Humans grow slowly because OUR MASSIVE, COMPLEX BRAIN
REQUIRES AN ENORMOUS AMOUNT OF ENERGY TO DEVELOPE !!!
During childhood, brain consumes upto 50 - 60% of total metabolic energy.
Brain needs too much fuel to build neural networks.
Because of this, bodily growth is intentionally slowed down. !!!
For humans, long childhood provides necessary time to learn language, social rules and survival skills.
WHY ANIMALS GROW FASTER ??
Most animals prioritize physical survival and reproduction over abstract intelligence.
For example,
Animals like horses and deers must run within hours of birth to escape predators. This forces rapid physical development over brain's !!!
Thats why, human body simply can not afford to develop a large skeleton and a massive brain, at the same time !!!
Hence our development is longer !!!