Thursday 14 November 2013

Origins of Rice Podcasts

Last week, before typhoon tragedies hit the Philippines, I joined about 700 geneticists and plant breeders working on rice for the Rice Genetics 7 symposium, organized by IRRI. and I was very proud to present our current archaeological picture on the origins and spread of rice in Asia to a packed auditorium the first morning. I also had the opportunity to take part in an IRRI radio podcast on the "Origin of Rice" for a ~5 minute version also featuring Prof Sudan McCouch go here . For the extended 14-minute version on archaeobotany try this link.

Monday 15 July 2013

The eastern fertile crescent returns

The recent paper in Science by Riehl et al. on  the evidence for Chogah Golan has rightly garnerd wide attention (e.g. Science news; commentary by Willcox). This is a highly significant paper, which shows that the beginnings of cultivation were indeed mutlicentric within the fertile ccrescent, and it suggests that there was an independent domestication process for emmer wheat in the eastern fertile crescent in addition to that in the western fertile crescent. 

Are there surprises? Yes. The big surprise here is the emmer wheat domestication, as many have argued on biogeographical and modern genetic grounds that there should have been and eastern and western barley domestication, but this has been little considered for wheat. This is mainly because the modern distribution of wild wheats does not extend that far east and south, and thus the data from the Chogha Golan, especially the lower levels indicates that the distribution of wild wheats at the start of the Holocene/end of the Pleistocene was indeed different and more extensive than modern wild wheats. This further implies that some starts to cultivation and domestication events could have drawn on wild population that are extirpated today and therefore are not reflected in modern wild germplasm collections. Modern collection used in genetic studies are only a fragmentary representation of the past, although geneticists often fall into the trap of assuming that good wild sampling in the modern day means they have captured the wild diversity from which domestication began.

What this what we/ I suspected? Yes. I am one of a number of scholars who have been arguing for a multicentric process of parallel starts to cultivation and parallel, and protracted, domestication processes around the Fertile Crescent, i.e. De-centering the Fertile Crescent. Mostly we have argued this on contrasts between the Southwest and the north/central fertile crescent and the contrasts between morphological diversity in archaeological samples and that in modern germplasm. As the authors here note with their triticoids, they are dealing with a wild wheat type not well represented in modern collections; this is equally true of early domesticated wheats in Syria/Anatolia and even in Neolithic Europe. In the Neolithic there are extinct genetic lineages, that are morphologically distinct, that are not found in modern landraces. In other words there are several lost crops of early agriculture. 

Were things really synchronous? This remains a little unclear. The lower levels seems to have pre-domestication cultivation of barley and lentil and lost wild wheat in the equivalent of PPNA/ EPPNB time periods-- this is indeed the same period that we see this in Jordan, Israel, north and south Syria. However in the Chogha Golan there is then a break and a large minority of domesticated type emmer appears. But this is mainly in the Late PPNB (ca. 7800 BC)! By this period domesticated crops are well established at higher frequencies (usually 60-70% non-shattering spikelet bases) in western fertile crescent assemblages (mainly of einkorn wheat or barley). Emmer at Tell Aswad in Syria is ~23% non-shattering at 8300 BC and at Tell el-Kherkh in NW Syria it is 44% at ca. 8400 BC. This evolution of non-shattering (a key domestication trait) appears  slightly ahead in the west. This could mean the that 25%-domesticated assemblage at upper Chogha Golan has spread from early cultivated population elsewhere that were undergoing the gradual selection for non-shattering, or it could indicate a local process, maybe not at Chogha Golan, but nearby that simply got started a bit later. 

I would note in passing, that there was one previous suggestion of eastern emmer domestication, many years ago by Hans Helbaek in the 1960s based on rather poor samples collected by the Braidwood expedition at Jarmo in Iraqi Kurdistan in the 1950s, in which Helbaek reported intermediate types and mixtures of wild and domesticated emmer. These data were never quantified nor fully published but would potentially fit with the Chogha Golan finds. So a return to Jarmo may yet have some important archaeobotanical contributions to make.

On the whole, however, these new data offer strong support from a new dataset and a different research group for what I have been championing as a paradigm shift in agricultural origins research. From the paradigm of a rapid and singular agricultural revolution to a paradigm of protraction and entanglement that was messy and non-centric. (See, e.g. refs 2 and 19 cited by Riehl). 

Tuesday 7 May 2013

Used Planet

Last week saw the publication of "Used planet: a global history" in PNAS [pdf] in which I teamed up with some land use and palaeoenvironmental modellers to offer an alternative synthesis of the evidence for human environmental modification. Much of the time in studies of land use and environmental change it is assumed that major environmental change and destruction is quite new, something brought on by the industrial era in the last few hundred years. Land use models like the HYDE model illustrate this, with something that approximate the projection of modern population: land use ratios backwards to periods when very few people were around. The key authors of the original HYDE model were part of this paper, and are quick to point out the many uncertainties and flaws in the HYDE dataset and its application (as in this recent paper). This is illustrated by the graph on the left (above) with most of the transformed land (in light purple) only dating to the past few centuries). By contrast in a model that assumes landuse intensification fewer people used land more extensively and only more intensively as rising population forced them to (the right hand charts above). Comparing maps of these different models, makes it look like "two different planets"  (to quote the blog of lead author Erle Ellis). Whereas archaeologists and anthropologists have debating and modifying Boserup's intensification concept or the notion of "agricultural involution" of Geertz for decades, this seems to have came rather late to global climate and land use modelling studies. Intensification in the use of all sorts of things has been a hallmark of human prehistory, from the broad spectrum revolution, the development of post-harvest intensification, in the use of grinding stone and other cook techniques (explored elegantly by Wollstonecroft 2011), the development of pre-harvest intensification (i.e. cultivation), improved yields through the evolution of domestication traits (with its own new labour demands, a kind of intensification too, see, e.g. my "domestication as innovation" paper), and agricultural intensification as it is normally defined (on which, see Morrison 1994). That our review of these two planets, which fairly clearly comes out in favour of one in which transformations by people are old and intensification processes are long-term, catches some sort of zeitgeist, is suggested both by the press coverage of this paper in New Scientist, Scientific American and The, and a session devoted to the same theme at last months SAA (summarized by Michael Balter). Of interest is that the latter two take the younger "impact" date of 3000 years, while the former takes 5000 years (I guess on my suggestion). One of the things that came up in discussions that lead to this coverage is what kind of impacts were there and when should we put the start of the "Anthropocene." 

From Early Holocene impacts to the Anthropocene

Should we replace "Holocene" with "Anthropocene"? Some might tend towards this view, since the start of Holocene is afterall when cultivation began, i.e. human "niche construction" intensified. My own view was that while that was a watershed in human behaviour, it was a long time before cultivation got underway in most parts of the world, or even in those early centres, before it developed into true agriculture, cultivation at the scale that impacted landscapes and made economies that were basically dependent on domesticates, leaving little subsistence space or time for wild foods. Early impacts were not early Holocene but notably middle Holocene from around 6000 BC-1000 BC, and with increasing intensity.

To the put the early impacts into chronological perspective, I would make the following points. 8000 years ago represents the approximate point at which agriculture was established and agriculturally-supported permanent villages appeared in several parts of the world. This is the period of the first villages in China, focused on millet cultivation and with domesticated pigs on the North Chinese loess plateau and the Yellow river valley. This appear in several places from Gansu to Hebei to inner Mongolia. By this period there is clear evidence fo established cultivation of domesticated maize and squash in southern Mexico, and various crops being farmed on the northwest coast of Peru, peanuts among them, and these had there origins in Amzonia east of the Andes. In West Asia this is the period of well-integrated agroo-pastoral systems with a whole suite of crops (wheat, barley, flax, pea, lentil) and animals (cow, goat, sheep horse). This period (9000-8000 years ago) see the rise of not just permanent villages around the Near East but large "mega-sites", for example Catal Hoyuk in central Turkey, which supported permanent population in the 1000s (~6000 is one estimate of site's size). This may not sound big in modern terms, but when you consider that hunter-gather bands are on the scale of 30-40, with large seasonal gatherings at maybe twice or 3 times that at most (i.e. there were unlikely to ever be more than 100 people in one place at one time for even for a seasonal festival for the 150,000 or so years of Homo sapiens history prior to that), then a few 1000 people living together in one place, supported by local agriculture, is a big difference. 9000-8000 years ago is when farming started to spread from the Near East reaching Turkmentistan, Pakistan in the east by 8000 (which big permanent villages established in those areas) and reaching in SW Europe (Greece, and Balkans. The establishment of agriculture on several continents means sustained transformations of local landscapes and ecosystems. Of interest is that this roughly the time point at which some, such as Bill Ruddiman, have inferred that global carbon-dioxide level just start to divert from the expected interglacial trend (see his recent Earth & Planetary Sciences review paper and his Real Climate blog post). This lends extra importance to the 8000 BP landmark. Our paper is not about the greenhouse gas story, which involves lots of complicated factors of the carbon cycle, but we are certainly with Ruddiman in as much as one needs to factor human activities into the equation at that time when considering global carbon issues since 8000 years ago.

Another landmark for me is in the 5000 BP sort of timeframe. This is the period which sees the beginning of tropical savannah farmng, in subsaharan  Africa, inner India, also the central and eastern USA, mainland SE Asia. This sees the major spread of rice out of China and into SE Asia (see my previous blog), and the land area in the Old World (Africa and Asia) that support pastoralism (sheep, goat, cattle) doubling. This period sees the spread of agriculture with llama-keeping to high elevantions in the Andes, and by about 4500 BP the establishment of maize-beans-squash farming in the American southwest. In these more marginal environments the impact of early farming on erosion and local flora may have been more severe than in naturally better-watered regions. In the established agricultural centres (Mesopotamia, Egypt, the Yellow River, southern Mexico) this is the period in which the urbanism get establish (slightly later in Mexico perhaps) with all sorts of new demands on agricultural intensification and specialized production to support urban populations that do not carry out their own subsistence. The rise of major textile and metal industries at this time, especially well documented in Mesopotamia and Egypt, means larger herd of sheep that were not for eating, land for flax that was not for eating, and increase wood fuel demands for bronze furnaces (and new materials like Faience or in China proto-porcelains). Bronze is a bit later in China and SE Asia (after 4000-3500 years ago), but still falls into this time horizon generally. There is a new scale in deforestation to go along with the establishment of agriculture on all continents and subcontinent (except Australia or the polar regions). In Ruddiman's Greenhouse gas story this period is when global methane is meant to diverge from expected interglacial trends. In other words after 5000 BP both the greenhouse gases have started to look unnatural. He has hypothesized that this was to do with the spread of wet rice, and elsewhere (in a Holocene paper) I have argued that one also must count the cattle which spread like wildfire through the tropical savannahs of Africa, India and perhaps SE Asia at this time (see previous blog). This is also roughly the dairying revolution in Europe, not when people first used a bit of milk, but when people began to herd cattle to specialize in milk production (and European people evolved adult lactase enzymes): this may have also been a upturn in animal herd density. How human activities translate into greenhouse gases is complicated, because of interacting carbon sinks and sources, and not the point of the "Used Planet" paper, but the implication of out paper is that human activities should not be ruled as a contributing to global processes

By 3000 BP or so it is hard to deny human impacts, although I would put the significant shift earlier. In archaeological terms 3000 BP roughly corresponds to the Iron Age. The thing about Iron is that is much more egalitarian than copper alloys, in as much as Iron ores are really widespread and found in all regions. Mesopotamia had import copper from Oman or distant parts of Turkey, and time from Afghanistan. Africa south of Egypt and Nubia never really had a bronze age, nor did southern India, but they all took to Iron because iron ores were available. Everybody had iron ore on their doorstep. But iron smelting requires twice as much wood fuel (at least) as copper. One set of wood fuel just to turn wood into charcoal, and then charcoal represents a second set. So a upturn in wood demands and deforestation. There is no Iron Age in the Americas but Peruvian and Mexican metallurgy (copper, gold) are full swing by this time. The other thing about the centuries after 3000 BP is the upscaling and cities and the first empires. Think Assyrians, followed by Persians. The Qin emperor of China may not unify China until the 3rd c. BC but he comes at the end of process of expansionary attempts by various rulers ("The Warring States", etc). This is the era of Maya pre-classic (in southern Guatemala) and Olmecs (on the Gulf coast of southern Mexico), which represent first urban-like communities and kingdoms in Mesoamerica. In South America this period sees the arrival of farming on the shore of Lake Titicaca (which was to become a focus of intensive farming and urbanism of Tiwanaku about 1000 years ago), and first big ceremonial centres, foci of dispersed but farming growing populations, at sites like Chavin du Huantar. This period sees the founding of sites that were to development into cities in the Niger river in west Africa, the earliest phases at place like Jenne-Jeno and Dia. In short, all over the work human population densities increase, proportions of the populations not engaged in their own subsistence increase (but are still a miniscule minority bu modern western standards) and technologies requiring heavy wood fuel use increase in scale and global frequency. 

Time for Big Archaeology

When I was asked by the journalist from New Scientist where I put the start of the "Anthropocene" I suggested 5000 BP. By 3000 BP there is certainly no doubt (the date chose by the headlines in other coverage). Erle I know does not want to commit to any one date for this transition, and I think we would both emphasize that there have been several step changes, often different in timing in different regions, in the relationship between human population and landuse and land transformation. These changes and landuse relationships need to be better-studied and better quantified. Archaeology, which I represent among the contributors on the PNAS paper, has a lot to contribute here. Archaeologists in a sense have been gathering such data without realizing its relevance to issues of long-term global change, and archaeologists are generally very region and period focused-- archaeologists, we might say, have their heads down holes-- with less awareness of the macro-scale and really long-term comparisons. I think that it is time for that to change, and I hope that more archaeologists will start see how their evidence can contribute to better models of long-term landuse and ecosystem management. It is time for archaeologists to become a bigger part of these discussions. 

We need to get some BIG ARCHAEOLOGY going. Then we can return to the issue of when the Anthropocene began.

Thursday 21 February 2013

Earlier sorghum in Sudan

I have recently been made aware of a small report in Nyame Akuma on Kasala (northeast Sudan), where Italian researchers have restarted research which can be regarded as following on from the 1980s survey headed by R. Fattovich. The new work has included the study of some plant impressions in ceramics published as "Sorghum exploitation at Kasala and its environs, North Eastern Sudan in the Second and First Millennium BC" by Alemseged Beldados and Lorenzo Constantini in Nyame Akuma vol. 75. As its title indicates this study does confirm the present of Sorghum bicolor, plausibly (but not definitively) domesticated, in ceramics from the site of Mahal Teglinos and some from near by survey collections. It reports examination of 25 sherds of which 11 from Teglinos and 11 from survey have sorghum.

As many will know I have been critical of some previous sorghum identification from impressions, in particular coming out the lab in Rome (most infamously those from Oman and Yemen). As a result, in various tallies of early sorghum I have always regarded the 1980s report of Sorghum of the Kasala region survey as requiring a big question mark next to it (e.g. "The economic basis of the Qustul splinter state"). The sorghum here, at least in fig 4, looks legitimate. The suggestion that grains shape (narrow versus wide) can be used to identify both wild and domesticated sorghum is more problematic. Meroitic Umm Nuri produced very very thin but apparently domesticated sorghum (published by me in Sudan and Nubia 2004).What is really needed is clean views of spikelet bases (for wild versus domesticated hulled forms) or evidence for still attached rachillae (especially in free-threshing forms).

I now believe that sorghum is there in Kasala, dated by ceramics (Mokram group) and association to 1500-500 BC. This is important news, as it takes sorghum earlier probably than any of the find in the Nile Valley, which are mainly Meroitic, and with possibly earlier Napatan sorghum at Kawa (in Sudan and Nubian 2004). This is a relief given that it is India before this time by at least a couple of centuries, and maybe more (for an updated review of early African crops in South Asia see by papers in Nicole Boivin, either that in J. World Prehistory on Arabia, or the Etudes Ocean Indien paper [in English]).

Some of the other identifications, notably cowpea (Vigna unguiculata) reported from one impression remain unconvincing, at least as photographed, and I really cannot except them on this sort of evidence. I would also expect pulse seeds to make poor temper for pottery. While we might expect this species in this region and period, as it was in cultivation prior to 1500 BC in West Africa and had arrived in India too by this time, I'll await more convincing evidence.

It is a pity high quality imaging, especially SEMs, were not made of the casts as, then one could see finer details of morphology like characteristic hairs, etc., that really clinch an ID. (See, for example the unicellular  e.g. w&v in the images from the Essouk archaeobotanical report, also a rachis stalk which suggests it is domesticated).

Also tantalizing is the evidence for millet, Setaria, impressions in 3 sherds. As illustrated, one could also propose a Bracharia and we really need better resolution SEMs and husk comparisons to get this to species level. Nevertheless it is plausibly a fit for S. sphaceleata, which is of particular interest as the  "lost" millet of Nubia,which we have evidence for cultivation of from Napatan to Medieval times (Kawa, Qasr Ibrim, Nauri). The origins and history of this lost millet of Nubia really needs to be chased down. It has gone extinct from Nubia in the past millennium, replaced by Setaria italica.

(Thanks to Mike Brass for bringing this paper to my attention)

Wednesday 20 February 2013

Unravelling agricultural packages

Two recent studies, one for the west and and one for the east, illustrate how crop packages unravel and become less diverse as they spread. The spread of agriculture is so often presented as a processing of unfolding, like a blanket being stretched from the point of origin outwards. This is especially true of the spread of Near Eastern agriculture, a truly diversified crop package of cereals (multiple kinds of wheat and barley, pulses, flax, plus livestock). But when the spread of agriculture is examined in detail, it is clear that crop species and varieties drop out along the way, and those which do make it probably become less genetically diverse. A recent database analysis of Neolithic Ireland illustrates the extreme western edge of Neolithic dispersal from western Asia. Published by Meriel McClatchie (whose PhD hails from here at UCL) and various collaborators (including UCL colleague, Sue Colledge), has been published in Journal of Archaeological Science, "Neolithic farming in north-western Europe: archaeobotanical evidence from Ireland" . This study demonstrates the clear pattern of quantitative reduction in most crops in Neolithic Ireland compared with elsewhere in Europe. Emmer wheat, virtually no einkorn (and one has to ask how securely identified any einkorn was), naked barley and a bit of flax-- that pretty much sums up Neolithic Ireland, in contrast to the 8 "founder crops" that are meant to characterize the start of agricultural dispersal from the Near East. 

A similar barley and wheat (with a dash of flax) characterizes the UK early Neolithic, which like Ireland see the dramatic introduction of cereal farming shortly after 4000 BC. As recently suggested in the study of radiocarbon dates from the UK (Stevens and Fuller in Antiquity, Sept 2012). One looks forward to further Irish Analyses to see whether the collapse of Neolithic cereal farming that Chris Stevens and I see in the England and Scotland cereal data also held true in Ireland.

This parallels what we see in the East, in India for example, which has recently been mapped in the paper I co-wrote with Nicole Boivin and Alison Crowther, "Old World Globalization and the Colombian Exchange: comparions and contrast." In South Asia wheats (including glume and free-threshing), barley, several pulses and flax, all seem to be important on the Indus Valley, but this package becomes less frequent and less stable as one moves into "inner" India. Sure enough wheat and barley make it both eastwards to Bihar and south to Karnataka, but generally with a strong preference for barley few or no pulses. In China only select wheat, and rarely barley, makes any showing at all, and there wheat is quantitatively negligible. This highlights that in some cases the caloric and subsistence needs are not likely to be served by the introduced cereals from the Near East. Some years ago I made the case (Antiquity 2005) that wheat and barley in Southern India might also have been status crops, used perhaps for beer, rather than as staples. One can ask the question as to what extent some the westernmost spread of cereals in Europe was as much about preferred foodstuffs rather than subsistence necessity when wild sources like hazelnuts were still so readily used and available?

There are broad similarities but also differences in the outward spread of crops from the Fertile Crescent. While in India and China this spread is seen largely in terms of the adoption of crops by local populations, in western Europe there is evidence for a greater role of migration. While in India we tend to attribute this to the local importance of other crops, Brachiaria ramosa and mungbean in the south or rice in the Ganges, that was clearly not the case in Ireland. So I wonder if we are seeing both the effects of crossing ecological frontiers, perhaps quicker than some crops can adapt, or beyond which some crops just can not adapt. Northern Europe certainly presented great challenges to agriculture, highlighted in its extreme margins such as Norway, but also in Britain by the apparent abandonment of cereals in the later Neolithic, perhaps as temperature retreated somewhat (Stevens and Fuller 2012). Monsoon Asia was not the most suited to the Near Eastern crops either, which also points towards social rather than caloric drivers in crop spread. In another parallel with distant Britain the agriculture and sedentism in parts of the Deccan, most clearly in western Maharashtra, where wheat and barley were quite prominent, appear to have collapsed and possible were abandoned over a wide area (in this case around 1200-1000 BC at the end of the Jorwe period).

Both of these studies show the importance of larger regional datasets, in which broad patterns are often visible even with simple quantification. This broad patterns raise questions that in turn call for more intensive sampling and local studies to work out wheat is actually happening at the periods of intial adoption or abandonment. What is missing currently is more usable data from the middle, Central Asia, the Iranian plateau, etc., so that archaeobotanical databases can become truly continental across all of Eurasia.