Complex sentence: The most likely direct descendants of the Maritime Archaic culture were the Beothuks of Newfoundland who, through European persecution, susceptibility to European disease and a small population base, disappeared in the 19th Century and the Dorset culture, which died out during Inuit expansion.
Split into simpler sentences: The most likely direct descendants of the Maritime Archaic culture were the Beothuks of Newfoundland who, through European persecution, susceptibility to European disease and a small population base, disappeared in the 19th Century. Also, the Dorset culture, which died out during Inuit expansion.