Working in the 1950s in some of her earliest research, American Betty Meggers suggested that the society migrated from the Andes and settled on the island.

In the 1980s, another American archeologist, Anna Curtenius Roosevelt, led excavations and geophysical surveys of the mound Teso dos Bichos.

[1] The Native Americans of the Amazon rain forest may have used their method of developing and working in terra preta to make the land suitable for the large-scale agriculture needed to support large populations and complex social formations such as chiefdoms.

[1] Conclusive proof of this ancient human presence in the Amazon is the Pedra Pintada cave, located near the city of Monte Alegre, in Pará (Brazil), which was studied by the American archaeologist Anna Roosvelt.

[5] Rossetti et al. proposed that the archaeological settlements associated with isolated or compound mounds were "systematically developed on top of extensive elevated surfaces formed due to natural sedimentary processes".

Trees such as the açai and tucuma palms also provided important supplements in the Marajo diet, as well being used for manufacturing items such as baskets or canoes (Roosevelt 1991; Meggers 1957).

This method of mass harvesting is not as useful in the rainy season as it is during the dry months when fish are trapped in receding streams or ponds (Roosevelt 1991: 382-383).

Pre-historic peoples of Marajo Island may have also constructed ramps, canals, ponds, and drained fields found near earthworks mounds, but most of the evidence has likely been buried by sediment in seasonal floods (Roosevelt 1991: 33).

Evidence for trade networks at Marajo is found mostly in lithics, because the island has no local source of suitable igneous or metamorphic rock (Roosevelt 1991: 9, 348; Meggers 1957: 371).

There are also monumental earthworks, causeways, ramps, canals, ponds, and drained fields that have been buried by extensive sedimentation (Roosevelt 1991: 33, 331-333, 422) Travelers in the 1800s noted both the presence of mounds and the beauty of the ceramics found inside them or exposed on their sides.

Buried in house floors constructed on the tops of the mounds, the elaborately decorated urns contain the remains of significant individuals.

[10] The people on Marajo produced many diverse artifacts (Roosevelt 1991: 59-60) such as pottery vessels (urns, jars, bottles, cups, bowls, plates, dishes), figurines, large statues, pubic covers, pendants, ear and lip jewelry, whistles, spindle whorls, and ceramic miniatures of axes, mashers, hammers, and other tools.

Elaborate pottery vessels were found in garbage fills between houses and in graves, but not around hearths, which contained only plain domestic wares (Roosevelt 1991: 37, 402).

The general pattern of change found throughout artifacts on Marajo, especially in ceramics, is one that moves toward more complex, elaborate, and specialized wares through the Marajoara Phase.

Although some characteristics do point to stratification, the evidence regarding inequality and leadership is inconclusive as to whether it was gender or class based, or whether it represented centralized rule (Roosevelt 1991: 411).

Ethnohistoric records describe civic-ceremonial leaders, but the Marajoara existed several centuries prior to European contact and may have been quite different from the later contact-period societies.

A more comprehensive, systematic investigation of burials and houses is required to tell whether the differentiation in food production and consumption was based on class or gender (Roosevelt 1991: 403, 417).

The fact that women are largely absent from elaborate burial urns and number very few at all compared to male skeletons could be regarded as evidence for gender stratification.

Marajoara iconography and art portrays women with shamanistic powers and roles (Roosevelt 1991: 410), consistent with societies that reckon descent through a mythical female ancestor.

There were parallels to Amazonian cosmology, which understands the universe to be gender divided, with men related to the sun and women to the moon.

While skeletal remains have not been analyzed for trauma patterns yet, they do show peculiar signs of muscle development that strongly suggest regular participation in warfare (Roosevelt 1991: 406-407).

Other than the defensive position of residences atop earthen mounds, there is relatively little evidence that can either confirm or deny the existence of warfare or localized violence.

Buried in house floors constructed on the tops of the mounds, the elaborately decorated urns contain the remains of significant individuals.