Babies are born with the capacity to understand any language
Infants are born with the capacity to speak and understand any human language. Newborn brains are able to distinguish between any sound in any human language. By 12 months, they are only able to distinguish between the sounds of their native language [1,2].
Medina, John. Brain Rules for Baby: How to Raise a Smart and Happy Child from Zero to Five. Seattle: Pear Press, 2014.
Kuhl, P. K., F.-M. Tsao, and H.-M. Liu. “Foreign-Language Experience in Infancy: Effects of Short-Term Exposure and Social Interaction on Phonetic Learning.” Proceedings of the National Academy of Sciences 100, no. 15 (July 22, 2003): 9096–9101. https://doi.org/10.1073/pnas.1532872100.