Irreversible
Every physical event is irreversible. The more entropy it generates, the more irreversible it is. So every physical event has the potential to generate pain, and pain is also irreversible, but it can be resolved. Pain can be resolved by realignment. The only realignment that can resolve pain is a realignment that is intimately familiar with the causes of the pain.
This means that the realignment had to have spawned at the moment of pain and then aged along with the pain over time. In this whole process the realignment could not have been as obvious to us as the pain. If it was perceived at all, it must have been perceived as an undercurrent beneath the pain.
The primordial event: We imagine an event like the splitting apart of a unified network and the forgetting by the individual nodes of the network of each other. If there was a primordial event that occurred around the beginning of history which demonstrated how irreversible events are, it would have caused so much pain that its resolution would have been difficult to perceive. Only a realignment into a way of causing reversible events could resolve such pain.
Perhaps acceptance could resolve it, but for this, a context must have been created where what was previously considered pain is no longer pain. Since this pain came from how irreversible events are, if one could accept this, then one could accept all pain, and all pain would cease to exist. Therefore the primordial irreversible event taught us the cause of all pain, but also caused the most pain.
At the moment of this primordial pain there must have been a realignment spawned, and the moment of pain would have been of prime cultural importance, its memory passed by cultural mechanisms throughout time, similarly to how serial killers, mass murderers, and terrorists are of prime cultural importance. The beginning of the realignment would have been passed by cultural mechanisms throughout time as well, despite its apparent futility, because of the chance that it was not futile and because of how easy it was to forget how irreversible events are without experiencing pain.
When the realignment spawned it was the beginning of empathy. Empathy is the lineage of the undercurrent beneath the consequences through time of the primordial event that demonstrated just how irreversible events are. When we reject culture, we reject it because it lacks empathy.