If you mean those jars of mushed up fruit, they used mushed up fruit.

If you mean formula, then they either had a wet nurse who could assist, or the baby would die.

Infant mortality has decreased significantly in the modern age, and it’s the main reason average life expectancy has gone up so much.

True /s

How high are you rn?

Titties.

must of

Must have, or must’ve. Of is a preposition, not a verb.

If the post is not a joke, your grammar definitely is

Women breastfed for far longer, up to 6 years, and they still do in some parts of the world.