Samoan rulers. Today, all of Samoa is united under its two principal royal families: the Sā Malietoa of the ancient Malietoa lineage that defeated the Tongans in the 13th century; and the Sā Tupua, Queen Salamasina's descendants and heirs who ruled Samoa in the centuries that followed her reign. Within these two principal lineages are the four highest titles of Samoa - the elder titles of Malietoa and Tupua Tamasese of antiquity and the newer Mata'afa and Tuimalealiifano titles, which rose to prominence in 19th-century wars that preceded the colonial period. These four titles form the apex of the Samoan matai system as it stands today. Contact with Europeans began in the early 18th century. Jacob Roggeveen, a Dutchman, was the first known non-Polynesian to sight the Samoan islands in 1722. This visit was followed by French explorer Louis-Antoine de Bougainville, who named them the Navigator Islands in 1768. Contact was limited before the 1830s, which is when English missionaries, whalers, and traders began arriving. 19th century Visits by American trading and whaling vessels were important in the early economic development of Samoa. The Salem brig Roscoe (Captain Benjamin Vanderford), in October 1821, was the first American trading vessel known to have called, and the Maro (Captain Richard Macy) of Nantucket, in 1824, was the first recorded United States whaler at Samoa. The whalers came for fresh drinking water, firewood and provisions, and later, they recruited local men to serve as crewmen on their ships. The last recorded whaler visitor was the Governor Morton in 1870. Christian missionary work in Samoa began in 1830 when John Williams of the London Missionary Society arrived in Sapapali'i from the Cook Islands and Tahiti. According to Barbara A. West, "The Samoans were also known to engage in 'headhunting', a ritual of war in which a warrior took the head of his slain opponent to give to his leader, thus proving his bravery." In A Footnote to History: Eight Years of Trouble in Samoa (1892), Robert Louis Stevenson details the activities of the great powers battling for influence in Samoa – the United States, Germany and Britain – and the political machinations of the various Samoan factions within their indigenous political system. Even as they descended into ever greater interclan warfare, what most alarmed Stevenson was the Samoans' economic innocence. In 1894, just months before his death, he addressed the island chiefs:There is but