by Brian Fagan
Marine productivity in the Santa Barbara Channel rose and fell with cold and warm intervals. During cool periods, the foraminifera show that there was only a slight temperature gradient between 197 feet (60 meters) and the surface, as if the natural upwelling in the channel was very strong and there was constant vertical mixing of seawater. This process was especially intense between 1,000 and 500 years ago. Upwelling, and marine productivity, were dramatically reduced during the warmer cycle between 2,900 and 1,500 years ago. Furthermore, ocean temperatures displayed marked instability between 1,500 and 800 years ago.
The climatic shifts in the Santa Barbara Channel are matched by those recorded on land. Especially low sea surface temperatures appear to coincide with the prolonged drought cycles over much of western North America, especially with those recorded from bristlecone pine tree rings in the White Mountains of eastern California.
The Santa Barbara Channel was home to many Chumash Indian groups, whose ancestry goes back deep into the remote past. When the first European explorers anchored off this coast in the sixteenth century, they reported large villages and dense populations both on the Channel Islands close offshore and on the mainland.10 For many centuries, we know, the coastal population remained relatively sparse. Then, after about three thousand years ago, trading activity between neighboring communities and between the coast, the offshore islands, and the interior picked up rapidly. Judging from the number of archaeological sites on the Pacific coast, the population increased as fishing intensified. Population densities increased even more after about thirteen hundred years ago, as maritime productivity increased with active upwelling.
The changes are particularly noticeable on the Channel Islands, where food resources were patchy but shellfish and inshore fisheries abounded. After about A.D. 450, sea temperatures cooled for some ten centuries, resulting in strong upwelling and an abundance of fish of all kinds. This was a period when coastal populations exploded and permanent settlements along the Pacific became more commonplace. On the Channel Islands, the major settlements developed more or less equidistant from one another, as if they had distinct, well-marked fishing and foraging territories. Many of these settlements continued in use into historic times, so their inhabitants appear in mission records and in oral traditions recorded in the late nineteenth and early twentieth centuries. We know this because on November 20, 1884, Juan Estevan Pico, a Chumash speaker who lived in the San Buenaventura Indian community at the southern end of the Santa Barbara Channel, compiled a list of no fewer than twenty-one island villages.11 The names of at least eleven chiefs appear in baptismal records, most of which date to between 1814 and 1822. The rapid depopulation of the islands resulted from the effects of European diseases, the collapse of cross-channel trading, and an extended drought.
On Santa Cruz Island, the largest of the archipelago, most of the larger settlements lay in sheltered bays, where the inhabitants could either command a good view of the coastline or could see nearby villages placed on strategic headlands that served as lookout posts.12 Each settlement occupied a strategic position close to reliable sources of drinking water. As time went on, territorial boundaries seem to have become more rigid and were often marked by cemeteries. For example, most cemeteries on nearby Santa Rosa Island are associated with major villages, both on the coast and in the interior, some of them perhaps serving as territorial markers.
As populations increased and the islands became more crowded, so fighting escalated. The surge in violence came at a time when signs of dietary stress become more commonplace on the bones of the dead. The biological anthropologists Patricia Lambert and Phillip Walker have chronicled numerous examples of forearm fractures sustained when parrying blows, nasal fractures, healed skull wounds, and injuries caused by spears or arrows.13 Many of the head injuries healed, having been inflicted by relatively slender blunt instruments.
Both the malnutrition and the increased violence took hold at a time of great climatic instability and marked social change. Santa Barbara Channel waters were generally cool and productive, but on land conditions were generally dry, with serious droughts well recorded in tree rings and deep-sea cores in about 950 and 1250. The droughts resulted in a consolidation of smaller settlements into larger ones, and in the actual abandonment of areas with marginal water supplies around the islands as well as on the mainland.
Violence and increased competition for food were insidious consequences of major drought cycles. On the islands, every settlement was matrilocal—that is, the women stayed in the villages of their birth, while the men married into them. This had a strategic advantage, in that it fostered alliances between neighboring villages where blood-related males dwelled. At the time of the great droughts, we know from linguistic research concerning historic populations that islanders and mainlanders spoke different languages, as if there were two distinct groups. The institution of matrilocal residence may have developed in the face of repeated threats of attack from the mainland, where food supplies were short and territories crowded.
As island populations increased, so the pressure on highly regarded foods like red abalone increased. These meaty shellfish flourish in shallow water and can reach a considerable size. Small groups of women would wade in tidal pools, diving in shallow water to pry abalone off the rocks. They would toss their catch into shallow baskets, swimming across the rocky bottom just below the low-tide level, timing their visits for the lowest tides of the month. Back at camp, they would deftly pry open the abalone with bone levers, and then pound the delicate flesh before roasting it. By the time of the warm centuries, the abalone taken were much smaller, but the food shortfall was overcome by widening the diet to include many more fish species over and above the inshore kelpbed species favored in earlier times. Just like Great Basin foragers, the Chumash learned the advantages of a broad diet. By 1100, the fishers were venturing into deeper water aboard the sewn-plank canoes known as tomols, taking deep-water species such as shark and tuna with hook and line. They were also using sophisticated toggle harpoons against sea mammals, a technology long in use in the far north. This intensified fishing was a deliberate effort to widen the diet during a harsh drought cycle.
The Channel Islands have relatively few edible plants, and they lack the plentiful acorns so important on the mainland. For centuries, the islanders imported acorns by exchanging them for thousands of shell beads manufactured with fine drills made with the good quality chert found on Santa Cruz Island.14 At a few island sites, the remains of plants only native to the mainland provide clear evidence of this trade after 1200. Interestingly, the shell bead trade accelerated dramatically during the late first millennium, just at the time when droughts deepened and competition for plant foods intensified. At the same time, the people relied heavily on fish, moving into more permanent villages as they became tethered to local fishing grounds and beaches where they could land and maintain their canoes.
Political and social circumstances on the islands were volatile during the drought centuries. As the population grew at a time of bountiful fisheries, so competition for the best fishing spots and the richest shell beds would have intensified. As we have seen, violence broke out, people were killed, territorial boundaries hardened and were defended more aggressively. Inevitably, too, some individuals or kin groups acquired control of specific fishing areas or desirable plant patches. Such power gave them enhanced authority, and, perhaps, a higher position in new social hierarchies that developed over the generations. Local society became more hierarchical, ruled by local chiefs who formed alliances with one another and sometimes presided over several villages. Some of them were also canoe captains, a specialty so valued that in later times they were members of a formal brotherhood.
On the islands, people responded to drought by living in densely inhabited villages. Their leaders controlled a rapidly growing trade with the mainland that seems to have resulted in a sharp decrease in violence. People suffered from malnutrition on many occasions, but the suffering ma
y have been less than that on the mainland, where drought in the interior decimated acorn crops and drastically reduced stands of wild plant foods. On the mainland, as on the islands, each community adopted the classic response to severe drought: they placed their settlements close to permanent water sources. Judging from the results of crowding in shantytowns on the edge of modern industrial cities, we can speculate that there were serious problems with water pollution and sanitation in now much more crowded settlements, with the inevitable epidemics of dysentery and other diseases that were less common in small villages In the end, it seems that the island and mainland chiefs developed social mechanisms for damping down the competition and violence that resulted from food shortages. Around 1300, we find complex alliances and other mechanisms for reducing strife coming into play, and these were closely connected with an explosion in island–mainland trade and in exchange with groups living far away in the interior, even as far away as the Southwest. These mechanisms endured long after the great droughts of the warm centuries were forgotten, in a region where unpredictable rainfall and changing sea temperatures made everyone vulnerable to climate change, and where the experience of earlier generations provided precedent for people anchored to coastal fishing grounds or to acorn harvests.
The Chumash maintained contacts not only with neighboring groups, but also with people far inland. Their trade networks extended as far as the Southwest, where Ancestral Pueblo farmers responded to the same catastrophic droughts with different strategies.
A HOT, SULTRY afternoon has settled on the floor of Chaco Canyon, New Mexico. The air is heavy and still, weighing on the visitors passing through the empty rooms of Pueblo Bonito. A huge bank of black thunderclouds masses on the western horizon, mocking the bright sunlight shining on the canyon walls. The clouds pile ever higher. Distant lightning flickers through the menacing overcast; thunder rumbles ominously. Violent wind gusts sweep through the canyon; a few heavy raindrops spatter the sandy path. The visitors run for shelter under a nearby overhang. A wall of gray approaches, but evaporates as the approaching storm changes course and drops its load downstream. Bright sunlight returns to bake the canyon floor once again.
If you live in a semiarid environment, you have to be prepared to roll with the climatic punches. The Ancestral Pueblo of the Southwest were masters of flexible and opportunistic living in landscapes where movement meant survival. A modern-day Tewa Indian oral tradition from the Southwest proclaims: “Movement, clouds, wind and rain are one. Movement must be emulated by the people.”15 Great Basin bands survived through mobility. Coastal fishing groups moved into more densely populated villages. All of these people were hunters and wild plant gatherers, but others cultivated maize and beans and lived by farming the land. Farming was not a viable option in desert areas; California Indians with their acorn harvests had no incentive to grow crops. But, in the Southwest, conservative farmers, who were experts at water management, thrived in often agriculturally marginal environments for over three thousand years.
Chaco Canyon lies in the heart of the San Juan basin, a seemingly empty landscape that appears to stretch forever.16 Water in any form is short in the basin; summer rainfall arrives as thunderstorms, gentler, if sporadic, winter rains in the form of snow between December and March. But the amount of rainfall is very small, invariably localized, and utterly unpredictable. Short-term climatic shifts such as El Niños or prolonged droughts like those of the Medieval Warm Period could have a profound effect on agriculture on a year-by-year basis. Chaco Canyon is about 18.6 miles (30 kilometers) long and between a third and nearly a mile wide (0.5 and 1.5 kilometers). After storms, the Chaco Wash flows strongly through the canyon, which is also watered by side streams and by natural seeps at the foot of the surrounding cliffs. But in times of drought the canyon floor is bone dry.
Hardly a promising location for any form of agriculture, one would think, but between the ninth and twelfth centuries, at least 2,200 people dwelled within the canyon, and its population swelled considerably at times of major ceremonies. Numerous small hamlets of a few stone houses thrived at Chaco, also nine large pueblos, commonly known as great houses. The permanent residents of Chaco farmed fertile patches of soil with the simplest of digging sticks and hoes. How many of them lived in the great houses rather than in hamlets we don’t know, but places like Pueblo Bonito were capable of housing hundreds of people—provided the visitors brought their own food. The carrying capacity of the canyon itself was minuscule relative to the size of the great houses. On the south side of the canyon, the farmers relied on rainfall, while on the north, they cultivated maize and beans in densely packed, gridded fields.17 By using canals about 4 feet (1.2 meters) wide, they channeled water stored in earthen dams through simple masonry gates from one gridded field to another. The farmers increased agricultural production dramatically as a result, but at a cost of increased vulnerability to severe drought, for their agricultural systems became less diversified. Fine-tuning water control systems on this small a scale would only work if there were enough rainfall to fill the canals and irrigate the field grids. In most years, there was not. The solution was diversification, with each household farming a variety of microenvironments, spreading the risk as one would when investing in mutual funds. But they never produced enough to feed everyone who visited the canyon.
The expansion of Chaco’s great houses between 1050 and 1100 depended in large part on a highly vulnerable agricultural system that worked fine in good rainfall cycles, but was disastrous when the rains failed. But, despite this built-in vulnerability, the Chacoans built a series of great houses that were architecture on a grand scale, far larger than anything needed by a mere 2,200 people. Most of the Chaco pueblos were semicircular, often with several stories and numerous rooms associated with large and small kivas, subterranean chambers used for rituals of all kinds. The great houses are so unexpected and spectacular that some people call Chaco the Stonehenge of America.
No one knows why such imposing great houses rose in this remote, arid canyon, but there is universal agreement that Chaco became a place of supreme ritual importance between the ninth and twelfth centuries. People traveled here from far away, bringing grain, timber beams, turquoise for ornaments, and exotic commodities such as tropical bird feathers, presumably at times of major ceremonies such as those that marked the passage of the solstices. The most imposing of the great houses, Pueblo Bonito, was begun in about A.D. 860 and enjoyed a complex architectural history that lasted until about 1115. By this time, Chaco exercised a profound cultural and spiritual influence over an enormous area of the San Juan basin. A series of symbolic and irregular “roads” radiated from the canyon, but their function and symbolic significance eludes us.18
Experts have debated the significance of Chaco for generations. Perhaps the most powerful individuals in the canyon were religious leaders. They were guardians of the spiritual knowledge that governed a society where religion and agriculture went hand in hand. By combining agriculture and clever water management with complex ritual beliefs, the people flourished in times when rainfall was relatively abundant. Here, human existence depended not only on water management, but, they believed, on the meticulous performance of elaborate rituals and dances, on the skill of people who were guardians of sacred knowledge. This was why such stupendous great houses rose in an arid canyon, where the setting was spectacular. People came from many miles away, drawn by the powerful spiritual associations of the place.
Chaco had developed rapidly during a long period of relatively plentiful rainfall by San Juan standards. Tree rings tell us that the persistent and increasingly severe droughts that affected so much of the American West descended on the canyon after 1100, at a time when Chaco’s need for timber and building labor was at its height. Agricultural productivity withered; water supplies slowly evaporated. To the people who lived stoically through the drought, it must have seemed as if the forces of the supernatural had deserted them, that their leaders had lost their ability
to communicate with the gods. Within a half century, the great houses were deserted. The Chacoans had moved elsewhere.
Chaco Canyon July–August
Precipitation Reconstructed from Chaco Canyon National Monument and Bloomfield
A plot of rainfall in July–August at Chaco Canyon, New Mexico, A.D.600–1300. Reconstructed from tree-ring sequences from the canyon using Bloomfield’s method for analyzing time series. The statistically derived dark line shows general trends, while the spiky lines denote exceptional rainfall years. The drought of the 1140s and the thirteenth-century great drought can be clearly discerned.
THIS PATTERN OF movement was a familiar strategy in an area where rainfall ebbed and flowed and no single community was completely self-sufficient. No one at Chaco, or elsewhere in the Southwest, had any illusions about crop failure and hunger. Every family maintained kin ties with communities elsewhere, traded with them, responded with food when need be. By the same token, people living in better-watered areas knew that their kin would move to live among them if conditions for farming were better than at home. Chaco itself exercised an influence over a wide area, especially to the north and west, where people moved after 1100. Other pueblos rose to prominence, among them Aztec above the Animas River; then, even farther north, great communities flourished in the Moctezuma Valley and in Mesa Verde, places where densely populated settlements lay close to more dependable water supplies.19 But, once again, a severe drought from 1276 to 1299 caused people in these great pueblos to disperse to escape conflict as more people crowded into great houses and food supplies grew increasingly scarce. High infant mortality rates and reduced birthrates owing to health problems may have caused local population densities to fall, but also the social and technological means to deal with the crisis were inadequate. So the people relied on their ancient strategy of movement, going to live in better-watered areas to the east, south, and west, where there were already communities with friendly kin capable of supporting large numbers of people.
