system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why many cultures have developed the practice of carrying large burdens balanced on the head - how is this better than carrying them in the arms?
gpt
It's quite efficient energy wise for the body as the vast majority of the weight is supported by bones instead of muscle exertion.  If you're carrying a heavy load with your arms in front of you, you are using a lot of arm and back muscles to balance.  This could do you harm if done for a long time.  With your bones doing the work you can carry the load a lot farther.  

Another advantage is that the arms are free both for other tasks and for helping with balance.