[time_to_smile]

Because humans (and your language is confusing here between individual humans as models and human society as the model) are constantly receiving new information. Even before humans learned "some berries are bad" they initially thought either "all known eaten berries are bad" or "all known eaten berries are good", then somebody at a good/bad berry and updated their believes (i.e. their model of the world).

Humans learn from other humans because humans don't individually share the same information and model of the world. A science teach can speed up how you learn science by taking the compressed information and explaining it quickly (essentially what is happening in the post), but out scientific model is expanded when we have experiences that call into question the strength of our current model.

However both individually and as a society we are constantly taking in new information (sometimes more sometimes less) and using that to update our model.