Board Thread:General Discussion/@comment-29855659-20170630205901/@comment-31994516-20170711205825

No. Humans didn't have SAVE and LOAD on the surface when they attacked monsters. Timeline manipulation powers are because of causal isolation of the Underground. Frisk/Chara only gain enough power to RESET the surface at the end of the pacifist run, or possibly at the end of neutral.

Note that only the strongest monsters (such as Asgore) can probably defeat an average human one on one given no SAVE powers because of high magical abilities. But most monsters are not like that, being weak, and humans being much stronger on average, because of determination. Strongest monsters were probably just outnumbered and forced to retreat. The surprise factor of the attack may have had some role in this too.

As for other humans, some of them may have figured out how to LOAD when their SOUL is weak, but they never taken a SOUL-shattering hit. Humans in Undertale can survive hits by shielding their body with SOUL power, converting physical damage into spiritual. The primal desire to exist in these fallen humans didn't allow their SOULs to be shattered. In fact, I claim they won't be able to LOAD if their SOUL was shattered, and the only reason Frisk's SOUL shatters and they are able to go back to their SAVE after that is because of Chara being a conceptual determination vessel. Chara and Flowey are both soulless, and that's why they can LOAD on death.