Thus, in some island groups, Tangaroa is of great importance as the god of the sea and of fishing. There is often a story of the marriage between Sky and Earth; the New Zealand version, Rangi and Papa, is a union that gives birth to the world and all things in it. There are stories of islands pulled up from the bottom of the sea by a magic fishhook, or thrown down as rocks from heaven. There are stories of voyages, migrations, seductions and battles, as one might expect. Stories about a trickster, Māui, are widely known, as are those about a beautiful goddess/ancestress Hina or Sina who shakes her barkcloth to make lightning, provides fish and sharks to fishermen, brings weaving techniques and sails her boat to the moon.
In addition to these shared themes in the oral tradition, each island group has its own stories of demi-gods and culture heroes, shading gradually into the firmer outlines of remembered history. Often such stories were linked to various geographic or ecological features, which may be described as the petrified remains of the supernatural beings.
An example is provided by genealogies, which exist in multiple and often contradictory versions. The purpose of genealogies in oral societies generally is not to provide a 'true' account, but rather to emphasise the seniority of the ruling chiefly line, and hence its political legitimacy and right to exploit resources of land and the like. If another the ruling line should rise to ascendency, it was necessary to bestow upon the new line the most prestigious line, even if this meant borrowing a few ancestors from the preceding dynasty. Thus each island, each tribe or each clan will have their own version or interpretation of a given narrative cycle.
This process is disrupted when writing becomes the primary means to record and remember the traditions. When missionaries, officials, anthropologists or ethnologists collected and published these accounts, they inevitably changed their nature. By fixing forever on paper what had previously been subject to almost infinite variation, they fixed as the authoritative version an account told by one narrator at a given moment. In New Zealand, the writings of one chief, Wiremu Te Rangikāheke, formed the basis of much of Governor George Grey's Polynesian Mythology, a book which to this day provides the de facto official versions of many of the best-known Māori legends.
Some Polynesians seem to have been aware of the danger and the potential of this new means of expression. Thus as of the mid-19th century, a number of them wrote down their genealogy, the history and the origin of their tribe. These writings, known under the name of "pukapuka whakapapa" (genealogy books, Māori) or in tropical Polynesia as "puta tumu" (origin stories) or "puta tūpuna” (ancestral stories) were jealously guarded by the heads of households. Many disappeared or were destroyed. Thus in the 1890s, Makea Takau, a Rarotongan chief, ordered his tribe to burn all their family books, save his own. As a result, Makea Takau's version became the official history of the chiefly line, removing the possibility of dissent. At his request, extracts were published in the Journal of the Polynesian Society.