Regarding what age babies absolutely need soid food, I always say
watch the baby not the calendar. It has been my experience that normal
healthy babies typically are developmentally ready for solid food quite a
while before they have to have it nutritionally. If you let them practice
in the developemental stage you won't miss the nutrition stage. If you
wait until they are developmentally ready you save an awful lot of fuss
and work. I think young babies should always be near the family at meal
time for the social interaction . Typical signs of readiness that I look
for is the ability to sit up and reach out and interest in the food.
Then it is time to offer something soft from your own plate. Having teeth
is really not important.
  Our pediatric clinic in town , says start at 4.0 months no matter what.
Some mothers say delay solids until one year no matter what.  Watch the
baby not the calendar.
  Mary Graden