When to start baby on solids

I’ve had mixed opinions about this and just wanted to know what other people think. I’ve heard that earlier than 4 months is bad because their digestive system isn’t fully developed but I’ve also heard that America is the only place that waits until 4-6 months to introduce solids. Also I know doctors recommended waiting until 4-6 months. I personally believe that every mother can make their own decision as to when they want to introduce solids to their baby. Nobody knows a baby better than their mother and if their mother feels they are ready for solids why shouldn’t she try them with solids. If the baby doesn’t take to it then wait a little longer and try again.