Ask A Scientist© Biology Archive

 
Question:  How fast do humans really grow?  And when and why is this their fastest time 
of growth?
ji jim 

Answer:  IF you define fastest in terms of percentage increase in weight or length, the 
fastest growth would be before birth, when a single cell converts into a 7-pound human 
about 18 inches long in only 9 months.  If you define it in actual length or weight per 
time, it is probably during adolescence, maybe between ages 10 and 18.  Before birth, 
growth is partly controlled by the normal mechanisms of development within the fetus, 
with nutrients and raw materials provided by the mother.  After birth, growth is 
determined by a specific hormone, called growth hormone, released by the brain.  
-ProfBill