[Illustration: Inside the gorgeous gorges of the Big Bend of the Rio Grande, the river’s flow determines real time. Canoeists in fast water work the Eternal Now.] [Illustration: Other moods abound. Changing light conditions paint Santa Elena Canyon with subdued hues (opposite), then splash it with bold and saturated colors (following).] [Illustration: Santa Elena Canyon.] Human beings have lived in the Big Bend area for ten to twelve thousand years. The first to come were probably nomadic hunters following the big game that drifted south ahead of the last great continental ice sheet. They hunted elephant, camel, bison, pronghorn, and horses, as indicated by their kill sites discovered in the mesa and Pecos River country to the north and east of the park. But as the Earth warmed up and glaciers melted, a deadly dryness crept eastward from Mexico’s Sierra Madre Occidental and engulfed Big Bend. Moisture-loving plants died out or were driven out by drought-resistant species, and as the climate and vegetation changed, so did the animals. Many Ice Age mammals perished forever and the hunters themselves seem to have disappeared. Not surprisingly, the next people to infiltrate Big Bend were nomadic Indians adapted to desert life. Theirs was a follow-the-food economy, and they camped in caves and rock shelters close to such water sources as the Rio Grande and its tributaries, springs, and rock wells. They hunted desert animals for meat and skins, ate juniper berries, pricklypears, century plant hearts, yucca blossoms, and mesquite beans. They made baskets, nets, mats, and sandals from basketgrass and the long slim leaves of the yucca. Today, thousands of years later, remnants of these may still be found in dry caves. These prehistoric nomads also disappeared, perhaps killed or absorbed by the Jumanos, a semi-pueblo people who came to occupy the river valleys west of the park.