At birth, height can be predicted to be within a few centimeters.
People of various heights populate the world, so why are some adults short while others are as tall as professional basketball players?
Researchers looking for the answer have found it broadly relates to genes. Indeed, studies looking for metrics and variables that can be used to predict a person's height have found that genetics is a powerful indicator.
In other words, people with tall parents will likely also need to pay for extra legroom on a flight. But there's another important consideration: This assumes that you didn't experience some severe hardship in your early years. Studies have shown that malnourishment and severe disease during childhood can prevent them from reaching their genetic height potential.
These hardships can even affect average changes in height across entire countries. In a 2016 study in the journal eLife, carried out by researchers from Imperial College London, analyses showed that the world's tallest men come from the Netherlands and the world's tallest women hail from Latvia. But this league table wasn't always this way, according to the international Non-Communicable Diseases Risk Factor Collaboration (NCD-RISC).
South Korea was 133rd in the 1985 rankings, but by 2019, it had jumped to 60th place. The leading theory among scientists, at least, is that this boost may be due to improved diets resulting from South Korea's development in recent decades.
"In South Korea and the People's Republic of China, it's widely understood that increasing height over the last one to two generations is largely due to improved nutrition," said Stephen Hsu, a professor of computational mathematics, science, and engineering at Michigan State University whose research has looked at predicting a person's height. "Protein and calcium and total calorie intake have all gone up a lot during that time."
Meanwhile, other countries have fallen on the NCD-risk list. In 1985, for example, the United States was the 38th-tallest country globally, but in 2019, it dropped to 58th place. Is that because the government has experienced immigration from other countries where people are smaller on average? And in that case, is it all about genetics? That's likely one main factor, but not the only one, He said.
"Aside from immigration, some people hypothesize that the quality of nutrition for everyone has gone down with the increased consumption of fast food, soft drinks, etc.," he said. It could also just be that other countries are edging out the U.S. In other words, Americans aren't necessarily getting shorter; they're just not growing as fast as people in other nations.
Poor nutrition isn't the only environmental factor that can affect a person's stature. Serious diseases can also negatively impact growth, mainly if they occur in childhood; celiac disease, bone disease, such as rickets and juvenile osteoporosis, and anemia are all examples.
Although an unhealthy diet and severe illness in childhood can lead to a shorter stature, research suggests that genetic coding is far more influential.
In a 2018 study published in the journal Genetics, Hsu showcased the importance of genes in determining height. Along with colleagues, he used machine learning and computer algorithms to analyze close to half a million genomes of people living in the United Kingdom. After crunching the numbers, the team could accurately predict a person's height and bone density from just their genes.
Moreover, genetic mutations and hormonal imbalances have also been linked to short stature, including dwarfism, a condition in which a person stands at 4 feet, 10 inches (147 centimeters) tall or more petite. Dwarfism can be split into two subtypes. First, there's what is known as disproportionate dwarfism, which is when some parts of the body are small, but others are either of average or above-average size. The other type is proportionate dwarfism, in which all body parts are proportionately smaller than average. According to Stanford at The Tech, both types of dwarfism are genetic, and there are 200 or so genetic variations that can end up causing the two forms. Some of these genes are genetically dominant, meaning a person needs to inherit the genes from only one parent. In contrast, others are genetically recessive, meaning a person needs to inherit the genes from both parents.
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