Each baby is wants nutrition food: some may need food other than breast milk or infant formula sooner than others, and as there is no Baby Food Pyramid, it is hard to tell the nutritional requirements of any given baby.
Babies typically move to consuming baby food once nursing or formula is not sufficient for the child's appetite. Babies do not need to have teeth to transition to eating solid foods.
Teeth, however, normally do being to show up at this age.