How much of what we know is learned and how much is inate is a really old question. Do we learn to use our senses and interpret the world from experience, or are we born knowing it? In college I believed we were born nearly a blank slate and that everything we knew was just a matter of applying powerful learning processes to our sensory input. And then a I read a paper:

Imitation of Human and Manual Gestures by Human Neonates

Meltzoff and Moore experimented with making faces at infants [1], looking for imitation. They found it: when the experimenter stuck out their tongue, the baby was more likely than chance to do the same. Which is actually amazing: think about all the steps it takes for them to do this. They need to have a connection between their eyes seeing a change in the experimenter's mouth and activating the muscles in their own mouth in just the right way as to duplicate the gesture. This shattered my previous understanding of neural development, where babies learn how to interpret their senses and move their muscles with lots of practice and experimentation. There is certainly still some of that, but this shows several complex systems are working and connected right after the eyes get their first look at the world.

[1] They later repeated this experiment with newborns under 72 hours old and got similar results. (Imitation in Newborn Infants: Exploring the Range of Gestures Imitated and the Underlying Mechanisms)