Final answer:
In the second half of the 19th century, an important change in the indigenous way of life was the transition from agriculture to a nomadic lifestyle, significnatly influenced by the reintroduction of the horse. The Mississippian culture also experienced a shift due to the adoption of maize agriculture, impacting their social structure and settlement practices.
Step-by-step explanation:
An element of change in the indigenous way of life in the second half of the 19th century was the transition from agricultural practices to a nomadic lifestyle. This shift, particularly among the Plains groups, was partially due to the reintroduction of the horse to North America, which facilitated greater mobility and an efficient means for hunting bison. Additionally, a major cultural shift in the Mississippian tradition was the adoption of maize agriculture, which had a profound effect on social organization and settlement patterns.
The 19th century also saw various threats to the viability of nomadic societies, such as climate change, industrialization, and the imposition of national borders. Despite these challenges, not all groups adopted an agrarian lifestyle; some, like the Indigenous peoples of Australia, continued their hunter-gatherer ways, which they deemed more suitable to their needs and environment. The fact that these changes coincided with colonization and industrialization, which provided some tools but also exerted pressure, underlines the complexity of change during this period.