Our large brains are good for prediction and problem solving in complex environments... capabilities needed to be a generalist rather than a specialist. Changi

Our large brains are good for prediction and problem solving in complex environments... capabilities needed to be a generalist rather than a specialist. Changing food sources may be part of the picture, but it seems more likely that it'd be a need to utilize more varied and unpredictable food sources, not just a different staple, that'd require these capabilities. It also seems inevitable that there'd have been multiple selection pressures all acting on whatever evolving capabilities we had. Maybe changing food sources upset the status quo, and favored some initial spurt in brain growth, but that in turn would eventually have lead to new social/communication capabilities (and what else?) that would have themselves then acted as differentiators for selection. The story of the selection pressures acting along our evolutionary history is going to be multifacted and messy, ergo any simple explanation is at best incomplete or wrong. Why didn't all animals preying on these larger animals develop large brains? Where are the sabre-tooth developers among us?