Hight it caused by genes. that is well known. im sure if you take the time to search you will find what your looking for. The very fact that a few centuries ago no one was as tall as 7 foot, yet now we have several is proof enough that the genes are changing. That means a small mutations must be occuring.

the evidence of our first ancestors to walk upright, indicated that they were about three feet tall. how does one race get from three feet tall to 7 feet unless genes change.

the more man learns, the more he realises, he really does not know anything.