According to Roosevelt, the Marajoara culture developed independently within the Amazon and featured both intensive subsistence agriculture and major public works. Roosevelt estimated that Marajó may have had a population of more than 100,000 people at its peak. The population lived in homes with tamped earth floors, organized themselves into matrilineal clans, and divided tasks by sex, age, and skill level. The arrival of Europeans in the sixteenth century was catastrophic to the indigenous population of the island; 90% died due to high mortality from Eurasian infectious diseases; they lacked immunity against these diseases that had become endemic in European and Asian cities. In contrast, however, during the 1918–1919 pandemic worldwide of the Spanish influenza, Marajó was the only major populated area not to have any documented cases of the illness. The island is also the location of the Roman Catholic Territorial Prelature of Marajó.