Todd Mahupuku, of Trentham, asks :-

Over history, how has the average height of humans, both male and female, varied, and what caused these variations?

Bruce Floyd. a biological anthropologist at the University of Auckland, responded.

That is a very interesting, but complex, question. Indirect evidence from things like doorway heights, estimates of stature from human long bones and direct measurements of human height, mostly in the past 200 years, indicate substantial increases in height in some places, but little change in others, and significant declines in average height in a few places. Between the mid-19th century and the end of the 20th, average heights increased by 6 to 19 cm among adult males from various European countries or their colonies worldwide. The smallest increases are in the groups that were initially the tallest. These were mostly descendants of immigrants from the British Isles in the US, Australia, Canada, and New Zealand whose average male heights increased from around 172 to 173 cm to about 177 to 179 cm. A much greater increase is found among Dutch males who were only an average of 165 cm but are now about 184 cm.

While estimates of past female heights are not as good because women were less often measured, changes are likely to be similar. For example, the Dutch female average is now 170.5 cm, making them and their male counterparts the tallest people in the world.

While much remains to be learned about how social processes interact with individual genetics to influence growth outcomes, we are pretty confident that changes in average height documented historically are the result of changes in the quantity and quality of food, disease risk and health care in the first two to three years of life. We potentially grow very quickly then. Eating diets that are insufficient in energy, proteins and vitamins contributes to weaker immune systems so we become ill more easily. When we live in crowded, less sanitary environments our exposure to diseases are greater. Being ill makes us less able to use foods we eat. These influences span across generations; mothers who are better nourished when young are more likely to give birth to healthier babies.

Research suggests that in the 17th to 19th centuries, as Europeans began to explore and colonise many places, they found people who were taller and probably healthier than themselves in some places. These included peoples as dispersed as Native Americans in the central US and Canada, and Polynesians in Remote Oceania. The world continues to change and average heights have shifted recently both up, as among Spanish, Brazilians, Japanese, Taiwanese, Korean, and Chinese, and down as in Guatemala, Bosnia and probably Syria today where civil war makes living much more difficult for many. The most important message is that while we are now learning much more about our genetics and biochemistry related to growth, we need to understand how these fit within humans as socially complex and variable. How we live our lives and influence those of others has implications for how we, and they, grow and develop. I suggest for further reading the book "The Growth of Humanity", B Bogin, Wiley 2001, ISBN: 978-0-471-35448-2