Final answer:
The traditional subject matter of Plains Indians' paintings changed primarily due to the eradication of bison and the transition to ledger art using paper, adapting after tribes were forced onto reservations.
Step-by-step explanation:
The transformation in the traditional subject matter of Plains Indians' paintings can be attributed to several significant changes in their way of life and available resources.
The eradication of bison herds by the U.S. government, forcing tribes to adapt to new materials like paper and fabric for their art, is one primary reason. Notably, ledger art began when ledger books and other materials were left behind by traders and military personnel passing through the region.
Additionally, the forced relocation of many tribes onto reservations introduced drastic changes in the content of their artwork. Artists began to include scenes of life before the marches to reservations, preserving their tribal histories on ledger paper as opposed to bison skins.
The art evolved further as Indigenous artists, emerging from colonial influences post-World War II, began experimenting with modern theories and incorporating traditional themes into contemporary works.
This changing narrative is also reflected in how traditional Native American art became commoditized, with non-Native collectors often influencing the narrative, which led to a shift in the art's purpose and representation.
Today, there is a resurgence of Native American artists who intertwine their cultural heritage with modern artistic styles, creating a dynamic and evolving art expression that honours their past while navigating contemporary challenges.