Why you are short and your children are shorter

StephenW

The devolution of man                                                                                    Rachel Browne         March 6, 2011   

                                AUSTRALIANS have spent the past century outstripping their forebears in height because of better nutrition and medical care - but our steady climb up the growth charts may have come to a shuddering halt.
            Australian children born today might be the first generation to be slightly shorter than their parents.
            Many researchers believe that humans in developed countries have reached their maximum height and are starting to plateau, while some are even shrinking. A study in Germany last year showed that in the past 20 years children have become slightly shorter.
                                                         
            Professor Maciej Henneberg, a physical anthropologist from the University of Adelaide who has studied our changing shape, believes it is not in our interests to keep rising ever upwards.
            ''We have reached the point where we cannot keep getting taller,'' he said. ''There are biomechanical limitations of human growth. Being very tall is not ideal.
            ''People who are very tall, they have problems with blood circulation. Excuse the comparison, but they are like giraffes. Giraffes have additional valves in their blood vessels so they can push the blood up to their head, whereas humans don't.
            ''People who are too tall have increased blood pressure, they have problems with circulation, they have problems with co-ordination of movement. It's not that easy to co-ordinate very long limbs.''
            Australian women are two centimetres taller on average than their early-20th-century forebears, while men have grown by four centimetres.
            The English have sprouted at a more dramatic rate, shooting up 10 centimetres in the past century, while the Dutch - world leaders in the loftiness stakes - have sprung up by 15 centimetres.
            Professor Henneberg speculates that Australian children may grow shorter than their parents, and that lifestyle changes are also to blame.
            ''There is much less physical exercise in childhood,'' he said. ''Children are much less mobile. They play less, they watch television more, there is no stimulation for the muscular skeletal system to develop as well as it did in previous generations.
            ''I think that is fairly interesting. It's a modern development.''
            Other scientists, however, believe that as long as living conditions continue to improve, humans will keep reaching new heights.
            Dr Jenny O'Dea, a nutritionist at the University of Sydney who is tracking children's growth as part of ongoing research, believes we will continue to thrive.
            ''We don't really know what the human growth potential is,'' she said. ''It does seem that we're living in the kind of environment that promotes health and growth …  I suspect that we're likely to continue getting taller.''
            She points to better education among expectant women as one reason why birth weights - and the eventual height of children - have increased. Australia's changing ethnic mix is also playing a role in raising the average height.
            ''The other thing which is happening in Australia is the immigration effect,'' she said. ''Pacific Islanders are very tall: the Samoans, Tongans, Fijians and Maoris. There is quite a mix in our children.''
            Professor Stephen Harrap, a specialist in genetic physiology at Melbourne University, said with so many factors involved it was difficult to say conclusively where we are going.  ''It is fascinating to speculate about where we might end up,'' he said.
             ''But height is a complex mix of genetics, nutrition and environment. It's very difficult to predict the future.''