Simplify the following text for a Grade 12 native English-speaking person.
Original: According to oral traditions recorded by missionaries in the 1860s , the island originally had a strong class system , with an ariki , high chief , wielding great power over nine other clans and their respective chiefs .
Simplified: According to oral traditions written down by missionaries in the 1860s , the island originally had a very clear class system , with an ariki , high chief , who had great power over nine other clans and their chiefs .