And bilingual newborns can distinguish between the two languages. It's not just one big language with both sets of sounds for them; it's two separate languages for them, too. The way they tested that part was to have someone speak in English until the kid lost interest and then either switched to a different speaker or the same speaker in Tagalog. The kids showed increased interest in the different language but not the different speaker.
Babies' brains really are learning machines, and it starts before birth.