science

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


From brutal conflicts to periods of prosperity, pandemics to triumphs for equality, human history is full of highs and lows. But such fluctuations don’t just affect society: the human body can also be a sign of the times.

Studies have shown that our height is not just a matter of genetics but is also influenced by the environment we live in, with key factors including our nutrition and experience of sickness, such as diarrhoea.

According to analysis of skeletal remains by researchers at the University of Oxford, the average height of men in England rose after the Norman conquest, possibly linked to warmer temperatures, but subsequently fluctuated alongside seed shortages and famines, policies to help the poor and changes to the types of work people did and the conditions in which they worked.

In recent decades height has been rising in many but not all countries. In 2016, researchers at Imperial College London revealed that in the 100 years between 1914 and 2014 South Korean women gained more than 20cm in height on average and men and women in the UK gained around 11cm. But the Imperial study also suggested that heights in some countries, including the US, had recently hit a plateau.

Now experts at Statistics Netherlands (CBS), a Dutch government institution, have said that while the Netherlands remains the tallest nation in the world, Dutch women born in 2001 are on average 1.4cm shorter than those born in 1980, while for men the decline is 1cm. So what is going on here?

Prof Majid Ezzati, the chair in global environmental health at Imperial College London, said it would take a few more years to confirm whether the Dutch were indeed seeing a downward trend. But he added: “If this [Dutch trend in height] is real, it’s almost certainly nutrition.”

Ezzati said the Dutch school milk programme was thought to be one reason why the population had grown so tall in recent decades. But changes in nutrition can go both ways – and on-demand food has boomed in recent years. What remains unclear from the Dutch data, says Ezzati, is whether poorer nutrition is limited to particular demographics because of a lack of access to healthier alternatives, or whether the shift is population-wide, reflecting new fashions and social trends.

While migration has been suggested by the CBS to play a role in the latest Dutch data, Ezzati said it was unlikely to be a key factor given the scale of migration to the Netherlands and the size of the change in height.

Genetics is also unlikely to be an explanation. Ezzati noted that this was an important factor in determining an individual’s height – for example, tall parents are likely to have tall offspring – but current data suggests the genes linked to being tall are not restricted to particular populations. What’s more, evolutionary changes would take timescales far larger than a couple of decades to have an effect.

Ezzati said it was crucial to tackle inequalities so that all children could reach their full potential for growth. Indeed, work by his team previously found that while boys and girls in the UK have become taller in recent decades, the rate of increase was not as great as for children in other wealthy countries – a factor they say is down to poor access to nutritious food for those who cannot afford it.

Ezzati suggested that the peak average height for humans was not likely not be reached until the whole population had access to good nutrition, possibly over several generations.

“I suspect that the Dutch have got, on average, at least a little bit more to go,” he added. “[But] whether that’s one or two centimetres or five centimetres on average, I don’t know.”



READ SOURCE

Leave a Reply

This website uses cookies. By continuing to use this site, you accept our use of cookies.