Simplify the following text for a Grade 12 native English-speaking person.
Original: Although peaceful post-conflict behavior had been documented going back to the 1960s , it wasnâ t until 1993 that Rowell made the first explicit mention of reconciliation in feral sheep .
Simplified: Although peaceful , post-conflict behavior had been documented going back to the 1960s , it was not until 1993 that Rowell made the first explicit mention of reconciliation in feral sheep .