America Before
Page 17
Indeed so! And even in these days of man-made ecological disaster let us remind ourselves that 5.5 million square kilometers of the Amazon basin is still covered by rainforest. To put that in perspective, picture Mexico, Guatemala, Belize, Honduras, and El Salvador. Taken together they encompass 2.22 million square kilometers32—not nearly enough—so we will need to add on India with its 2.97 million square kilometers to get an imaginary realm almost equivalent in size to the Amazon rainforest.33 My point here is that when we consider the Amazon as an archaeological project, its scale is comparable to Mexico, Guatemala, Belize, Honduras, El Salvador, AND India all added together, and all, in addition, entirely covered by dense rainforest and therefore difficult and expensive to access. Moreover, unlike Mexico, Guatemala, Belize, Honduras, and El Salvador, where the famous Maya civilization flourished, and unlike India with its ancient cities and temples, there was, as we’ve seen, no inducement for archaeologists to invest scarce time and money on excavations in the Amazon while it was believed that nothing of great interest would be found there. At the close of the second decade of the twenty-first century no serious archaeologists are still thinking that way! The state of affairs they’ve inherited, however, means that huge swaths of the Amazon, encompassing millions of square kilometers, have never been subject to any kind of archaeological investigation at all.
This is a wider problem than the Amazon. For example, sea level rose 120 meters when the Ice Age came to an end with the result that 27 million square kilometers of land that was above water at the last glacial maximum 21,000 years ago is under water today.34 These submerged continental shelves were prime seafront real estate during the Ice Age, yet only a few tiny slivers of them have ever been subject to any kind of marine archaeological investigation. Again, this is because, like the Amazon, access requires special preparations, equipment, and transportation and also because of a similar belief that whatever would be found as a result of these costly investigations would not add greatly to what is already known.
I’ll say nothing about Antarctica, with its 14 million square kilometers entirely virgin to the archaeologist’s spade.35 The almost universal agreement that humans could never have lived there in the past might or might not be correct, but we’ll never know for sure unless we look.
We do know that the Sahara desert, presently occupying an area of about 9 million square kilometers,36 had a very different climate during the Ice Age, and in the early millennia of the Holocene, than it experiences today and that there were long periods when it was well watered and fertile, with extensive lakes and grasslands and abundant wildlife.37 It is near enough to Egypt and the other great centers of early civilization in North Africa and the Middle East to have attracted the attention of archaeologists, but like the Amazon and like the submerged continental shelves, access is difficult and expensive, placing serious practical limits on what can be achieved.
Part of our predicament, therefore, as a species with amnesia, is that huge areas of the planet that we know for sure were used by and lived upon by our ancestors—the submerged continental shelves, the Sahara desert, the Amazon rainforest—have, for a variety of practical and ideological reasons, been badly served by archaeology. The truth is, we know VERY little about the real prehistory of any of these places, and the tiny patches that have thus far been surveyed and excavated within them are no legitimate basis upon which to draw conclusions and express certainties about the vast areas that remain unsurveyed and unexcavated.
Guatemala, in central America, was one of the six countries I suggested we put together to envisage the scale of the Amazon rainforest. Guatemala itself encompasses just under 109,000 square kilometers.38 It’s an indication of how pointless it is to take any so-called facts about the past for granted, however, that even in this tiny country, fifty times smaller than the Amazon, a huge archaeological surprise was unveiled in 2018.
“Everything is turned on its head,” commented Ithaca College archaeologist Thomas Garrison on the results of a survey of 2,100 square kilometers of Guatemala’s densely forested northern Peten region.39 Deploying Lidar (Light Detection and Ranging) pulsed laser technology, what the survey revealed, in areas quite close to known and even famous and well-visited Mayan sites such as Tikal, were more than 60,000 previously unsuspected ancient houses, palaces, defensive walls, fortresses, and other structures as well as quarries, elevated highways connecting urban centers, and complex irrigation and terracing systems that would have been capable of supporting intensive agriculture.40 Previously scholars had believed that only scattered city-states had existed in an otherwise sparsely populated region, but the Lidar images make it clear, as Garrison puts it, that “scale and population density had been grossly underestimated.”41
Katheryn Reese-Taylor, a University of Calgary archaeologist, adds:
After decades of combing through the forests, no archaeologists had stumbled across these sites. More importantly, we never had the big picture that this data gives us. It really pulls back the veil and helps us see the civilization as the ancient Maya saw it.42
When pulling back the veil on the relatively recent Maya civilization in a small part of the tiny country of Guatemala can produce so many surprises, we may begin to imagine what “big picture” might come to light if the vastly larger and more opaque veil that has covered the Amazon rainforest for so long were to be drawn back.
Hopefully the interest will be there and the funds made available for it to be drawn back thoroughly using the latest scanning technologies followed up by site surveys and excavations. Until that happens, however, no archaeologist is in any position to dismiss the possibility that the very old and very troublesome Australo-Melanesian genetic signal that has been detected among Amazonian populations might have gotten there by the “most parsimonious” route—namely, by a direct crossing of the Pacific from Australasia to South America.
That, in turn, would imply a civilization capable of great oceanic voyages and therefore by definition at a much more advanced stage of development than archaeologists are prepared to accept for any branch of humanity during the Ice Age.
BLACK EARTH
IT SEEMS TO ME TO be no longer in doubt that civilizations with true cities and mature polities did flourish in the Amazon before the European conquest. Less clear is how far back the story of these civilizations can be traced in this immense region where so little archaeology has been done.
Thanks to Anna Roosevelt’s work we know, at the very least, that humans were present at Pedra Pintada at the Tapajoz/Amazon confluence by about 14,000 years ago and possibly significantly earlier.1 With other more accessible painted rock shelters in Brazil dating back as much as 50,000 years, it is, I suspect, only a matter of time before evidence of at least equally great if not greater antiquity emerges from the Amazon itself.
But greater antiquity of what? Was it foragers and hunter-gatherers all the way back? Or was some advanced but unseen presence capable of spanning the globe at work behind the scenes of prehistory that might help to explain how Australasian genes reached the Amazon during the Ice Age? Again, the problem is complicated by the fact that few archaeologists other than Roosevelt have looked for evidence of humans in the Amazon at all at such a remote period, so we have very little to go on across thousands of years during which the data are sketchy and inconclusive.
But then out of that opaque interlude in the life of the prehistoric Amazon, quite suddenly and unexpectedly, the lineaments of a great mystery begin to materialize. It concerns the “exemplary agronomy” that UCLA’s Professor David Wilkinson cites as his two-word explanation for how the cities of the rainforest were able to feed their large populations—because rainforests in general do not have good base soils but sustain their fertility in the mulch of plants and leaves above ground.2 This is why, when areas of the Amazon are cleared for agriculture today—for example, to make way for soybean plantations—they become exhausted, infertile, and useless after only a few years.3 But Wilkinson is not speak
ing of the base soils. His “exemplary agronomy,” as we shall see, refers to an artificial, man-made soil that first suddenly and inexplicably appeared in the Amazon many thousands of years ago but that has such miraculous properties of self-regeneration that it is still in use for agriculture and still incredibly productive today.
It is called Terra preta. More than any other single factor, it is now understood by scholars to have been responsible for the astonishing and utterly anomalous agricultural productivity that allowed a population estimated at between 8 and 20 million people4 to thrive for untold epochs in the Amazon before being overtaken by the cataclysm of the European conquest.
Terra preta feels like the work of scientists, but if there was a civilization in the Amazon, then why should we be surprised to find scientific achievements to its credit?
THE MYSTERY
THE EXISTENCE OF TERRA PRETA was first reported by Europeans in colonial-period Brazil who called it terra preta de Índio (Indian Black Earth), “the reference to ‘Indians’ reflecting the presence of abundant pottery shards of evident pre-Columbian age on the surface of most known exemplars.”5 Today these special soils, described by one nineteenth-century explorer as consisting of “a fine, dark loam, a foot, and often two feet thick,”6 are more often spoken of as “Black Earth,” “Amazonian Anthropogenic Dark Earths,”7 or simply as “Amazonian Dark Earths”—ADEs for short.8
Whatever we call them though, what are they, and why do they matter?
We’ve seen how, across immense areas, the natural terra firme (non-floodplain) soils of the Amazon are too poor to sustain intensive agriculture and thus to feed the large-scale populations that we now know inhabited the region in pre-Columbian times:
With few available nutrients and having extremely high aluminum concentrations, one could not imagine a worse regime for productive agriculture.9
Indeed, the consensus of scholars is that even the floodplains with their better soils are high-risk areas for crop production “because of the unpredictability of the flood regime.”10
But, and it’s a big but, what are we to make of those early explorers’ reports of dense settlements extending for kilometers along river bluff edges whence roadways branched out into the interior?
The remnants of some of these settlements are now being investigated by twenty-first-century researchers, no longer blinded by the prejudices of the past, who often refer to them as “garden cities” of the Amazon.11 Invariably it turns out that they are associated, as one authoritative study puts it, with large acreages of “‘Indian black earth’ or terra preta. The heightened fertility status of these soils, generically termed ‘dark earths …’ has long been recognized by the indigenous inhabitants of the region, as well as by current colonists.”12
Across the rainforest there are many thousands of expanses of terra preta on a similar range of scales, covering a total area that is in all honesty unknown but that various authorities have guesstimated at 6,000 km2, 18,000 km2, 154,063 km2, and “an area the size of France” (i.e., around 640,000 km2).13 Whatever the true figure, these widely scattered plots of ADE—the rediscovered remnants of a once much more extensive system—are indeed actively sought out and productively cultivated by indigenous people to this day.
In the southeastern Amazon along the Xingu River, to give just one example, a recent study found that existing settlements, though on a much smaller scale than in the past, are still able to survive largely because of the accomplishments of their ancestors who had “continuously occupied, managed and modified” the soils over thousands of years. Almost without exception the riverine people of the Xingu today “inhabit and plant in dark earths,” and make use of resources, such as “Brazil nuts, babassu palm, dark earths and vine forests” that are “indicators or products of this earlier occupation.” Indeed, as Stephen Schwartzman, the research team leader, maintains, “Contemporary land use and resource management in the Xingu corridor is … significantly conditioned or made possible by mostly little-studied prehistoric land-use practices.”14
Particularly little studied and poorly understood are the practices that resulted in the so far unexplained inception in the Amazon, a very long time ago, of the incredibly fertile ADEs themselves. Nobody doubts that they are “anthropogenic”—man-made in some way15—and everyone agrees that they’re an amazing success story. So fecund is terra preta, even after thousands of years of use, that it can still regenerate barren soils it is added to, and has been described as “miracle earth.”16
The important questions therefore, are how was terra preta made, why was it made, when was it made, and who made it?
Part of the answer to the first question is often dug up by villagers along the Xingu River. In (and characteristic of) the patches of ancient terra preta where they plant their crops they “regularly encounter potsherds, stone axes, ceramics and figurines.”17
Such “refuse” left behind by people of the remote past, seems to play an important role in the amazing fertility of the ADEs—but then so do all the other strangely jumbled and juxtaposed ingredients that typically also include compost, the feces and urine of humans and animals, and all sorts of organic “kitchen” waste, including bones, notably fish bones.
Most researchers believe that terra preta soils formed as composted material accumulated via incidental human activity (often in debris piles referred to as middens).18
University of São Paulo archaeologist Eduardo Neves reportedly favors a scenario in which successive generations could have swept food refuse—especially fish and animal bones—from their dwellings and then added human and animal excrement.19
Elsewhere, in a paper published in the Journal of Archaeological Science in February 2014, Neves, Michael Heckenberger, and others develop this idea further. Their argument depicts the ancient Amazonians as living amid a shitscape (euphemistically referred to as a “middenscape”),20 dumping their excretions, rubbish, broken crockery, and fish bones into the middens and—most importantly—burning wet vegetation on top of the middens, and always conscientiously making sure, without any long-term planning or purpose in mind, to keep the fires damped down under a blanket of dirt and straw.21
This method of cool-burning, explains Tom Miles, an expert in the combustion and gasification of biomass,22 is known as “slash-and-char”—to distinguish it from the widely condemned “slash-and-burn”:
In slash-and-burn, dry brush and grass are burned in open fires, spewing vast quantities of carbon dioxide into the atmosphere and leaving only small amounts of nutrients in the ash that’s then dug into the ground.
By contrast, slash-and-char involves burning wet vegetation, so it smoulders underneath a layer of dirt and straw. Robbed of oxygen, the fire only partly burns any wood or stalks, leaving most as tiny chunks of charcoal. This bio-char is turned into the soil.23
In due course—entirely incidentally and accidentally according to most proponents of such views—these stinking, smouldering middens spread and alchemically transformed themselves into ADE, “the world’s most fertile soil,”24 without any deliberate human intervention at all.
I’d say it’s an unlikely story!
I can’t prove it but my bet is that terra preta is not an accidental by-product of shit, fish bones, broken pots, figurines, stone ax heads, and low-temperature fires. Just because it contains all those things doesn’t inevitably make it fortuitous. I think the evidence supports another possibility—that this remarkable soil was invented, making excellent use of freely available local resources, as an ingenious, low-tech, and environmentally friendly way to increase agricultural yield in areas that would otherwise not have been able to sustain agriculture, and thus large populations, even for a few decades, let alone for several thousands of years—as the Amazonian Dark Earths have consistently demonstrated a “miraculous” ability to do.
“What has been mysterious about these soils,” Professor Antoinette WinklerPrins, director for environmental studies at Johns Hopkins University, admi
ts, “is their ability to persist in a landscape that common ecological knowledge would dictate they could not.25… Why then have ADE’s dated to have formed up to 2500 years ago, continued to exist?”26
It is not just a matter of 2,500 years ago—as we shall see, the origin of the Amazonian Dark Earths goes back much farther than that—but here’s how Dr. WinklerPrins answers her own question:
The unique nature of the carbon in these soils is the key to the stability of the organic matter in ADE’s and the key to the mystery of the persistence of ADE’s in this landscape.27
There appears—exceptionally—to be universal agreement among scientists on one point. This is that the explanation for all the useful qualities of terra preta “lies in large part with the char (or biochar) that gives the soil its darkness” and that is produced, as Tom Miles explained, by the smouldering (rather than hot burning) of organic matter in an oxygen-poor environment. The results are not properly understood, but, according to Nature, “The particles of char produced this way are somehow able to gather up nutrients and water that might otherwise be washed down below the reach of roots.”28
William Balée, professor of anthropology at Tulane University, confirms these observations, adding that “microbial activity leads to increased carbon sequestration,” and that “ADE is richer and more diverse in microbes than surrounding soils, even though millions of these species remain to be identified precisely, and literally a million separate taxa can be contained in only 10 grams of soil. A significant proportion of the microbes in ADE are different from microbes in the surrounding primeval soils.”29