Question

how would be the human life if there is no
second brain is
in their body

Answer 1

There is a superhighway between the brain and GI system that holds great sway overhumans ... This mind-gut connection is not just metaphorical. ... The enteric nervous system is so extensive that it can operate as an independent entity without input from our central nervous system

Answer 2

If our second brain was'nt there then our life would be really devasted.
We cannot react to stimulus faster than with second brain and therefore get many injuries.