What is the evidence that environmental factors impact height?
Professor Peter Visscher, an expert in genetics from Queensland University in Australia, says, “There is a lot of evidence that height increases over time when countries industrialize and/or get wealthier, and this change must be environmental because genetic factors don’t change over short periods of time (e.g. decades).”
He goes on to say that “the likely specific environmental factors are abundance of food and better healthcare.”
Multiple case studies have highlighted how diet affects height. Professor Saverio Alberti, an expert in genetics from Messina University in Italy, says, “An example that may fit is the height of newborns during the 1944 famine in the Netherlands.”
Children who were born or grew up during this famine were about 4cm shorter than the average Dutch height of the time.
What role does genetics play?
It is generally accepted that about 80 percent of height is influenced by genetics. Your DNA determines your maximum potential height, whilst environmental factors determine whether you reach this maximum or not.
For this reason, it difficult to predict heights from genetics alone in countries where malnutrition is prevalent in children. On the other hand, in countries with adequate nutrition, it is possible to predict height using genes to the nearest 3cm.
How tall can we get?
It is likely that there is a maximum physiological height that we can reach, over which our heart would not be able to pump blood around the body effectively. It has been postulated that the limit might be around 2.7m, which is the height of the tallest person ever, Robert Wadlow.
Global average height has increased steadily over hundreds of years, but plateaued around 30 years ago, does this mean we have reached our maximum height?
Dr Eirini Marouli, an expert in genetics and statistics from Queen Mary University in London, says, “It is reasonable to assume that there is an upper limit to average height, at which nutritional and health factors are optimal. But it has also been hypothesized that recent lifestyle changes may be hindering further changes in the average height of humans.
“So, additional factors influencing height could include changes in healthcare, nutrition, and socioeconomic status. Could height have reached its limit? Only time can actually tell.”
Whilst height is primarily determined by genetics, environmental factors such as diet also play a significant role.