Board Thread:Speculation House/@comment-14138255-20141017020106/@comment-25411051-20141018222245

Younger Grimm stay closer to humans, they don't know to resist the call of negative emotions. Most are killed the ones aren't killed wise up, learn to resist the call of negative emotions, move to more isolated locations and wait. During this waiting they grow stronger and grow the bone plates.

This happens on an individual basis. The individual learns not the group or the next generation. According to Oobleck there is no upper age limit to Grimm. So the longer the individual lives the more that individual learns.

My opinion