Nothing is not incredible when we talk about human development. Everything began with one cell, growing, and finally end with a completely grown human. However, there are some aspects which differ boys and girls growth, such as the following.
Most important growth takes place during physical development such as height, brain volume, body weight, reproduction system etc. However, not all of them take precisely the same moment or period. For example, brain will grow until you reach 10 while your reproduction system will effectively grow during the purberty.
A research taken in 1996 discovered that most girls will have their maximum body height when they reach 19 while most boys can gain extra height for some years later, but at this point girls will also have completed their maturity, closely related to the reproduction system.
After reaching their full body height potential, girls’ body will grow slowly, but their brain still develop rapidly until it reaches the maturity and adulthood. Another study taken in 1998 discovered that even when the brain does not grow anymore in size, the function will always develop until it reaches adulthood and this applies both for boys and girls. So, there is nothing need to be worried.