Genetic factors are the decisive factors to control people's height. Specifically, it is genetic genes that control human height. It is a macromolecular chemical substance, which exists on chromosomes in the nucleus and is called deoxyribonucleic acid. This genetic material is passed down from generation to generation through germ cells.
There are about 5 million genes in the human body, and all organs, as well as their appearance, characteristics, height, body shape, eye size, nose bridge, eyelids and eyelashes are controlled by genes.
There are many pairs of genes that control human height. The more high genes in the body, the higher people will grow. Short people, mainly because parents don't give more high genes, on the contrary, short genes are more than enough.
However, genes are only the basis of heredity, and environmental factors, especially nutritional status, lifestyle and working conditions, also play a great role. For example, Swedes have increased their height by an average of 9 cm in the past 100 years, which is the result of the general improvement of their nutritional status and working conditions. During the thirty or forty years from 1892- 1926, the average height of Japanese people increased by three centimeters, which was mainly the result of their changing their living habits from sitting cross-legged to sitting in chairs.
The younger generation in China is generally taller than their parents, which also shows that environmental factors and living conditions have a great influence on people's height.