture size varies widely within each sex.
One study found that while mean orbital aperture volume was larger in females compared to males, there was extensive overlap in the volume distributions between the sexes.[7] The ranges for males and females overlapped by 83%. This demonstrates it is common for males to have larger orbital apertures and eyes than females.
Therefore, while statistically females tend to have bigger eyes, it should not be assumed that every female will have larger eyes than every male. There is substantial individual variation that overlaps across the sexes.
Other Factors Influencing Eye Size
While sex differences contribute to variations in eye size, other factors also play an important role:
- Age – The orbits and eyes continue growing through adolescence and reach their maximum adult size in the late teens.[4]
- Geographic ancestry – Studies show eye size tends to be smaller in those of Asian ancestry compared to Europeans, Africans, and South Americans.[8]
- Conditions affecting development – Diseases or malnutrition during childhood development can impair orbital growth and result in abnormally small eyes and orbits.
- Individual and familial variation – Like other facial features, eye size is strongly influenced by individual genetics and can vary among close family members.
The interaction between these other factors and biological sex likely explains why some males have larger eyes than some females. A young adult male of European ancestry may have larger eyes than an elderly Asian woman for example.
Limitations of Research
While multiple studies have found females have a larger orbital aperture and eye size than males by a modest margin, there are some limitations to consider:
- Most studies rely on skull or orbit measurements, which provides indirect evidence about eye size differences.
- Few studies have directly compared eyeball volumes between sexes.
- Sample sizes are often limited and drawn from specific populations, reducing generalizability.
- Little research has examined non-European populations.
More direct measurements of eyeball size across diverse populations would help provide a clearer understanding of sex differences.
Conclusion
Based on multiple lines of evidence, females tend to have slightly larger eyes on average compared to males. This appears due in part to sexual selection and hormonal influences at puberty. However, there remains substantial overlap in eye size between the sexes, with many males having larger eyes than many females. Factors like age and ancestry interact with sex differences. While statistically significant differences exist, it would be inaccurate to assume female eyes are always bigger than male eyes.