In one sense, it's quite wrong to say that the ancient Hawaiian religion is dead. In fact, it's undergoing something of a small revival among certain Hawaiians (although how much of this represents genuine religious conviction and how much reflects resurgent pride in ethnic identity and heritage is unclear). Some Hawaiians still gather at the remaining "heiau" or traditional temples to honor their ancestors and their ancestors' beliefs.
And it's very possible, of course, that the old pre-Christian religion never completely died out. But its dominance definitely ended, decisively, on a specific date.
The "ali'i" or royal class occupied the summit not only of Hawaiian society but of its "kapu" system. (The word "kapu" — related to Tongan and Maori "tapu" and Fijian "tabu" — suggests that something is sacred, holy, forbidden or, as the word has entered English, taboo.) They were thought to possess great "mana" or supernatural power, by which they led their community and presided over offerings to both the gods ("akua") and the spirits of the ancestors (the "aumakua").
The "ali'i" were assisted by the "kahuna," priests or religious specialists who served not only as spiritual counselors but also as political advisers and, sometimes, physicians, artists and master craftsmen.
According to recent scholarship, Polynesian voyagers appear to have arrived at the islands roughly two or three centuries after Christ. By far the most powerful of the Hawaiian chiefs, however, was the relatively recent Kamehameha the Great (1758-1819), who, although he was born in the Big Island's Kohala district, united all of the islands under his rule, thus becoming Hawaii's first king. He is still widely remembered and honored in Hawaii as a man of wisdom and nobility.
The ancient religion remained quite powerful under Kamehameha, and his path to dominion over the islands included such episodes as the 1791 defeat and sacrifice of his rival and cousin Keoua at Kamehameha's impressive, newly built heiau of Pu'uokohola, which looms still today over the seashore to the north of Kailua-Kona and the modern Big Island resorts at Waikoloa.
The kapu system involved a multitude of rules, the violation of which was often punished by death. Such severity was deemed necessary, lest the gods punish the people with famine, earthquakes, tsunamis and volcanic eruptions. But the system's end was rapidly approaching. It may have been hastened by the visits to Hawaii of the British explorer Capt. James Cook in 1778 and 1779. He and his men inadvertently violated many of the taboos but, surprisingly, no disasters followed.
Perhaps this weakened faith in the old religion. Moreover, since compliance with its dictates was burdensome and even oppressive, there may have been pressure to abolish it. Still, while Kamehameha the Great ruled, nobody dared to do so. But Kapihe, a kahuna who was a contemporary of the king, is reputed to have prophesied the humbling of the chiefs and the rising of the commoners as follows:
"The ancient kapu will be abolished;
the heiau and altars will fall;
the islands will be united;
the heavens will descend and the earth ascend."
When Kamehameha died in 1819, his favorite wife, Ka'ahumanu, assumed the role of regent until her own death in 1832. Along with a sister wife, Keopuolani, and the late monarch's successor, Liholiho (Kamehameha II), they abolished the old laws and completely upended the traditional religious order.
How did they do it? They accomplished it via the simple act, in November 1819, of having the new king publicly eat with women — something that had previously been considered both kapu and a capital offense. It was the monarch's role to enforce the traditional taboos. In this case, though, the king was the very person who had flagrantly violated a fundamental kapu. And he and his allies then proceeded to destroy traditional temples all around the Big Island.
His cousin Kekuaokalani challenged this revolution, resorting to war. But the challenger was grievously wounded — and hundreds of warriors on both sides died — at an early 1820 battle that occurred at what is now the south end of Alii Drive in Kailua-Kona. His wife begged that his life be spared; both were summarily executed on the battlefield, and the ancient Hawaiian religion also died that day. The first Christian missionaries to Hawaii arrived only the following month, entering a newly created religious vacuum.
Note: This article draws on "Ancient Sites of Hawai'i" by Van James (Mutual Publishing, Honolulu, rev. ed. 2014) and Andrew Doughty's "Hawaii: The Big Island Revealed" (Wizard Publications, Lihue, 7th ed., 2015).