This photograph shows soldiers of the Eight nations alliance in 1900. British and also American soldiers are taller than continental European and Asian soldiers. Left-to-right: Britain, United States, Australian, British India, Germany, France, Austria-Hungary, Italy, Japan.
Photo taken from: http://www.sci-news.com/othersciences/anthropology/science-european-men-01355.html
For the last two decades of my interactions with Europeans and Americans, one topic often come out of the talk is the height of the ‘Westerners’ vs. the Asians. I never truly understand why there is such a height difference until I was visiting the Rembrandt House in Amsterdam some years ago. I went inside the bedroom of Rembrandt and thought that I entered the wrong bedroom due to children size of the bed. I read the text on the sign carefully and found indeed it was the bedroom of Rembrandt. Rembrandt Harmenszoon van Rijn  was a Dutch painter and etcher, and one of greatest in the history of Europe. He was born in 1606 and died in 1669. One of my Dutch colleague who has been to one of the Dutch palaces recalled too the small size of the bed in the royal bedroom. Fast forward 350 years, now the average height of the male Dutch is 185 cm, and is the tallest in the World, in stark contrast to their once being of the shortest Europeans.
Figure 1: Median male (military) height for various countries between 1820 and 2013. Note that even during the first and second World War, the deterioration of the living environments did not deter the growth of average height of people in Europe and the US.
Dutch has become the tallest only recently
Let us go back to the first half of the 18th century, the economist John Komlos and Francesco Cinnirella  found that the average height of an English male was 165 cm (5 ft 5 in), and the average height of an Irish male was 168 cm (5 ft 6 in). The estimated mean height of English, German, and Scottish soldiers was 163.6 cm – 165.9 cm (5 ft 4.4 in – 5 ft 5.3 in) for the period as a whole, while that of Irish was 167.9 cm (5 ft 6.1 in). The average height of male slaves and convicts in North America was 171 cm (5 ft 7 in). American-born colonial soldiers of the late 1770s were on average more than 7.6 cm (3 inches) taller than their English counterparts who served in Royal Marines at the same time. Figure 1 reveals that the Dutch became the tallest human on Earth only recently in 1980s. It is still a puzzle that the tremendous increase in height of American-born colonial soldiers and even the slaves and convicts are taller than their European counterparts which predated the use of any drugs on livestock (as will be mentioned later).
Natural Selection, wealth, nutrition?
There are many theories about why the Dutch has become the tallest people, among them are natural selection (meaning taller men get more attention from female and have more offspring, however this is only true in the Netherlands but not in the US) and the environments according to one study . Others have attributed the reasons to genes (that the Dutch genes is supposedly to produce taller Dutch in prehistoric period), wealth and nutrition . However, these reasons are far from convincing. For example, this would mean the male slaves and convicts in North America has more offspring than the Europeans, and that they were richer than most Europeans and having more nutrition than them as in the study of John Komlos and Francesco Cinnirella.
Diet and modern food production
One particular aspect that the research studies on height have consistently underestimate is the difference in diet between the Europeans and Asians. For most part of Asia, such as in Vietnam, southern part of China, Japan, Korea, and South East Asia countries, the traditional diet of the people are rice, vegetables and fish, and chicken, and these are very different from modern Europeans and Americans on meats and dairy products that are heavily produced by modern industrialize scale processes. Often these processes used different kind of drugs such as the growth hormones to speed up the growth rate of livestock or to prolong dairy productions. The FDA in US approved a number of steroid hormone drugs for use in beef cattle and sheep in the 1950s , which indicated that the use of growth hormones could be predated that. Since then there are hundreds type of drugs and antibiotic being used on livestock across the world, particularly in the U.S. and in Europe. A study in 2009 found that the level of antibiotic measured in streams, lakes and well water near pharmaceutical factories in India are 10,000 to 100, 000 times higher than levels measured in sewage effluent in the US or China . These pharmaceutical factories are producing most of the drugs needed in the world.
Figure 2: The average height of Japanese students at the age of 17 .
Figure 2 shows the change in height of Japanese students at the age of 17 as documented by the Japanese government since 1900. Japan is much ahead of the rest of Asia in industrialization, during the period from 1900 to 1950s, there is a shift in the diet of rice/vegetable/fish based food to a more Western modern diet. For example, in 1947 (just after the World War II that the Japanese has surrendered and Japan was in the stage of building up after the war) average Tokyoite consumed a modest 5 grams of meat per day, and increased to 90 grams per day now . We should note that even though there is a shift into western modern diet, most Asians still stick to their traditional food and diet.
In recent decades, due to the fast development of China’s economy, the average height of Chinese also increased especially in the cities where meat and modern diet has become popular. Traditional diet in the Northern China (more meat based and dairy such as from sheep, horse, and cow) is different from Southern China, and this is manifested in the average height of people in cities in these two regions where the people of northern regions tend to be taller than the people of southern regions. In more developed cities such as Beijing (175 cm) and Shanghai (174 cm), the height of people is also among the tallest in China regardless of the regions.
Figure 3: Average height of Chinese men and women by province .
Figure 4: Average height of male and female by country in ASEAN .
Singapore is the most developed city in the South East Asia, the inhabitants are immigrants from Asia countries such as China, India, Indonesia, Malaysia, and some Caucasians. The city state diet is also slowly shifted to modern Western diet. Now the height of average male and female is the tallest in ASEAN at 171 cm and 160 cm, respectively (Fig. 4).
The ghost of gene superiority lives on
My interactions with fellow researchers especially those of biology or life sciences backgrounds is even more disappointing given that they are equipped with more knowledge on genetic and epigenetics than people of other fields and backgrounds. I still hear a lot of people telling me that it is genes that determine the height of people of different regions. This is not totally true that everything is related to genes alone. A lot of recent studies have indicated epigenetics is much more complicated than the level of knowledge currently we possessed. Epigentics is the studies about the change in gene expression, e.g. due to environmental influences. Let’s say the DNA is the stored information about building a house (including everything inside the house), the secondary, tertiary and higher structures of DNA (i.e. the formation of double helix DNA and the folding of multiple DNA strands) is related to a set of things and its dimensions in the house at certain circumstance or environment. In the nucleus of a cell where DNAs are packed densely into different ‘modules’ which is called the chromosomes in the scientific term, these modules are not totally isolated from each other in terms of their ‘functions’. Currently the studies of interactions of these adjacent ‘modules’ are very limited and the understanding is vague due to technical difficulties using current technology. Environments, i.e. the place where people live, the contamination, the drugs, the diet etc., will have different epigenetic effects. Meaning that the size of the house, the things inside and their dimensions would not be the same permanently, as in the metaphor example given here.
Where are the human heading to?
The European Industrial Revolution started from around 1760, one hundred years after the death of Rembrandt. Only in the 1870s that the Japanese has started its own industrial revolution during the Meiji period . Other Asian countries only started its own Industrial Revolution at a much later period. These has changed the way we live, eat, and the environment we are dependent on. Many rivers and lakes where we are depending for our drinking water are contaminated at high levels of all kinds of drugs we used in livestock, plantation or other purposes  .
The change in diet, the modern processed food with all kinds of natural and unnatural additives, the use of drugs, antibiotic, our contaminated environments all would contribute to the change in epigenetic effect in human gene. Not only the height will change, different parts like the size of our feet, palms, bones, our reproductive organs (especially for male, as reported in the use of BPA in plastic bottles) etc., will be altered too due to epigenetic changes. A study also relates the height of people to their life span in which shorter people in general lives longer than their taller counterpart by 5-7 years . The rising of different kind of cancers could also be correlated to modern diet and even to the height of people in which taller people are more prompt to get cancer  .
When I look around at the older generations of Asian origin in Singapore, those who are born in the early 20th century often with height from 140 cm -160 cm, with some outliers. Then I look at the next generations, particularly my nephews, they are again much taller than the older generations, with height from 175 cm -185 cm. My height is 170 cm, about 10 cm taller than both of my parents who were born in the 1930s. I feel there is something not right. When I was a baby, our family could hardly get any good quality milk powder. I still remember the first time I was drinking ‘fresh’ milk and that was given to me for free during my primary school time in the 1980s. Imagine how late Malaysia and Singapore are behind the Europe in making the milk to become popular (well may be a good thing given that dairy products have many drawbacks). We cannot attribute all these changes to gene alone, because both parents of a tall kid often are not tall at all. We might want to try the theory of some scientists and to attribute them to their prehistoric ancestor, which probably mixed with the Dutch gene!
My nephew with height of about 180 cm has trained to be a body builder. However, there was one time he had a dislocation at his arm which could be attributed to excessive muscle building. I met another bodybuilder that had the problem of slipped disc. The common chronic conditions for Dutch includes arthrosis, back problems, neck or shoulder problems  . This indicates that our body has a limit to withstand the increase in bone and muscle mass as determine by our human ‘genes’ regardless of our race. The epigenetic expression however will be determined by the factors of the environments. In particular, the epigenetic effect is most easily influenced during our growth period from early baby to the juvenile periods. All these pointed to a range of complicated interactions of human health, body, and mental state with our environment and diet. It is very naive for most of us, unfortunately including many scientist of biological backgrounds to ignore these ‘evidences’. We choose to believe blindly gene determine everything except may be the intelligent as a step forward from Immanuel Kant, a German scientist who proposed that the superiority of race based on genes.
 Wikipedia: Rembrandt
 Wikipedia: Human Height
 Did natural selection make the Dutch the tallest people on the planet? (2015)
 Why Are the Dutch So Tall? (2014)
 Steroid Hormone Implants Used for Growth in Food-Producing Animals
 Unprecedented levels of antibiotics pollute India’s water (2009)
 Trend of the average height of Japanese men