dated to 2800 BC). Starting around 3000 BC, evidence of large-scale exploitation of oysters appears. During the period 3000 BC to 1000 BC, shell rings, large shell middens that more or less surround open centers, were developed along the coast. These shell rings are numerous in South Carolina and Georgia, but are also found scattered around the Florida Peninsula and along the Gulf of Mexico coast as far west as the Pearl River. In some places, such as Horr's Island in Southwest Florida, resources were rich enough to support sizable mound-building communities year-round. Four shell or sand mounds on Horr's Island have been dated to between 2900 and 2300 BC. Timeline Early Archaic 8000 BC: The last glacial period ends, causing sea levels to rise and flood the Beringia land bridge, closing the primary migration route from Siberia. 8000 BC: Sufficient rain falls on the American Southwest to support many large mammal speciesmammoth, mastodon, and a bison speciesthat soon go extinct. 8000 BC: Hunters in the American Southwest use the atlatl. 7500 BC: Early basketry. 7560—7370 BC: Kennewick Man dies along the shore of the Columbia River in Washington State, leaving one of the most complete early Native American skeletons. 7000 BC: Northeastern peoples depend increasingly on deer, nuts, and wild grains as the climate warms. 7000 BC: Native Americans in Lahontan Basin, Nevada mummify their dead to give them honor and respect, evidencing deep concern about their treatment and condition. Middle Archaic 6500 BC–200 AD: The San Dieguito–Pinto tradition and Chihuahua tradition flourish in the Southwest. 6000 BC: Ancestors of Penutian-speaking peoples settle in the Northwestern Plateau. 6000 BC: Nomadic hunting bands roam Subarctic Alaska following herds of caribou and other game animals. 6000 BC: Aleuts begin to arrive in the Aleutian Islands. 5700 BC: Cataclysmic eruption of Mount Mazama in modern-day Oregon. 5500 BC–500 AD: Oshara tradition, a Southwestern Archaic tradition, arises in north-central New Mexico, the San Juan Basin, the Rio Grande Valley, southern Colorado, and southeastern Utah. Natives of the Northwestern Plateau begin to rely on salmon runs. 5000 BC: Early cultivation of food crops began in Mesoamerica. 5000 BC: Native Americans in the Pacific Northwest from Alaska to California develop a fishing economy, with salmon as a staple. 5000 BC: The Old Copper culture of the Great Lakes area hammers the metal into various tools and ornaments, such as knives, axes, awls, bracelets, rings, and