Why does world’s tallest populace seem to be getting shorter?

Human history has seen many highs and lows, from brutal conflicts to periods that were prosperous, pandemics, to victories for equality, there have been many. These fluctuations are not just a sign that something is wrong with society.
Studies have shown that height is more than just a matter genetics. It is also affected by the environment in which we live, including nutrition and sickness experiences like diarrhoea.

Researchers at the University of Oxford have found that the average height of men in England increased after the Norman conquest. This could be linked to warmer temperatures. However, it also fluctuated with policies to aid the poor, seed shortages and famines as well as changes in the work conditions and types of work people did.

Many countries have seen their heights rise in recent years, but not all. Researchers at Imperial College London discovered that women in South Korea grew more than 20cm on average in height between 1914 and 2014. Women in the UK grew around 11cm over the same period. The Imperial study found that heights in certain countries, including the US had reached a plateau.

Statistics Netherlands (CBS) is a Dutch government agency that has revealed that although the Netherlands is still the largest country in the world, Dutch women born 2001 are 1 cm shorter than men. What is the deal?

Professor Majid Ezzati of Imperial College London's chair in global environment health said that it would take several years to determine if the Dutch are actually experiencing a decline. He said that if this Dutch trend in height is true, it almost certainly has to do with nutrition.

Ezzati stated that the Dutch school milk program was one of the reasons why the population has grown in size over the past decades. However, nutrition changes can be both positive and negative. In recent years, on-demand food has seen a boom. Ezzati says that it is not clear from the Dutch data whether poorer nutrition is restricted to certain demographics due to a lack access to healthier options or whether the shift is widespread and reflects new social trends and fashions.

Ezzati stated that although migration was suggested by CBS as a factor in the Dutch data, it is unlikely due to the magnitude of migration and the large change in height.

It is unlikely that genetics can be a reason. Ezzati pointed out that genetics was an important factor in determining a person's height. For example, tall parents are more likely to have tall children. However, current data shows that genes associated with being tall are not limited to certain populations. Evolutionary changes could take longer than two decades to make an impact.

Ezzati stated that it was vital to address inequalities so all children can reach their full potential. His team found that although both boys and girls have grown taller over the past decade, there was a slower rate for children living in Britain. This could be due to a lack of access to healthy food for those with limited means.

Ezzati stated that humans will not reach their peak height unless all people have access to good nutrition. This could be possible over many generations.

He said that he believes the Dutch have at least a little more to go. I don't know if it is one, two, or five centimetres.