Jungle
Page 14
Chapter 7
FARMED FORESTS
Following their arrival across a number of the world’s environments during the late Pleistocene, humans began to make increasingly intensive interventions into the natural world in order to feed their growing populations and complex social networks. Using fire to shape the types of habitats in their surroundings, moving particularly nutritious plants, and carrying animals beyond their wild ranges as handy protein packages, human populations began to reconfigure the distribution of particular species and even entire ecosystems. During the terminal Pleistocene and Holocene transition (c. 12,000 to 8,000 years ago), and perhaps also before, these interventions became even more intrusive. Human selection for docile, social animals or carbohydrate-rich, clustered plants eventually led to morphological and genetic changes in certain species that became formally “domesticated” as part of what has been called the “origins of agriculture.” Western perceptions of what this “agriculture” should look like—namely, expansive fields of cereals like wheat or barley and dense, ranging herds of cattle, sheep, and goats—have meant that much archeological, archeobotanical (the study of plants preserved in archeological sites), and zooarcheological (the study of animals preserved in archeological sites) research into its origins has centered on the dry river valleys of the “Fertile Crescent” in the Middle East, where our familiar domesticates emerged before spreading across Europe during the Neolithic (c. 9,000 to 4,000 years ago).1
Tropical forests have, by contrast, frequently fallen by the wayside of such discussions. How could the dense green tangle and poor acidic soils of these environments provide our daily bread, our “usual” at the pub, or our regular pints of milk or blocks of cheese—let alone preserve traces of plants and animals we might use to retrace the footsteps of the first farmers? Surely these forests have to be avoided or removed for such activities to be successful? But here is the problem. We are so stuck in our Euro-American worldviews of what “agriculture” should be—a settled economy, fully reliant on domesticated plants and animals, extensive land clearance, and monotonous field systems—that we miss other, equally ingenious, and equally impactful roads to “food production.” If we instead focus on the farming practices that lead to domestication, we open ourselves up to a whole new series of possibilities. Taking this approach, we can look at cultivation as human behaviors that promote the survival, reproduction, and growth of certain plants and at herding as human behaviors that shape the mobility, population, and anatomy of certain animals to provide a wider lens for viewing how our species began to insert itself into the natural world. Instead of relying on a narrow, confining definition of “agriculture,” by looking at the experience and process of farming or “food production,” we can gain a truly global perspective on one of the most pivotal periods in human history—one that, of course, can include some of the most biodiverse environments on the planet: tropical forests.2
Far from being unproductive sideshows, tropical forests display some of the earliest human manipulations of plants and animals in the name of food security as early as 45,000 years ago. These diverse habitats include montane or seasonally dry forests with penetrating light and fertile soils, where burning can be easily practiced, as well as wet rainforests. And they potentially hosted some of the earliest examples of deliberate cultivation across the terminal Pleistocene–Holocene boundary, as humans changed landscapes and planted trees with sugar-rich fruits and tubers in places they would not normally grow. We will see how archeobotanists and zooarcheologists have shown that some of the most used domesticates around the world today, produced by these cultivating and herding behaviors, actually have their origins in tropical forests. In fact, a significant portion of your weekly shopping lists comes from tropical forests without you even realizing. Eggs, cornflakes, tortillas, sugar lumps, chocolate bars, ham and pineapple pizza, pepper, cigarettes, and the food spreads or cosmetics that contain palm oil are just some of the diverse products that owe their existence to the “jungle.” In some cases, tropical farming practices did take the form of “agriculture,” with novel field systems leading to prehistoric deforestation and major ecological changes that provide a stark warning to us today. But in others, domesticated resources were slotted into existing, sustainable hunting, gathering, and fishing economies. Whereas we once considered tropical forests to be environments where “farming” was doomed to failure, we now know that over the last 10,000 years, human societies have modified tropical forest plants, animals, and entire landscapes the world over to provide many of the supermarket items we all take for granted today.3
TROPICAL FORESTS HAVE a reputation for having been some of the most “pristine” environments prior to industrialization. However, they actually have one of the longest records, if not the longest, of human modification. As early as 45,000 years ago, with the arrival of our species in the tropics and subtropics of Southeast Asia, Near Oceania, and Australia, humans were burning tropical forest ecosystems to promote grassland patches and open up forest floors. This enabled them to pick and choose a cornucopia of resources from a variety of open areas, drier forests, and denser rainforest. Some groups were even managing plants by moving them. Starchy plants, like yams, were potentially carried across the Wallace Line as early as 40,000 years ago. Meanwhile the range of plants like the sago palm, various yams, and taros across mainland and island Southeast Asia, and perhaps even Australia, by the start of the Holocene certainly has the ring of human handiwork about it. Even tropical animals were not left in peace by our early ancestors. In Near Oceania, by 20,000 years ago, seafaring people carried furry bandicoots and cuscuses (not to be mistaken for couscous!) as snacks—moving them beyond their natural homes and onto more isolated islands, such as those of the Bismarck Archipelago, where they were to thrive. Why, then, have archeologists and the public alike so often ignored tropical forests as possible crucial locations where Homo sapiens performed early food-production experiments? It certainly hasn’t helped that many productive tropical plants are soft and fleshy, not prone to preservation over long periods, while bones often face the harsh acidity of the soil upon burial. Unlike more temperate or arid areas, where charred seeds or ample animal remains allow the observation of gradual changes from wild to domesticated features, similar detective work in the tropics has therefore certainly been at something of a disadvantage.4
Nevertheless, archeologists are stubborn and used to working with what they have. Archeobotanists and geoarcheologists, like Professor Tim Denham of Australian National University, have turned to their microscopes to try and identify uniquely shaped starch grains or characteristic microscopic silica structures (phytoliths) left behind by particular plants in tropical soils. While the work is difficult and prone to contamination from modern foods eaten in and around the laboratory or excavation sites, these painstaking methods can revolutionize our understanding of food production in more challenging environmental contexts. In fact, using these approaches, Tim and his colleagues think that they have found a key, early heartland of independent plant cultivation and domestication in tropical forests. This heartland not only challenges the time line of global food production but also causes us to face our own biases and assumptions as to what “agriculture” looks like—located, as it is, in the middle of a wet, sticky swamp. As Tim says, “At Kuk Swamp, in the Wahgi Valley of highland Papua New Guinea, archeological excavations from the 1970s and 1990s have allowed us to reveal one of the earliest farming landscapes found anywhere in the tropics.” Marking out and excavating two hundred trenches, archeologists have uncovered a series of “phases,” from between 10,000 and 4,000 years ago, that document the increasing lengths humans went to in order to modify the landscape to make it better for the cultivation of some of the world’s modern tropical favorites: taro, banana, and even sugarcane. In fact, this evidence makes Kuk Swamp one of the earliest sites where farming practices by Homo sapiens have been observed—not in temperate or dry river valleys or grasslands but in highland,
humid, tropical forest wetlands around 1,500 meters above sea level.5
Phase 1 of Kuk Swamp, dated to approximately 10,000 years ago, has been famous since archeologist Jack Golson identified a series of drainage ditches. Back in the 1970s and 1980s, Jack put the cat among the archeological pigeons by suggesting that these ditches were a deliberate attempt by humans to drain the local wetland and help the growth of carbohydrate-rich plants like taro and banana. This early evidence has proven controversial, with a lack of direct verification of plant cultivation, suggestions that the ditches may, in fact, be natural, and an absence of similar landscape modification anywhere else in New Guinea raising some reservations. Nonetheless, banana phytoliths were found in this phase, in a more open environment than they would usually appear, hinting that some human gardening was in progress. Not just that, but a number of environmental records from the terminal Pleistocene and early Holocene have shown an increased incidence of human burning 10,000 years ago and the opening of forest across montane New Guinea, including directly around Kuk Swamp, conveniently providing the perfect environmental storm of forest patches for bananas, open forest floors for taros and yams, and grasslands for sugarcane. Some permanent settlements have also been identified in the region, suggesting growing populations and humans investing more in particular parts of the landscape, perhaps linked to the initial cultivation of these few key, managed crops, though Tim remains skeptical about these. The jury also remains out on this earliest phase of food production at Kuk Swamp. If proven, however, it would be some of the first deliberate food production and cultivation found anywhere in the world.6
Modern genetic evidence has certainly shown that an independent domestication of taro, the greater yam, and bananas occurred in Near Oceania before expanding out around the world. Today, the Eumusa banana found in the region is one of the most used domesticated bananas globally. Tim and his team of “microbotanists” (named for the diminutive size of the plant parts they are working with) have provided clear evidence by Phase 2 (c. 7,000 to 6,400 years ago) and Phase 3 (c. 4,400 to 4,000 years ago) of the presence of starch grains and phytoliths of taros, bananas, yams, and precursors of sugarcane, planted in direct association with clear, planned, and extensive drains and ditches dug by the local human population, during a time when people also started transitioning to a more sedentary lifestyle. The well-thought-out maintenance of plants that liked forests and plants that liked more open grasslands would have provided a set of important food stores for growing human populations facing fluctuating climates in the cool highlands at the terminal Pleistocene–Holocene transition. It will always be challenging to try and identify exactly when these plants became “domesticated” based on these tiny traces, but archeologists around the world increasingly accept that the early Holocene plant-management strategies at Kuk Swamp show a step change in human influence on plant life cycles and growing conditions—a new relationship with some of the plants many of us regularly have in our kitchens or put in our tea today. Kuk Swamp’s importance to world archeology was, in 2008, confirmed by the granting of UNESCO World Heritage Site status for the entirety of the site’s remarkable 116-hectare span, making it a true giant of prehistoric farming.7
Figure 7.1. Present-day mound gardening of sweet potato in New Guinea. Robin Hide, Tim Denham
Kuk Swamp is significant not just because it calls into question all of our assumptions about the timing and location of “agricultural” origins but because it also challenges our assumption about what the earliest farming societies looked like. The cultivation of bananas, tubers, and sugarcane at Kuk was not the rapid product of a single “inventor” or “inventors.” Instead, it was the end point of a long process begun by the first humans in Near Oceania who burned forests to maintain profitable mixtures of resources. Certainly, this reached new levels at Kuk, but it did not happen overnight and had a long, tropical trajectory. Furthermore, the development of cultivation at Kuk did not lead to sweeping changes. Not everyone instantly took to cultivation, and only later in the Holocene did it become a permanent fixture of New Guinea economies. With a team of researchers, I have worked at the site of Kiowa, in the same environments and at the same altitude as Kuk Swamp, to show that human populations just over one hundred kilometers away continued to hunt possums, cuscuses, and tree kangaroos between 12,000 and 500 years ago, even as groups at Kuk were developing and intensifying “food production.” Evidently, then, not everyone saw the increasing tending of specific plants as the revolutionary, world-shattering idea we imagine it to be today. Looking on at the new experiments being undertaken at Kuk, some people, in one of the next valleys over, were more than happy to continue to shape forest environments more broadly through burning, to gather nuts, and to hunt forest prey in a manner that, as we saw in Chapter 6, had enabled them to gain their first footholds in this tropical region. We often assume that farming was an inevitability, something humans grappled to attain once discovered. Here, in tropical New Guinea, however, it was just one more way of managing landscapes that had reliably provided for humans for thousands of years.8
FROM THE EARLY Holocene (11,700 to 8,200 years ago) onward, a number of different societies began to perform farming practices in tropical forests. These interventions were to result in some of the planet’s key dietary “staples.” Today, maize, or “corn,” is the most produced grain in the world, and it has long provided the basis for many of the increasingly dense and complex societies that appeared across the Americas during the Holocene. Although it is often portrayed as an ideal arid-adapted crop, one that might sustain us to the brink of drought-filled doomsday scenarios, microbotanists, like Professor Dolores Piperno of the Smithsonian Tropical Research Institute and Smithsonian National Museum of Natural History, have shown that its origins actually lie in the warm, wet seasonal tropical forest habitats of Mexico. Traditionally, maize domestication has been dated to 6,000 years ago based on charred cobs found in ideal preservation conditions in the semiarid highlands of Oaxaca alongside squash, gourds, and beans. “However, these cobs almost certainly do not represent the first cultivation of maize, and similar remains are simply not preserved in the wetter areas its wild ancestor is known to inhabit,” Dolores tells me. Instead, applying the same microbotanical approaches that were performed at Kuk Swamp, Dolores and her team discovered earlier evidence for maize cultivation 9,000 years ago in the tropical, humid Balsas River valley, in agreement with recent modern genetic evidence for the timing and geographical range of maize domestication. Maize is not, however, the only important modern domesticate the tropical forests of the Americas had to offer.9
The stifling conditions of the wet tropical rainforests of the Amazon Basin were once thought to have made any type of farming activity absolutely impossible prior to colonial and industrial clearance. Indeed, past human impacts on the Amazon rainforest have generally been thought to have been minimal. Nevertheless, starch, phytolith, and genetic research has now shown that the significant root crop manioc, or cassava, was first cultivated and domesticated there, in a process that began as early as 10,000 years ago. Falling just shy of the potato, a domesticate that itself emerged in the montane tropical environments of the Andes, manioc is today the second-most important root crop globally, feeding growing populations across Latin America, Africa, and Asia. The importance of the Amazon for prehistoric food production does not stop there, however, as it was also the site of the domestication of pineapples, avocadoes, and peanuts during the middle to late Holocene. Chili peppers were also most likely domesticated just south of the Amazon Basin in drier tropical forest and woodland habitats. Meanwhile, cacao was probably domesticated, or at least semidomesticated, in the Amazon Basin (although the Central American tropics have also been suggested as the geographical origins for this key ingredient of the chocolate that many of us cannot do without today).10
Sweet potato, an increasingly popular food in trendy restaurants across Europe and North America, was also cultivated in the American tropics, so
mewhere between Colombia and Venezuela in the south and Mexico in the north. Although poor preservation of yet another squishy but rich tuber has made tracking down its origins challenging, starch grains of sweet potato, from residues of tools interpreted as having been used for plant processing, have now been dated to 7,700 years ago in the montane tropical forests of Colombia, and firm data exists for domesticated sweet potato 4,500 years ago in Peru. By 1,000 to 500 years ago, this root crop was also being cultivated not just across Latin America but throughout the Pacific among the precolonial societies of the Cook Islands, Rapa Nui (Easter Island), and Aotearoa (New Zealand). It is also worth noting that prehistoric societies across the tropics of the Americas also manipulated many wild, semidomesticated, or domesticated trees. The modern genetics and distribution of the hulking Amazon nut (Brazil nut) tree, for example, has been shown to map closely onto ancient archeological settlements, suggesting that humans carried and planted protein-rich Amazon nuts in a form of sophisticated agroforestry. Peach palm was also domesticated somewhere in the Amazon Basin. Finally, beyond foods, per se, the Neotropics have also produced some more “recreational” crops. The Madeira River valley in the southwestern Amazon Basin was the origin of one of the major sources of modern crime across Latin America and, indeed, globally: coca (the constituent of cocaine). It also witnessed the domestication of the tobacco plant that fills many a cigarette or pipe around the world today.11