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Changes in human biology -

Throughout the last century, scientists have tracked much change in terms of human biology through measurable characteristics.

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Impact on biomarkers -

Factors such as changes to environments and nutrition, healthcare access and quality, and other social factors have impacted biomarkers that researchers use to measure change.

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Biomarkers -

Some biomarkers include weight, BMI, height, bone density, waist-to-hip ratio (WHR), reproductive rates (and health), the prevalence of disease, life expectancy rates, and changes to physical structure and features, including differences in skin and hair.

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Analysis in relationship to socio-economic factors -

Biomarkers are measured independently, but analyzed in relationship to socio-economic and environmental factors that have impacted such changes.

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Data analysis -

An international group of researchers has recently conducted a study on a specific set of biomarkers, taking into account data from dozens of countries.

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Over 135,600 samples -

The study, published in the journal Biology Letters, analyzed over 135,600 heights and weights recorded from males and females around the world.

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We're growing -

In many ways, due to nutritional improvements, human beings have literally grown. Yet, the study shows that there is a discrepancy between the growth rates between males and females.

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Males growing more -

Males have grown both taller and heavier at a greater rate than females. In fact, according to the study, the male growth rate is twice that of the female rate. 

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Data via WHO -

The data, provided by the World Health Organization (WHO), was collected from 69 countries and analyzed by researchers in Europe and North America.

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Analysis in conjunction with HDI -

Researchers used the WHO data in conjunction with the Human Development Index (HDI), which seeks to measure overall well-being, taking into account life expectancy and per capita income, among other factors.

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Difference in height increases -

The study found that women's heights increased by just over half an inch (1.68 centimeters), while men's heights increased by 1.59 inches (over four centimeters).

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Difference in weight increases -

In terms of weight, the study found that females are now just under six pounds heavier (2.7 kilograms), as opposed to males, who have gained approximately 14 pounds (nearly 6.5 kilograms).

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Explicit conclusions -

One of the less surprising but nonetheless explicit conclusions that the study underlines is that as living conditions improve, height and weight increase.

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Earlier study -

In comparison to an earlier study conducted on data collected in the United Kingdom during the first half of the 20th century, as living conditions improved across the region, jumps in height also accompanied these improvements.

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UK statistics -

From 1900-1950, women’s heights increased by 1.9%, while men’s jumped a whopping 4%. This means, interestingly, that in the UK, 25% of females born at the turn of the century were taller than the average males, yet just 50 years later, this percentage dropped to 12.5%.

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Males benefit biologically -

As access to resources increases, males tend to, at the very least, biologically benefit more than females. Accordingly, when resources decrease and there is some sort of scarcity, males tend to be more disadvantaged than females.

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Males are more vulnerable to environment -

Researchers argue that metabolically, males are more “active” in comparison to females, which means that they are also more vulnerable to environmental influences.

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Disease burden -

This means that when a stressful environment emerges, men's size is affected more than women's because they also carry a greater rate of “disease burden.”

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Taller people face greater cancer risks -

Interestingly, an increase in height does not mean that males are in any way less prone to disease in general. In fact, taller people are more vulnerable to several cancers. This is said to be due to a greater amount of cells that can mutate.

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Reproduction demands -

For females, the study is also consistent with the belief that reproduction demands produce ecological constraints, particularly due to the expenditure of energy required to sustain pregnancy and facilitate nursing.

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Growth spurt -

The study argues that the growth spurt is beyond just access to more nutritious food and other improvements to quality of life.

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Sexual selection -

So what else is driving this change? Sexual selection. Researchers found that the difference between growth rates comes down to how we choose our partners in heterosexual relationships.

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Women prefer tall men -

The study shows that women tend to prefer taller men—meaning that men's heights are a marker of attractiveness. In contrast, men, generally, don’t place great importance on women's heights.

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Men's morphology -

Researchers propose that women are more likely to select a partner who is not only taller but also muscular, meaning that men's morphology may actually be more “sensitive to the environment” than women. This is referred to as differentiation in sexual size dimorphism (SSD).

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Resiliency -

Researchers argue that the perception of larger men is that they are “well-made,” referring to some sort of resiliency in terms of health and vitality. In addition, there is also the perception of the capacity to “protect and defend” their families.

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Not necessarily muscle -

However, the study does note that the increase in weight doesn’t necessarily point to greater muscle mass in males, regardless of the trend observed in sexual selection.

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Correlation not causation -

This correlation is just that: a correlation. There is insufficient data to assert a definitive cause-and-effect relationship between gains in growth and the SSD.

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Fascinating study -

The fascinating study certainly provides a great collection of data on how biomarkers are changing with various socio-economic improvements.

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Reflections -

The analysis that the study provides, while not necessarily causation-conclusive, offers some interesting points to reflect on.

Sources: (The Guardian) (CNN) (Science Alert)

See also: Common health mistakes you might be overlooking

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