Final answer:
The Sinhalese and the Tamils are the two ethnic groups that settled in ancient Sri Lanka; the former brought Buddhism from northern India and the latter are primarily Hindu from southern India.
Step-by-step explanation:
The two main ethnic groups that settled in ancient Sri Lanka were the Sinhalese people and the Tamils. The Sinhalese, hailing from northern India, brought with them Buddhism and the Sinhala language around 2,500 years ago, while the Tamils, whose origins lie in the southern part of India, are primarily Hindu. Historical events have seen Sri Lanka first colonized by European powers such as Portugal, Holland, and subsequently Britain, until gaining independence and renaming itself from Ceylon to Sri Lanka in 1972. These two groups have coexisted on the island with a complex history of ethnic tensions, leading to a civil war that lasted for decades and shaped much of the country's modern political and social landscape.