Over 12,000 years ago, Idaho's first people survived by following herds of big game, and about 7,000 years ago Native Americans in this area followed the earth's natural cycles by camping together for protection in the winter and breaking into small family bands to forage in the summer. This pattern began changing in the early 18th century, when local tribes obtained their first horses from other tribes, bringing new wealth and power, increasing interaction with other tribes, and allowing hunting and gathering over a wider area. In the 1830's, local tribes, including the Shoshone, Paiute, and Bannock, began trading with Euro-American fur trappers and missionaries passing through southern Idaho, and peaceful exchanges beneficial to both groups increased in 1842 when wagon trains crossed southern Idaho on the Oregon Trail. As they moved through the Boise Valley, the trains obtained food, stock, and services from native bands in exchange for a variety of goods and animals. What was only a few hundred wagons in 1842 became a flood of 8,000 emigrants in 1853, and for every emigrant there were nearly four head of stock overgrazing the land along the trail. Trees and sagebrush disappeared in the smoke of cook fires and accidental wildfire, and a curtain of dust could be seen for miles. As resources stretched thin, contact between the two cultures began to be strained. Insult, injury, and criminal acts resulted in retaliation, often against innocents. The nearby Hudson's Bay Fort Boise was lost in the 1853 flood and was replaced by only a temporary structure. Local bands blamed emigrants for an increase in disease and poisonings and a loss of game. By 1854, southern Idaho had become a dangerous place with little protection for both wagon trains and native bands. Toward the end of the 1854 migration, the hostility boiled over into violence, and a local band, the Winnasc, began outright attacks on isolated trains. Mounted on horses and armed with rifles, they proved a deadly threat to the last few emigrants hurrying toward Oregon.