Simplify the following text for a Grade 12 native English-speaking person.
Original: The indigenous peoples of Sikkim consist of the Lepcha , Limbu , migrating from Tibet , Bhutias , descendants of Buddhists who arrived from Nepal in 15th century , who migrated from the Kham district of Tibet in the 14th century , and Nepali , descendants of Hindus who arrived from Nepal in the 19th century .
Simplified: The native Sikkimese consist of the Lepcha , Limbu , migrating from Tibet , Bhutias , descendants of Buddhists who arrived from Nepal in 15th century , who migrated from the Kham district of Tibet in the 14th century .