Roughly 200 separate groups speaking distinct languages live around the Sepik River. As might be expected, the variety of artistic styles found among these groups is bewildering, but three visual elements seem to be basic to nearly all the styles in varying degrees: (1) designs in which two triangular forms are connected at their bases or apexes, often with further design elements in the angles so formed, (2) sculpture based on vertical series of hooklike forms that can be either unidirectional or in opposed groups, and (3) naturalistic representation of natural objects. The interplay of these three elements in various styles suggests that the first two elements preceded the third. The Sepik areas treated in this discussion are, moving clockwise, the northwestern coast, the central coast, the eastern coast, the southern tributaries, the South Sepik Hills, and the upper Sepik.

The styles of the northwestern Sepik area are closely related to those of its western neighbour, the Humboldt-Sentani area. Forked-tailed zoomorphs, used on canoe prows and paddles, and pyramidal houses are common in both regions. The art of the northwestern Sepik groups, however, is based predominantly on the triangular design described above. Sculpted figures are rare in the area. The most conspicuous works are shields, which show many variants of the triangular design. Among the Olo tribe, for example, the triangles are formed from a group of scrolls. Triangular designs can also be found painted on bark sheets used by various groups for initiations and on huge conical masks used by several groups in healing rituals. The Telefomin carved the designs onto tall boards used as house entrances. Similar boards were used to create whole facades by neighbouring tribes. Some tribes used the triangular motif in conjunction with an S-shaped double-spiral design on tobacco pipes, hand drums, and bark paintings.

The north-central section of the Sepik region stretches from the coast to Lake Chambri just south of the Sepik River. The major groups in the area are the Boiken, the Abelam, and the Sawos and the Iatmul.

The Boiken styles, which appear to have been numerous, are relatively little known. Their most conspicuous monuments are the ceremonial houses, which follow on a smaller scale the pattern of Abelam houses to the west. Masks of the coastal Boiken were in a long-nosed style; others were made in basketry. Basketry was also used for a variety of small masks, bird figures, and abstract forms that were attached to large turbo shells used as valuables. Figure sculpture was rare, but the Boiken had rich traditions of pottery making. Food and cooking pots were elaborately decorated with engraved designs and were widely distributed, especially to the river people.

The art of the Abelam tribe, which lived in the Prince Alexander Mountains, was tied to a vigorous ceremonial life. It thus presents a far more spectacular scene. Their pyramidal ceremonial houses, centres for cults of yam growing and initiation, were built on the grandest scale known in New Guinea. They featured vast painted gables and lintels, to which carvings of hornbills, parrots, and lizards were attached. The carvings were in every instance augmented by paint, which indeed the Abelam considered magical in itself.

There are three basic styles of Abelam sculpture. The figure sculpture of the north consists of simple, bulbous forms in massive but sketchy conformations, with detail largely supplied by painting in yellow, black, and white over a predominantly red ground. The eastern style is now similar to that of the north, although somewhat less dependent on polychromy. At an earlier period, the eastern sculptures were elongated, with a human head at one end and the rest of the figure consisting of clusters of bird heads. In both the north and east, major sculptures were often monumental in scale, some 20 feet long. Large openwork panels were also carved, showing humans, animals, and birds. Figures in the southern, or Wosera, style are generally standing; they have ovoid heads that are often surmounted by birds.

Painting styles also varied. Bark paintings found on the ceremonial house gables of the northern Abelam are broad, large-scale depictions of spirit faces, figures, and animals. Paintings by the southern Abelam tend to be smaller in scale and painted not in flat areas of colour but with much fine line and cross-hatching.

Masks, which were worn for initiations, were generally confined to basketry hoods with elaborate openwork eye panels and noses. Small basketry masks were attached to yams during rituals, and men wore pointed basketry crests as hair ornaments. This pointed form was repeated among the Wosera on a huge scale as a ritual headpiece made of feathers.

The Abelam made a wide range of small decorated objects, including cups, spoons, whistles, and spinning tops in coconut shell; arm ornaments, daggers, and gouges in bone; spears, digging sticks, hand drums, and stirrers in wood; and pots in clay. All were incised with human faces or with closely spaced, complicated designs incorporating the typical Abelam scroll and oval patterns.

The Sawos and the river-dwelling Iatmul, who historically derive from the Sawos, worked in styles totally different from those of the people to the north. Their ceremonial houses were long rectangular structures, with upper stories elevated on posts often carved with ancestral faces and figures. The gables were not of exaggerated size but had masks in wood or basketry. King posts, which had female figures carved at their bases, extended high above the house roofs and were topped with carvings of human beings grasped by eagles.

Human-figure sculpture was a major theme in Iatmul and Sawos art. Human figures and faces and a wealth of curvilinear ornament adorned numerous sacred objects, including flutes, slit gongs, trumpets, drums, and an array of less familiar musical instruments that simulated the voices of spirits. They were also to be found on such mundane equipment as stools, headrests, bowls, palettes, tools, weapons, and canoes. As a rule the figures were naturalistic within the limits of certain standard conventions, which varied between the eastern (Parambei) and the western (Nyaura) Iatmul. The figures of the east tended to be more gracile than those of the west, which were frequently stocky and burly. The profiles of faces on eastern Iatmul figures often had a graceful S-curve, while those from western Iatmul and the Sawos had heavy jaws, high cheekbones, and sunken eyes under horizontal brows. These same features characterized the long-nosed wooden mei masks of the Iatmul. Other types of masks, however, represented mythological birds, crocodiles, fish, and other animals. These were generally constructed of basketry and painted bark and were often of great size.

Perhaps the most striking material used in Iatmul-Sawos art was human skulls. These enthusiastic headhunters covered the skulls of victims and ancestors with clay and painted them in the patterns used in life. The skulls were then displayed on racks made of painted bark sheets or were mounted on puppets for use at initiations and funerary ceremonies.

In the far-eastern section of the Sepik region, around the Ramu River, the peoples living along the coast and on offshore islands engaged in extensive cultural exchanges, trading dances, masks, slit gongs, and carvings. The Murik people at the mouth of the Sepik River were particularly active in this regard. Tribal styles thus spread widely. In some areas local styles incorporated or were supplanted by imported styles, but in many localities a multitude of distinct styles existed side by side.

Although styles vary, most figure sculpture from the eastern Sepik depicts standing males (females exist but are unusual). The figures range in size from miniature to larger than life. They have ovoid heads that droop forward and limbs that are slightly flexed. Some are fitted with actual human skulls. Both figures and masks frequently feature enormously exaggerated noses, which signify masculinity (females have short noses). Besides ritual objects, a wide range of utilitarian equipment, from canoe prows to bowls, was decorated with carved representations of humans, birds, and animals. The carvings were often augmented by the tight geometric patterning that was characteristic of Murik art in particular.

Through the flat, swampy country west of the eastern coastal hills, several tributaries flow northward to the lower Sepik, each associated with a particular artistic style. These rivers are, from east to west, the Porapora, the Keram, and the Yuat. The art of the Porapora area is related to lower Ramu styles but is less elaborate and profuse. Ceremonial house posts were carved with figures in a plain, almost geometric style—a style that was also used in carving stafflike figures with dishlike receptacles for ancestral skulls.

The Kambot tribe of the Keram River, on the other hand, combined sculpture and painting in complex, ambitious designs to decorate their ceremonial houses. The houses’ long, horizontal gables were filled with painted compositions of an ancestral hero with his wives and animals. Paintings also adorned the interiors, and the gable painting was often replicated on a grand scale in feather mosaics on wood slabs—a unique technique in the Sepik. Sacred objects included large panels of basketry that had human skulls attached and were decorated with clay, shells, and boar tusks. Small versions of the panels were attached to sacred flutes. Wood carvings included rectangular shields, which were engraved and painted, and small-featured hemispheric or oval masks. Huge figures of crocodiles were constructed of painted bark sheets for initiations.

The Yuat River people, especially the Biwat (Mundugumor), carved slit gongs, shields, masks, and various types of figure sculpture. Masks, like those of the Kambot, were usually hemispheric. Small figures used as flute stops had grossly enlarged heads that projected forward; they were often carved in conjunction with parrots and other creatures. Masks, as well as wood snakes used in sorcery and other such objects, often bristled with spike forms, which are a common motif in Biwat art. In relief carving, such as can be seen on shields, almost every line or band is serrated, creating a dazzling effect. The same technique was used in enormous paintings of crocodiles that were displayed at yam-harvest ceremonies.

The opposed-hook style of Sepik sculpture was predominant along the middle reaches of the Sepik River and among the hills ranging across the southern border of the Sepik valley, including the Hunstein Mountains. The most spectacular works in this style were figures carved by the Alamblak in the eastern Sepik Hills. The figures, known as yipwon, represent patron spirits of hunting and war. They are topped by a downcurved hook; directly beneath this is a human face, and below that is a vertical series of downcurved hooks. An oval element, representing the heart, appears next at about the centre of the figure; below the heart is a series of upturned hooks, and the whole is supported on a single leg. Small examples of these yipwon were personal amulets; larger figures, up to two metres high or more, were clan-owned property kept in ceremonial houses.

A second type of carving has also been recovered, usually from burial rock shelters of the Ewa, a now much-diminished group south of the Alamblak. These figures are related in general form to the yipwon, but their bodies are expressed as panels and scrolls rather than hooks. Other flat figures are of females in frontal positions with raised arms and hands.

The Bahinemo west of the Alamblak carved opposed-hook objects with no head or leg. They also made masks, for display only, which incorporated hooks and human features; these represented bush and water spirits. Groups farther west made hook carvings of the Bahinemo type and also carved hook patterns on shields and slit gongs. Other hook carvings are of uncertain provenance. They often have right-angled rather than curved hooks.

That the hook style was once predominant throughout much of the Sepik area is suggested by traces of it in still other styles. South of the river, masks of some Yuat, Keram, and middle Ramu rivers groups are framed in series of hooks. More remarkable, from far north of the Sepik, a number of the Abelam’s carvings incorporated opposed hooks in the form of bird beaks.

A number of small groups lived along the upper reaches of the Sepik River. The most productive were the Kwoma. Like the Abelam, they celebrated yam cults in ceremonial houses that were basically roofs supported on posts, without walls. The ridgepoles of the houses were carved with mythical characters, human and animal. The ceilings were covered with bark paintings with semiabstract designs recalling characters and incidents in myths; the finials on the gables were also carved with mythical figures and birds. Similar designs were used on pottery feast bowls and on daggers made from human bones.

The main nonarchitectural carvings—yena, human heads; mindja, long boardlike carvings with a head at one end; and nogwi, figures of women—were made for the three main rituals of the yam cult. The carving style is simple and massive, with heads having straight brows above a slightly concave facial place on which appear conical eyes, a long, heavy nose, and a small V-shaped mouth.