A century ago, humans were quite short. For example, the average South Korean woman was about 4-foot-7, or 142 centimeters, while the average American woman was about 5-foot-2, or 159 centimeters. Humans were fairly short by today’s standards, and that was true throughout nearly all of human history.

But in the past century, human heights have skyrocketed. Globally, humans grew an average of about 3 inches, but in South Korea, women grew an astounding 8 inches and men grew 6 inches on average. So what exactly happened?

Researchers have tried to pinpoint how much of human height can be attributed to genetics, and how much of it is swayed by our environment. One study of British and Welsh World War I soldiers found that growing up in an environment with better nutrition and less disease led to noticeable height differences in adulthood. Later, researchers started studying siblings and twins and found that about 20 percent of their height differences can be attributed to their environment.

Genetics determine how tall we can potentially get during puberty, but throughout most of human history, that growth was stunted. In the past 100 years, though, the average human has had significantly better nutrition and health. In turn, we got taller.

South Korea is a unique example. In the early part of the 20th century, South Korea was a poor and hungry country. But drastic economic growth fueled improved living conditions:

• The country’s GDP per capita went from around $158 in 1960 to about $35,000 in 2021, according to World Bank data — in line with affluent European countries.
• The country’s food supply was about ​​2,100 calories per person in 1961, in line with the average low-income country. By 2013, each person had about 1,200 additional calories available, according to data from the UN’s Food and Agriculture Organization.
• UN data also shows us that more than 20 percent of South Korean infants died before age 1 in 1950, but now it’s about 0.2 percent.

However, South Korea’s improved living conditions are a harsh contrast to North Korea. For half of the 20th century, the south and north were one country. Heights in those two regions were nearly identical. So what happened to human height in North Korea after an authoritarian regime took over and closed off its borders?

More reading:

• A Farewell to Alms: A Brief Economic History of the World, by economist Gregory Clark, beautifully connects economic conditions to human living conditions.
• This Scientific American article by molecular biologist Chao-Qiang Lai breaks down the research on how much of human height can be attributed to genetics and how much is environmental.
• The UN’s Food and Agriculture Organization has some of my favorite data sets. Understanding what humans eat — and how that’s changed over time — gives us insights into everything from economics to biodiversity.
• There are many data sets on human heights over time, but the one I used in this video is from the NCD Risk Factor Collaboration.

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