Why are women shorter than men on average?

I guess everyone has noticed that regardless of ethnicity, whether in China or abroad, women are shorter than men on average. Although we are used to the difference in height between men and women, many people still find it strange. Why is there a difference in height between men and women? Is there any scientific basis for this? Today, let's talk about this issue from a biological perspective!

01. Two conclusions about height

1. Waist-to-hip ratio: The waist-to-hip ratio determines the center of gravity of upright walking mammals. The smaller the waist-to-hip ratio, the lower the center of gravity, which generally affects the height of women (women are generally lower than men after puberty)

2. Reproductive selection: Women tend to choose taller men, and men tend to choose shorter women. This will cause changes in the reproductive success rate.

The following references are used to help you understand

02. Waist-to-hip ratio

Waist-to-hip ratio (WHR) is the ratio of waist circumference to hip circumference. The normal WHR for men and women is less than 0.8 for women and less than 0.9 for men (DGSP: S 1- Leitlinie Vorsorgeuntersuchung im Sport. 2007)

That is to say, the waist-to-hip ratio of women is smaller than that of men, in other words, women's hips are larger than men's (relatively). This is mainly due to the fat accumulation caused by pregnancy and the growth of the pelvis (CL Ogden 2004).

I believe many people have learned this in junior high school biology. Puberty is the time when the body shape of boys and girls changes the most, mainly manifested in changes in secondary sexual characteristics.

Men: beard, prominent Adam's apple, thick bones, deep voice, etc.

Women: Symptoms include well-developed breasts, wide pelvis, abundant subcutaneous fat, and a shrill voice.

From a biological perspective, women's secondary sexual characteristics are mainly prepared for reproduction. Developed mammary glands facilitate breastfeeding, while a wide pelvis and increased subcutaneous fat facilitate childbirth.

Here is the article: Why waist-to-hip ratio affects height. Please see the big screen

The waist-to-hip ratio causes the center of gravity to change. Women of the same height have a lower center of gravity. In order to adapt to evolution, height will decrease or be delayed (physical content, similar to the relationship between foot size and height and weight)

03. Reproductive selection

First of all, biostatistics is also biology

I will quote some references to illustrate this. Please don’t hit me. I will send you all the references.

Another major reason why women are shorter than men on average is because of reproductive selection: women tend to choose tall men.

Humans tend to choose their partners based on their physical characteristics. This mainly includes the following:

1Facial features (Barber 1995)

2 Waist-to-hip ratio (Singh 1993a,b; Furnham et al. 1997; Henss 2000)

3BMI (Tove´e et al. 1999)

4 Height (Wass et al. 1997).

These traits are associated with reproductive success. Women tend to prefer taller men, but they are generally indifferent to their own height (except for those with extreme heights) (Paw€owski & Kozie€ 2002)

As shown in the figure, the six groups of men and women have different height ratios (male/female) respectively: A = 1.19, B = 1.14, C = 1.09, D = 1.04, E = 1.0, F = 0.96 (Note that height is male vs female, height ratio less than 1 means the female is taller, and greater than 1 means the male is taller!)

So what are these people's height expectations when choosing a spouse?

Height selection preferences of men and women. Circle: average for women; triangle: average for men.

From this set of pictures, we can see that women tend to prefer taller men, while men tend to prefer slightly shorter women.

Continuing with the above picture: From the perspective of male and female height and the duration of marriage, the horizontal axis is the height ratio, and the vertical axis is the duration of marriage relative to the average

It can be seen that in marriage or cohabitation, the taller the woman is than the man (negative value on the horizontal axis), the shorter the marriage will last.

(Female perspective)

(Male perspective)

Explanation: The curves for men and women are slightly different. Women have a range for men's height. It is best if the height ratio is the same or slightly higher, but not too high (z-height drops sharply after 0). Men, on the other hand, think that the taller the man is than the woman, the better (z-height drops slowly after 2).

But the overall trend remains the same: men are taller than women and their marriages last longer

04. Questions about growth hormone

Regarding growth hormone, although there are differences in the secretion of growth hormone between men and women, there is no difference in the overall cycle (that is, the growth cycle of men and women is not much different)

The relationship between growth hormone secretion and age and gender (ZVI ZADIK, 1985)

It has something to do with age, not gender (don’t complain about the picture, this is the original text)

The relationship between growth hormone and age, height, and weight is only related to age. However, during puberty, there are differences.

The difference in growth hormone secretion between boys and girls during puberty: girls have higher secretion of growth hormone at first, but boys have higher secretion of growth hormone later (JD Veldhuis, 1999)

Simple conclusion: There is not enough difference in growth hormone between men and women (conclusions of two papers)

Overall, I think the first reason is more critical, because for mammals that walk upright, the center of gravity of the body has the greatest impact; and the second is the social role, which objectively plays a role in selection.

Finally, this is an era that values ​​appearance, and appearance is valued in every era... What's even more sad is that there is actually literature to support this...

Two more words to add: As a PhD in biology who is not doing his job properly, I like to read books but do not seek to understand them thoroughly, so I read a lot but not in depth. I am against genetic determinism, and any absolute statement is questionable. In fact, regarding height, genes do play a role (for example, by regulating hypothalamic growth hormone, etc.), but it is not absolute. You can increase your height through various ways such as exercise and surgery. In addition, during adolescence when growth hormone secretion is most active, you must strengthen your nutrition.

References are here

DGSP: S 1- Leitlinie Vorsorgeuntersuchung im Sport. 2007

Barber, N. 1995 The evolutionary psychology of physical attractiveness: sexual selection and human morphology. Ethol. Sociobiol. 16, 395–424.

CL Ogden,Mean body weight, height, and body mass index: United States 1960-2002 National Center for Health Statistics (US) - 2004

Furnham, A., Tan, T. & McManus, C. 1997 Waist-to-hip ratio and preferences for body shape: a replication and extension. Pers. Individ. Dif. 22, 539–549.

Henss, R. 2000 Waist-to-hip ratio and female attractiveness. Evidence from photographic stimuli and methodological considerations. Pers. Individ. Dif. 28, 501–513.

JD Veldhuis, JN Roemmich, and AD Rogol 1999 Gender and Sexual Maturation-Dependent Contrasts in the Neuroregulation of Growth Hormone Secretion in Prepubertal and Late Adolescent Males and Females—A General Clinical Research Center-Based Study

Paw€owski, B. & Kozie€, S. 2002 The impact of traits offered in personal advertisements on response rates. Evol. Hum.Behav. 23, 139–149.

Singh, D. 1993a Adaptive significance of female physical attractiveness: role of waist-to-hip ratio. J. Pers. Social Psychol. 65, 293–307.

Singh, D. 1993b Body shape and women's attractiveness. The critical role of waist-to-hip ratio. Hum. Nat. 4, 297–321.

Tove´e, MJ, Maisey, DS, Emery, J. & Cornelissen, PL1999 Visual cues to female physical attractiveness. Proc. R. Soc. Lond. B 266, 211–218. (DOI 10.1098/rspb.1999.0624.)

Wass, P., Waldenstrom, U., Rossner, S. & Hellberg, D. 1997 An android body fat distribution in females impairs the pregnancy rate of in-vitro fertilization embryo transfer. Hum.Reprod. 12, 2057–2060.

ZVI ZADIK, 1985 The Influence of Age on the 24-Hour Integrated Concentration of Growth Hormone in Normal Individuals

The Influence of Age on the 24-Hour Integrated Concentration of Growth Hormone in Normal Individuals: The Journal of Clinical Endocrinology & Metabolism: Vol 60, No 3

If you are interested, you can read these two articles

Women's height, reproductive success and the evolution of sexual dimorphism in modern humans

Variable preferences for sexual dimorphism in height as a strategy for increasing the pool of potential partners in humans