Pre-Columbian cherry picking by the New York Times

A few weeks ago, the NYT published an article about pre-Columbian Amazonia. The journalist reported the discovery of pre-Columbian geometric ditches in the Brazilian Acre. These were actually discovered a decade ago and were already described in a book edited by Pärsinnen et al (2003) and again by Pärsinnen et al (2009) in Antiquity, who called them “geoglyphs”. Till today, no one knows what those ditches were excavated for. As Pärsinnen et al. (2009) say: “The function, or functions, of the geoglyphs remain a mystery”. However, the author of the NYT article says that this discovery shows that Amazonia was densely populated in pre-Columbian times and is “potentially upending the conventional understanding of the world’s largest tropical rain forest”.

But, how can we draw conclusions about how pre-Columbian Amazonia looked like on the basis of something that we don't even know what it is?

I can already hear the answer of those who are pushing for the idea of a densely populated Amazonia: it is not only the geoglyphs! What about the terra preta? And the high productive agriculture of the raised fields? And the complex societies of the upper Xingú?

Well, all these archaeological features have one thing in common: they are found in sites that cover a very small and often peripheral part of Amazonia. But, let’s explore these arguments one by one.

Terra preta:

Terra preta is an organic anthrosol that is found in small patches (normally less than 2 hectares) distributed on the bluffs of large Amazonian rivers. Terra preta indicates the presence of pre-Columbian settlements. But it does not say how many people were living there at any given time or how complex those groups of people were from a social point of view. Many publications put together terra preta and terra mulata under the same label of Amazonian Dark Earth (ADE) and then speculate about large areas of high productive soils. But Terra preta properties cannot be extended to terra mulata (which, for example, has far less phosphorous compared with terra preta and lacks the pottery). As I have already discussed here and here, the claims about terra preta being the product of intentional transformation of soil for high productive agriculture have no scientific basis. Glaser and Birck (in press), who are among the greatest experts of the geochemical properties of terra preta, say in their latest paper “there is no scientific evidence indicating that forgotten agricultural techniques for large scale soil fertility improvement are responsible for terra preta genesis.”

Raised fields:

The high productivity of raised field agriculture in South America has never been demonstrated. I wrote a paper about this last year (Lombardo et al. 2011) were it is shown that raised fields in the Bolivian Amazon (which is, by far, the place with the highest amount of raised fields in Amazonia) were built to avoid water logging during periods of extreme precipitations. They were not a pre-Columbian green revolution but a means to adapt and survive in an unfriendly environment.

The Upper Xingú (Heckenberger, 2003):

In the upper Xingú, as Meggers (2003) puts it, the “clear evidence” of complex and large societies is anything but clear: “Heckenberger et al. state that domestic remains cover about 50 to 60% of the ditched areas and would represent 10 to 24 houses with 12 to 16 occupants each, but provide no archaeological evidence for these estimates.”[...] “Heckenberger et al. assert that “Xinguano cultivation and land management…provides a viable alternative” to modern clear-cutting strategies, but they do not describe them.” […] “Even if Heckenberger et al.'s analysis were acceptable, it would have no bearing on the controversy over the pre-Columbian existence of dense settlements and complex social organization in Amazonia. Like other regions with ditches, causeways, and mounds (the Llanos de Moxos, Bolivia; Acre and Marajó, Brazil; and the western Llanos, Venezuela), the Upper Xingu is environmentally and geographically peripheral to the rainforest. “

This last quote is probably the most important. In fact, even if we consider all the archaeological sites as evidence of pre-Columbian complex societies, they are all located in the peripheral regions of Amazonia or along the river floodplains called varzea, the belt of seasonally flooded areas that flanks the Amazonian rivers. Varzea accounts for only the 2% of the Amazon Basin. The problems of extrapolating from these few sites to the whole Amazonia have been extensively discussed by Bush and Silman (2007) and more recently by McMichael et al (2011) and Barlow et al (2011). Based on lake sediments and charcoal distribution analyses, these researchers conclude that human disturbance in Pre-Columbian Amazonia was localized. As Mark Bush, from the Florida Institute of Technology, clearly states: “It is very unlikely that the majority of Amazonia was strongly impacted by human activity.” (PDF of his talk here). In the words of Barlow et al. (2011): “We therefore urge caution before presuming that findings from a few well studied regions can be extrapolated to the entire Amazon, and reject the idea that the pristine myth has been thoroughly debunked by archeological evidence. Instead, we suggest that the influence of historical peoples occurred along gradients, with high impacts in settlements and small and scattered Amazonian Dark Earths, moderate impacts where enrichment planting occurred or where forests were affected by anthropogenic wildfires, and finally a largely imperceptible footprint from subsistence hunting and resource extraction across vast tracts of Amazonian forests that are far from permanent settlements and navigable rivers ”.

How is it possible that the NYT’s journalist, while writing his piece, didn’t bump into any of these papers?

William Woods, a geographer at the University of Kansas, is quoted by the NYT saying: “If one wants to recreate pre-Columbian Amazonia, most of the forest needs to be removed, with many people and a managed, highly productive landscape replacing it”. But, I think that before the scientific community accepts the idea that Amazonia was a highly productive anthropogenic landscape we need far more evidence than rectangular ditches in the Acre and patches of anthrosol.

Post scriptum

All this has important implications for our understanding of the resilience of Amazon ecosystems and the scale of deforestation in pre-Columbian Amazonia. Understanding how resilient Amazon ecosystems are can help inform present and future development and conservation policies for the region. If, as some authors suggest, there was considerable human disturbance in pre-Columbian Amazonia, then we can conclude that Amazonia is highly resilient and that the current degradation of its ecosystems may be reversible. On the other hand, if this resilience is overestimated, then mistaken policies can lead to irreversible loss of biodiversity and ecosystem services (Bush and Silman, 2007). Understanding the extent of pre-Columbian human disturbance of Amazonia is a prerequisite in order to assess the possible influence that post-contact re-forestation had on global climate. It has been estimated that pre-Columbian population in Amazonia fell by 95% after the spread of diseases that followed the arrival of the Spaniards. This sharp fall in population would have meant that large areas under cultivation before the conquest were abandoned and re-colonized by the rainforest. As Amazonia is one of the largest terrestrial players in the global carbon cycle, it has been suggested that the reforestation that followed the conquest could have sequestrated enough CO2 from the atmosphere to become an important factor in triggering the Little Ice Age. More on this here.

References

-Bush, M. B., and Silman, M. R., 2007, Amazonian exploitation revisited: ecological asymmetry and the      policy pendulum: Frontiers in Ecology and the Environment, v. 5, no. 9, p. 457-465.
-Glaser, B., and Birk, J. J., In Press, State of the scientific knowledge on properties and genesis of     Anthropogenic Dark Earths in Central Amazonia (terra preta de Índio): Geochimica et Cosmochimica Acta.
-Heckenberger, M. J., Kuikuro, A., Kuikuro, U. T., Russell, J. C., Schmidt, M., Fausto, C., and Franchetto, B., 2003, Amazonia 1492: pristine forest or cultural parkland?: Science, v. 301, p. 1710-1714.
-Lombardo, U., Canal-Beeby, E., Fehr, S., and Veit, H., 2011, Raised fields in the Bolivian Amazonia: a prehistoric green revolution or a flood risk mitigation strategy?: Journal of Archaeological Science, v. 38, no. 3, p. 502-512.
-Meggers, B. J., 2003, Revisiting Amazonia Circa 1492: Science, v. 302, p. 2067.
-Pärssinen, M., Schaan, D., and Ranzi, A., 2009, Pre-Columbian geometric earthworks in the upper Purús: a complex society in western Amazonia: Antiquity, v. 83, p. 1084-1095.

-McMichael, C., Bush, M., Piperno, D., Silman, M., Zimmerman, A., & Anderson, C. (2011). Spatial and temporal scales of pre-Columbian disturbance associated with western Amazonian lakes The Holocene, 22 (2), 131-141 DOI: 10.1177/0959683611414932
-Barlow, J., Gardner, T., Lees, A., Parry, L., & Peres, C. (2011). How pristine are tropical forests? An ecological perspective on the pre-Columbian human footprint in Amazonia and implications for contemporary conservation Biological Conservation DOI: 10.1016/j.biocon.2011.10.013

The Climate War

Climate is changing. This is like an obvious conclusion if you are old enough to remember how it was only 20 or 30 years ago. “Non c'è più la mezza stagione” (“There are no more middle seasons” which is the Italian equivalent of “Things are not what they used to be”) is one of the most used expression when travelling on the train in Italy, like a mantra used to start any conversation.

Less commonly accepted among the general public is that the cause of this change towards a warmer climate is CO2 (and other greenhouse gases) we humans release into the atmosphere. It is not uncommon to hear people say this is not true. Many, not only in the USA, think that “the left-wing political agenda is behind the global warming (GW) hoax”. What is quite surprising is that among scientists there is not such a controversy. All climatologists (but a few outliers…) agree on the fact that anthropogenic gases are responsible for the GW. So, how is it possible that we have such a schizophrenic society in which scientists and the general public have different opinions on scientific issues? If the public do not base their opinion about science on what scientists say, where do those opinions come from?

Well, there is now a very interesting book on sale that explains it all. The Hockey Stick and the Climate Wars: Dispatches from the Front Lines, by Michael Mann. Mann is a climatologist who has been involved, for the last 10 years, in the big battle that is being fought between scientists, on one side, and conservative journalists, politicians and corporations on the other side. I really enjoyed reading it for several reasons: you get quite a good understanding of how Science works; you end up learning a lot about climatology and you get a thorough historical reconstruction that provides you with a fair answer to the questions above. If you have sufficient economic means, you can take one of the basic principles of science (nothing is “true”, everything is under scrutiny) and sell it to the public as “they don’t know what they are talking about”.

I strongly recommend the book. If you are a scientist or you already know enough about climate science, this book can offer you a valuable historical reconstruction of one of the saddest examples of what happens when Science falls under political intimidation. If you belong to those who still do not have a clear idea about what is going on with the so called “climategate”, or who call themselves “sceptical”, this book can give you a precise idea of what the “climategate” actually is and will make you far less “sceptical”. On the other hand, if you believe that GW is a liberal hoax, don’t buy the book. Science is not for “believers”. Science is for the real sceptical, who can change idea once enough evidence is provided.

Ref.

The Hockey Stick and the Climate Wars: Dispatches from the Front Lines by Michael E. Mann

Mann, M., Bradley, R., & Hughes, M. (1998). Global-scale temperature patterns and climate forcing over the past six centuries Nature, 392 (6678), 779-787 DOI: 10.1038/33859

What is Amazonia?

This is not a trivial question.  Researchers writing about Amazonia very rarely provide a  definition. This ambiguity has important research implications, as often when discussing Amazonia those involved have different ideas of what is being discussed…  For example, In Meggers’ paper which I reviewed in my previous post, she disagrees with another archaeologist’s definition of Amazonia. Erikson, in his article entitled “Amazonia: the historical ecology of a domesticated landscape”, refers to Amazonia as “the entire region drained by the Amazon River and its tributaries”(Erickson 2008: 158). So, how would you define Amazonia? You could say, like Erickson , that it coincides with the basin of the Amazon River, but then you would be including a big portion of the Andes. But glaciers located 6000 m.s.l. don’t match  our idea of a lush Amazonia, do they? Another option could be to consider Amazonia only that part of the Amazon Basin that is covered by rainforest. Well, this looks better, but you would exclude important areas like the savannahs. Moreover, the size of the rainforest changes over time: the boundaries of the rainforest we see today are different from those it had 15000 years ago, and, with the expansion of industrial agriculture, forested areas have been shrinking significantly in the last 20-30 years. It is very unpractical to have to change the limits of what we call Amazonia each time the boundaries of the rainforest move. Meggers (2011) states that: “Amazonia is defined by geographers and ecologists as the portion of tropical lowland South America below 1,500 meters, where the average difference in annual temperature does not exceed 5ºF, rain falls on 130 or more days of the year, and relative humidity normally exceeds 80%. Typical vegetation consists of rainforest, with small enclaves of savannah where soil conditions inhibit plant growth.” However, she doesn’t say who are these “geographers and ecologists” and does not provide any references for this.

While looking for a good paper that defines Amazonia I found out that the European Commission, in collaboration with the Amazon Cooperation Treaty Organization, created in 2005 a task force of experts with the objective of defining the geographical boundaries of Amazonia. Scientists from different disciplines, such as climatology, hydrology, botany, zoology, ecology and biogeography, came together in a two day workshop to reach a consensus (Eva et al. 2005).

The criteria used to draw the map of Amazonia (Fig. 1) were Hydrography, Ecology and Biogeography.

You can download the study here

Figure 1 -

UNIT I = Amazon and Tocantins river basins [“Amazon Basin” or “Hydrographical Amazonia”]

Ia = Lowland rainforest biota of the Amazon and Tocantins River basins [“Lowland Amazon

Basin rainforest” or “Amazonia sensu stricto”]

Ib = Andes (non-lowland biota of the Andean Amazon Basin, > 700 m asl)

Ic = Planalto (non-lowland biota of the southern Amazon Basin)

UNIT II = Amazon lowland rainforest types outside Unit I

IIa = Guiana

IIb = Gurupí

Ia + IIa + IIb = Entire Amazon lowland rainforest biome [“Hylaea” or “Amazonia sensu lato”]

I + II = Amazon and Tocantins river basins + Amazon lowland rainforest biome outside the basin

[“Amazonia sensu latissimo”]

As you see in Fig. 1, they have defined Amazonia sensu stricto (the “real” Amazonia) as the area enclosed by the polygon Ia; and Amazonia sensu lato as the area enclosed by the polygons Ia+IIa+IIb (it is not the “real” Amazonia but you can call it Amazonia because it all looks alike). It would be great if, from now on and to avoid misunderstandings, archaeologists, geographers and paleoecologists that work in Amazonia could use this definition.  Eva et al. have provided us  with valuable operative tools that we can all use. Unfortunately, the European Commission forgot to make their file of the Amazonian boundaries available for download! I have been looking for it everywhere, but haven’t found anything. I asked for it through the EC web page, but I got no answer. A bit disappointing, considered that we paid for it!

Anyway, as I wanted to have a file that can be used in ArcGis, I resolved to digitalize the map of Amazonia myself. I also decided to distribute it. But, for now, you have to contact me via e-mail because I don't know yet how to upload it :-). I will put a link as soon as I figure out how to do it. I hope there is no copyright infringement in this… well, if there is, they will say something …

References

Erickson, C. L. 2008. Amazonia: the historical ecology of a domesticated landscape. In Handbook of South American archaeology, eds. H. Silverman and W. H. Isbell, 157-183. Berlin: Springer.

Meggers, B. J. 2011. Handbook of South American Archaeology Reviewed by Betty J. Meggers. Revista de Antropología Chilena 43 (1):147-157.

Eva, Hugh D., Huber, Otto, Achard, Frédéric, Balslev, Henrik, Beck, Stephan G., Behling, Hermann, Belward, Alan S., Beuchle, René,, Cleef, Antoine M., Colchester, M., Duivenvoorden, Joost F., Hoogmoed, Marinus Steven, Junk, Wolfgang Johannes, Kabat, P., Kruijt, Bart, Malhi, Yadvinder, Müller, Jan Marco, Pereira, José M. C., Peres, Carlos, Prance, Ghillean, Roberts, John, & Salo, Jukka (2005). A proposal for defining the geographical boundaries of Amazonia Office for Official Publications of the European Communities : EUR 21808-EN

Review of Betty J. Meggers‘ review of the Handbook of South American Archaeology

Betty J. Meggers has been working in Amazonian archaeology for more than 50 years. She has recently published a review of the Handbook of South American Archaeology, which is of great relevance to all of us working on the paleoecology of Amazonia during the Holocene. You can download her paper here.

The paper discusses 3 fundamental aspects of the South American archaeology: i) how contemporary Amazonian archaeologists’ interpretation of the archaeological record has been biased by the abandonment of the classical archaeological methods of pottery analysis; ii) the origin of new world pottery and iii) the relationship between environmental conditions and cultural development in Amazonia.

Classical archaeologists spent months on end drawing and analysing thousands of pieces of pottery. In the first part of her paper, Meggers explains why this meticulous work is a fundamental step in scientific archaeology: “Pottery can be decorated using an essentially unlimited number of techniques and motifs without affecting the utility of the vessel, making independent duplication of identical decoration unlikely”. Therefore, the analysis of pottery’s details and decorations allows us to distinguish diffusion (cultural aspects which are transmitted form one cultural group to another) form independent invention, where a cultural trait arises spontaneously in a given population. According to Meggers, some of the authors of the Handbook omit this important task, undermining the strength of their interpretation of archaeological records

Pottery analysis is the criteria that Meggers uses to discuss, in the second part of her paper, the origin of new world pottery. Many archaeologists that have contributed to the Handbook believe that pottery was independently invented in Amazonia. In Meggers’ view, the similitudes between Japanese Jomon pottery and the Valdivia pottery (which is the oldest pottery in America, dating 6000 BP) are too many to be the result of some form of “cultural convergence”. Moreover, she highlights that the period of Valdivia pottery coincides with a catastrophic volcanic eruption in Japan, which could have pushed groups of Japanese fishermen towards the American coasts. Hence, these Japanese fishermen would have influenced the pottery of early Americans. .

In the Handbook, Amazonia is depicted as a “manufactured landscape” or “anthropogenic cornucopia”. In the third part of her paper, Meggers assesses whether or not such descriptions of Amazonia are supported by the archaeological evidence. She shows that the evidence is actually very weak: the idea of widespread human occupation of pre-Columbian Amazonia is not supported by pollen, phytolith and charcoal analysis, which indicate that vast areas of Amazonia have never faced human disturbance; no systematic archaeological excavation has ever been performed that supports the assumption that large permanent settlements were common in Amazonia; many of the earthworks often cited in support of the “manufactured landscape” idea are concentrated in the Llanos de Moxos, which are ecologically quite different from the tropical rainforest that covers most of the Amazon basin; there is no evidence suggesting that ADE was created for intensive agriculture or to exclude that slash and burn agriculture was a common practice among pre-Columbian people.

Despite the fact that the bibliography of Meggers’ paper is not as large as it could have been, it can still serve as a good introduction to the archaeology of Amazonia for anyone who wants to get into the heart of the current debates.

Betty J. Meggers (2011). Handbook of South American Archaeology reviewed by Betty J. Meggers Revista de Antropología Chilena, 43 (1), 147-157

Special Issue: Environmental changes and pre-Columbian human influence in the Amazon region

The last number of Geographica Helvetica is a special issue about Amazonia entitled “Environmental changes and pre-Columbian human influence in the Amazon region”. Among the authors there are two prominent pollen specialists, Behling, H. and Mayle, F.E.; the phytogeographer Langstroth, R.; and several members (and ex members) of the paleo-geoecological group at Bern University, including myself. Abstracts can be accessed here.

Our paper, co-authored by Canal-Beeby, E. and Veit, H., is entitled “Eco-archaeological regions in the Bolivian Amazon. An overview of pre-Columbian earthworks linking them to their environmental settings”.

The discovery of extensive pre-Columbian earthworks in north-eastern Bolivia has been seen as evidence that Amazonia was once densely populated by complex societies. This has led some scholars to believe that culture evolved in Amazonia regardless of environmental constraints. However, this view does not take the diversity of earthworks and geo-ecological regions into account, nor their uneven distribution. This paper offers an initial explanation of the possible links that exist between the different types of earthworks in north-eastern Bolivia and their environmental settings and identifies six distinct eco-archaeological regions. Results show a spatial overlap between those areas with greater evidence of past complex societies and areas where environmental constraints were fewer. This suggests that local hydrology and soils influenced the development of pre-Columbian societies in the region.

Lombardo, U., Canal-Beeby, E., & Veit, H. (2011). Eco-archaeological regions in the Bolivian Amazon. An overview of pre-Columbian earthworks linking them to their environmental settings Geographyca Helvetica, 66 (3), 173-182

The extent of human disturbance in pre-Columbian Amazonia

Understanding the extent to which pre-Columbian peoples altered and deforested the Amazon basin is key in order to assess i) the impact that pre-Columbians had on global climate during the Holocene [Dull et al., 2010] and ii) the resilience of the Amazon rainforest to human disturbance [Bush and Silman, 2007]. The first point is essential to our understanding of the major drivers behind climate fluctuations during the Holocene, and hence to help predict future fluctuations. The second point is important to inform conservation and development policies in Amazonia. Unfortunately, the scarcity of archaeological and paleoecological data from the Amazon Basin has favoured the proliferation of “reconstructions of the past” that are hard to test.  Some of these theories have reached broad audiences thanks to the echo provided by popular media and books [Mann, 2005]. New archaeological findings that suggest the existence of complex societies in pre-Columbian Amazonia have led some researchers to define the Amazon Basin as a “manufactured landscape” or an “anthropogenic cornucopia” [Balée and Erickson, 2006; Erickson, 2008].  There are 3 different lines of research that can help assess whether or not these reconstructions are accurate. One is to focus on those regions that host important archaeological remains and study the evidence of complex societies. This work is already being carried out by some archaeologists such as Heiko Prümers. The second area of research is to examine if and how the development of complex societies in the region were influenced by local environmental constraints and opportunities. This is the kind of work that I am carrying out in the Llanos de Moxos and  hope to discuss in another post quite soon J (briefly introduced here…). Another area of research that can help us understand the Amazon’s past is to test if the level of human disturbance associated with the sites where evidence of complex societies has been discovered can be extrapolated to the rest of the Amazon basin.  A milestone paper that looks at the latter, and that has been often cited in this blog, is Bush and Silman (2007).

A few weeks ago, The Holocene published on-line a new paper that delves deep into this question, providing interesting new data [McMichael et al., 2011].  McMichael et al. test the hypothesis that human disturbance was widespread in the Amazon Basin during pre-Columbian times (as some authors have suggested). If this hypothesis is true and the disturbance was widespread then, the authors argue, the sites where permanent settlements were likely to have established should show sedimentary evidence of that disturbance. Hence, they cored lakes (considered by the authors as preferred settlement sites) and sampled soils in the vicinity of the lakes and looked at charcoal and phytoliths. They found that charcoal record was discontinuous and localized. They then concluded, based on the sedimentary evidence: “Our data suggest that while all of the settings examined were occupied or used, the halo of influence around each was limited. It should not be assumed that intensive landscape transformations by prehistoric human populations occurred throughout Amazonia or that Amazonian forests were resilient in the face of heavy historical disturbance”. The paper suggests that pre-Columbians developed into complex societies and substantially altered their environment in those areas where environmental conditions were favourable. They predict that these sites can be found along the main rivers and in those parts of the Amazon Basin that are characterized by a strong seasonality (like the Llanos de Moxos).

In my opinion this paper is a beautiful piece of Science and I invite you to read it!

References:

Balée, W., and C. L. Erickson (2006), Time, complexity and historical ecology, in Time and complexity in historical ecology: studies in the neotropical lowlands, edited by W. Balée and C. L. Erickson, pp. 1-17, Columbia University Press, New York.

Bush, M. B., and M. R. Silman (2007), Amazonian exploitation revisited: ecological asymmetry and the policy pendulum, Frontiers in Ecology and the Environment, 5(9), 457-465.

Dull, R. A., R. J. Nevle, W. I. Woods, D. K. Bird, S. Avnery, and W. M. Denevan (2010), The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing, Annals of the Association of American Geographers, 100(4), 755-771.

Erickson, C. L. (2008), Amazonia: the historical ecology of a domesticated landscape, in Handbook of South American archaeology, edited by H. Silverman and W. H. Isbell, pp. 157-183, Springer, Berlin.

Mann, C. C. (2005), 1491 New revelations of the Americans before Columbus, Vintage books, New York.

C. H. McMichael, M. B. Bush, D. R. Piperno, M. R. Silman, A. R. Zimmerman, & C. Anderson (2011). Spatial and temporal scales of pre-Columbian disturbance associated with western Amazonian lakes The Holocene : 10.1177/0959683611414932

About maize, manioc and agricultural production in pre-Columbian Amazonia

A new paper from Dickau et al., recently published on-line by the Journal of Archaeological Sciences, brings us back to one of the favourite themes of this blog: pre-Columbian agriculture in the Amazon Basin. The work of Dickau et al. confirms the findings of Bruno (2010), also a co-author in Dickau et al., and provides more data from new sites. They have analysed botanical remains from 2 pre-Columbian monumental mounds east of Trinidad (Loma Salvatierra and Loma Mendoza) and from another site, a ring ditched village called “Granja del padre”, about 200 Km far from the mounds, close to Bella Vista(see location in Fig 1 and photo of the ring village in Fig 1a). Analysis of macro and micro botanical remains from Loma Salvatierra and Mendoza and from Granja del padre suggests that the most common cultivated species was maize (Zea mais L.). It was present in almost all samples and fairly abundant. The second most common cultivated species seems to have been manioc  (Manihot esculenta Crantz). Interestingly, maize was also more frequently encountered on ceramic graters, which were thought to be processing tools for grating manioc . They recovered starch grains from artefacts and clearly identified 5 grain of yucca vs. 115 of maize.  This is really surprising because manioc is a good source of energy and far easier to cultivate than maize. Ceramic graters  can be found all over the Llanos. It can be easily assumed that manioc was cultivated all over the Llanos de Moxos because, provided good drainage, manioc can grow even on very bad, acid, aluminium rich soils. I was actually persuaded that raised fields, elevated earth platforms that were user as agricultural surface, were built to provide drained land for manioc. But now, it seems that maize, and not manioc, was the most important crop in the Llanos de Moxos.

Figure 1. The Llanos de Moxos. Red triangles are the Salvatierra and Mendoza mounds. a) Google Earth photo of the Granja del padre with the approximate locations of the archaeological excavations in yellow.

We have to consider that starch grain analysis is still a developing technique and the variables that affect preservation of different taxa are not yet fully understood. But, if this data is confirmed by other researches, we could start considering ceramic graters (Fig 2) as a proxy for maize consumption. As ceramic graters are found everywhere in the Llanos de Moxos, a direct link between ceramic grates and maize would indicate that maize was used all over the region.

Figure 2. Fragment of a ceramic grater from the Llanos de Moxos

This opens up a very interesting topic for future research: was maize cultivated in all the sites where it was consumed? This is not a trivial question because maize is a very demanding crop: it needs many nutrients and a lot of water, but rots if the soil is waterlogged. In the Llanos de Moxos soils and hydrology change a lot from one place to another. For example, while soils in the region of the Salvatierra and Mendoza mounds form over fertile mid-Holocene fluvial sediments (Lombardo et al. coming soon, I hope J ), la Granja del padre is found on saprolites (rotten granite rocks), very acid and poor in nutrients. Moreover, in the region of Bella Vista, no raised fields or Amazonian Dark Earths have been reported. So, did they grow maize using slash and burn agriculture? If so, this would have greatly limited potential population density in the area, as slash and burn agriculture is considerably extensive. Each family needs at least 30-40 hectares of forest for cultivation and far more as a reservoir for hunting and medicinal plants. Or was maize “imported” from other regions? Exchanged for other goods? The estimation of pre-Columbian population density, and the extent of pre-Columbian de-forestation, is a controversial issues among ecologists, geographers and archaeologists working in Amazonia. More studies like that of Dickau et al. are needed in order to shed some light on the past of Amazonia during the late Holocene. Their work adds important new data to the discussion, although we are still far from fully understanding what was going on in the Bolivian lowlands between 2000 and 500 BP.

Ruth Dickau, Maria C. Bruno, José Iriarte, Heiko Prümers, Carla Jaimes Betancourt Irene Holst, & Francis E. Mayle (2011). Diversity of cultivars and other plant resources used at habitation sites in the Llanos de Mojos, Beni, Bolivia: Evidence from macrobotanical remains, starch grains, and phytoliths Journal of Archaeological Science : 10.1016/j.jas.2011.09.021