and 21,000 years ago, according to the U.S. Geological Survey. Previous estimates of human arrival into North American were 13-16,000 years ago. Paleo-Indians inhabited the shoreline of Lake Otero, a large lake that covered much of the Tularosa Basin. They used stone from the mountains to create projectile points, known as Folsom and Plano points, and attached them to spears for hunting mammoths, camels, ground sloths, and bison. Projectile points and stone tools have been found in the basin associated with ancient shorelines, streams, and hills. As the large ice sheet that capped the North American continent receded, Lake Otero began to evaporate, leaving behind Alkali Flat and Lake Lucero. The grassland died and the basin became increasingly arid, slowly changing into desert scrubland. The megafauna disappeared from the basin leaving behind fossil footprints. The Archaic people improved upon the hand thrown spear used by Paleo-Indians with the invention of the atlatl. After Lake Otero dried out, wind carried large quantities of gypsum sand up from the basin floor which accumulated into a large dunefield. Archaic people entered the Tularosa Basin about 4,000 years ago, after the dunes had stabilized, possibly attracted by a cereal grass called Indian ricegrass. The first evidence of agriculture is found in the Archaic period. Archaic peoples would tend to wild plants so they would produce in a more reliable manner and in larger quantities than they did naturally. Archaic people started living in small villages throughout the year to tend their fields. Hearth mounds are found within the dunes, which are the remains of prehistoric fires containing charcoal and ash. When gypsum is heated to it becomes a plaster that hardens when moisture is added and subsequently evaporates. The plaster cements these hearths in place, preserving them for thousands of years. The Jornada Mogollon people made pottery, lived in permanent houses, and farmed the Tularosa Basin. Evidence of their prehistoric presence dates back to about 200 CE. The Jornada Mogollon inhabited the basin until about 1350 CE when they moved away, leaving behind puddled adobe structures and pottery sherds. Over 700 years ago, bands of Apaches followed herds of bison from the Great Plains to the Tularosa Basin. The Apaches were nomadic hunters and gatherers who lived in temporary houses known as wickiups and teepees. The Apaches had established a sizable territory in southern New Mexico by the time European explorers arrived. They fiercely