Saturday, 9 December 2017

Buckwheat origins remain elusive

Harriet Hunt and colleagues have provided a new critical assessment of data and potential data on origins of the buckwheats (Fagopyrum esculentum and F. tartaricum) in a Vegetation History and Archaeobotany article. Buckwheat is an important carbohydrate crop at high elevations in Asia, as well as parts of Japan and Europe, but it has remained quite elusive archaeobotanically.

It is absent from the many large charred seed assemblages in central China, or the charred and Fagopyrum identifications as distinct from many other Polygonaceae. Even if we accept all identifications of Fagopyrum, there are several wild taxa in this genus that will have nothing to do with the cultivtion of the crop. They consider how reliable stratigraphic dating controls are for many of pollen sequences, but even so, pollen never allows for the direct dating nor direct association with human activities that archaeobotany does.
waterlogged assemblages of the Lower Yangtze. In the Indian Himalayas where it is traditionally an important crop, finds have been few, restricted to later First Millennium BC and medieval finds in Nepal. The new review by Hunt et al has compiled evidence from archaeobotanical macro-remains, a few reported based on apparent archaeological starch remains, and the many more reports from pollen diagrams. They take a threshold of fairly high quantities in pollen diagrams, but less clear is whether one can always rely on

Distribution of wild Fagopyrum species (Campbell 1997, IPGRI)
One of their key conclusions is that the past distribution of wild Fagopyrum species, including the wild progenitor of F. esculentum, was more widespread. Extending further north, even to the north of Sichuan. This certainly seems plausible and could support a domestication in Sichuan north of where modern wild populations (in NW Yunnan) have tended to suggest domestication. They point to a few pollen cores from Shaanxi and Gansu apparently 5000 years old or more, as perhaps relating to early cultivation-- although the absence of grain finds in these regions which have had considerable archaeobotanical sampling in recent years surely calls into question the paper's tentative conclusion that cultivation had begun before 5000 BP.  Another problem with many of these pollen cores is the reliability of dating. For example, the pollen sequence at Xishanping, which was collected through an archaeological sequence, has a number of inverted radiocarbon dates, suggesting reworked residual materials, but the short (and old) chronology followed by Hunt et al. removes the out of sequence dates-- which would make sense if this were a lake core with constant sedimentation, rather than a sequence 5 varied archaeological layers. A safer, and archaeologically logical reading of the original stratigraphy (see raw data in Li et al 2007) date makes the buckwheat pollen occurrence only slightly older than 3000 BP. (The short chronology also implies that wheat was present at this Gansu site before 2600 BC, which does not fit with the accumulated evidence on wheat's arrival in Gansu (as noted already in a previous blog), especially AMS dates (see Stevens et al 2006).

A more critical reading of the dates in the sequence of the earlier pollen cores find little support for any substantial quantities of Fagopyrum pollen before around 4000 years ago, so I stand by previous inferences of domestication taking place around this period. Nevertheless from the Second Millennium BC onwards, some archaeological seeds of Fagopyrum, possible supported by starch finds points to cultivation of this crop, with a focus on west Central China and southwest China, consistent with early dispersal around the eastern front of the Tibetan plateau. Nevertheless with central and eastern China, the lower reaches of the Yellow and Yangtze basins buckwheat appears to have been absent, from macro-remains (and supported by early Chinese written sources). In this regard some of the apparent pollen reports from natural cores in the Lower Yangtze seem unlikely to represent cultivation. Despite being clearly present among the crops known in early Tibetan languages (and many related Burmic languages), and having likely been loaned from a Tibetan language into Chinese since the Han dynasty period (see Bradley 2011), buckwheat remains elusive in Asian archaeology.

This new paper by Hunt et al. provides a solid starting point for new research on buckwheat origins, with a thorough compilation of pollen and archaeobotanical evidence (in China)long with some critical thinking on the rather limited genetic data.

Friday, 8 December 2017

Neolithic wine drinkers in Georgia or wishful thinking

Strong inference I was always taught comes from thinking through multiple working hypotheses and assessing which hypothesis is best supported by available evidence and trying to falsify alternatives. It is unfortunate if the quest for headlines and high profile publication gets in the way of clear thinking and an scientific approach. Of course sometimes evidence and conclusions are only partly certain, but when that is the case it should not be carefully hidden in online supplementary text and onreference claims of background fact as is the case in this study. I have to conclude weak inference reigns in the recent headline grabbing claim that the first grape wine makers anddrinkers were to be found in the Neolithic Georgia. While McGovern et al present a compelling read in their PNAS paper, and some apparently very technical scientific support, their presentation seems to me aimed to grab headlines and appeal to journalist or generalist and not really to convince scientifically the specialist. The fine print in the supplement raises many unanswered questions that undermine their conclusion. The failure to reject alternative plausible hypotheses for their result, the lack of reference to scientific names, regional flora inventories or vegetation surveys, as these would so clearly support alternative hypotheses…

Here is the claim: some interesting liquid storage vessels that could well be for wine storage have produced tartaric acid residues. This would indeed constitute part of an evidential base to argue for early wine, but on its own this is necessary but not sufficient evidence for the claim. Tartaric acid occurs as background in the soil—thus one learns in the supplement that some 11 sherds were rejected as having levels not sufficiently above background soil levels. What is more tartaric acid occurs in many fruits, not only grapes. Oddly they reject other sources with a flippant line in their supplement, “Other plants with high tartaric acid–e.g., hawthorn fruit and star fruit from east Asia, tamarind from the Indian sub-continent, and yellow plum from the New World—can be ruled out”- notable for being without any Latin names, without any citation of botanical sources on  these taxa, their chemistry, or on the regional flora from which to based claims about their distribution. What is worrying here is the inclusion of hawthorns (Crataegus spp.), and plums in this list. They claim that “yellow plum” is exclusively American—and while this is ture if what they mean is the species Prunus americana, but the broader Prunus genus, including numerous Cerasus cherries and Padus bird cherries, has high endemic diversity in the Caucusus regions, as well as numerous Crataegus species. There are ~70 species of Prunus native to Eurasia: are we really to believe that none contains tartaric acid in contrast their common American cousin? If so, how have these been excluded. Contrary to the dismissive statement in the supplement there are half a dozen Crataegus reported form the Caucasus region in the old Flora of the USSR, and several more to the South or to the north in Ukraine! (Flora of the USSR Vol. IX. Rosales and Sarraceniales, by Botisova et al 1939, English Language 1971 from Jerusalem, online here)

Grape pip with measurements (from
Bouby & al 2013 PLOSone
One might support an argument for grape wine production on archaeobotanical grounds if flotation samples were rife with grape pips and no other fruits, but in fact we learn that all AMS dates run grape pips turn out to be intrusive, Bronze Age and later. This does not support major use of grapes for wine in the Neolithic but quite the opposite! For Neolithic grape finds one must go to the Fertile Crescent, or indeed to parts of Mediterranean Europe, like Greece or Italy! While some of the co-authors have have done some cutting age work on the geometric morphometrics on grapes, e.g. Laurent Bouby, whose work on archaeological grape diversity in France is indeed cutting edge (e.g. the Vegetation History and Archaeobotany paper by Bacilieri, Bouby et al earlier this year), the deployment of these techniques on Georgian grapes from the Bronze Age and later (based on direct dates) does little to support a sequence of grape domestication in the Neolithic Caucausus.

Some sort of fermented fruit wine—the conclusion is plausible. But grape wine? That still seems wishful thinking. At best the sloppy and journalistic presentation of the evidence might be attributed to weak editing and inadequate peer reviewing combined with authors’ excitement, but at worst it represents obfuscation of the science to claim headlines and citations indices.

Thursday, 23 November 2017

The earliest wheats of Ukraine (5400 BC)

The eastern areas of Europe and their transition to the steppe that lead to Central Asia remains one of the less well-studied regions archaeobotanically. The sparseness of reliable evidence has meant that the region is sometime discussed in terms of an alternative eastern source of crops from Europe, in addition to the main thrust from Anatolia through Greece and the Balkans, and it is sometimes mooted as a region of some crop origins, such as spelt wheat. New data is always welcome, especially of a high empirical calibre, from systematic sampling and backed up by AMS dating.

New data from the Ratniv-2 site in Western Ukraine, near the eastern frontiers of the Linear Pottery (LBK) culture, has been published by Motuzaite Matuzeviciute and Telizhenko in Archaeologia Lituana. This is an important record of early crops, and as the authors point out, it clearly points to similarities to the West and Southwest in Neolithic  Europe and suggest a spread towards Ukraine from the West in the Neolithic, rather than the east. The assemblage consists of wheats, barley, flax, lentil and pea. Two direct AMS radiocarbon dates on emmer wheat grains place these assemblages between 5400 and 5200 cal.BC. Of particular interest is that the wheats here include not just einkorn and emmer but apparently at some of the socalled "new type glume wheat," which these and other authors sometimes equate with Triticum timopheevi, and 20th century relict wheat found north of the Caucasus (western Georgia). That the archaeological "new type" has the AAGG genome of timopheevi remains unproven-- although I agree it is likely. It is perhaps more accurate to regard T. timopheevi as the relict remnant of what was a once a much more diverse and widespread species of wheat, which in all likelihood originated in the Anatolia and spread through many part of Europe and east through northern Iran in the Neolithic. I have sometimes offered the name "striate emmeroid" as a descriptive alternative to  "new type", as it is hard to think of something that has been largely extinct since the Bronze Age as new, and this wheat type has been in discussion by archaeobotanists for around 20 years...

In any case, what is notable about this assemblage is that is corresponds to those crops that are most common in the Neolithic of southwest Europe, supporting the ceramic and settlement evidence that attributes to the origins of agriculture in western Ukraine to spread from the west.

The lost rice of South America

One of my pet interests is lost crops, or largely forgotten ones-- species that were important in the past which are either completely lost from cultivation today or very nearly so. They serve to remind us that the ethnographic present does not provide a full range of potential economic activities nor the full range of crops. They demonstrate that archaeobotanical evidence can provide important broadening of our list of potential crops to consider in future breeding and sustainability efforts. An endemic rice of South America can now be added to the list of lost crops.

This exciting find, that received quite a bit of media attention (e.g. in Science) was the recent report of a rice that was apparently undergoing morphological change, i.e. domestication. The archaeobotanical evidence, published in Nature Ecology and Evolution last month by Hilbert, Iriarte and colleagues as part of the ERC Pre-Colombian Amazon Scale Transformations project, comes 

from  phytolith anaylses through a stratigraphic sequence at the site of Monte Castelo in southwest Amazonia, dating to between 5300 BP and 700 BP, which includes rice husk phytoliths (the double-peaked cells) and bulliform throughout. The proportion of rice increased somewhat in the past 4000 years, but shifted especially towards a much higher ratio of husk types to bulliforms, suggesting the concerntration of husk phytoliths that one might expect from dehusking or harvested rice spikelets. It is at this stage that the shape of the husk phytoiths also starts to change, with phytoliths getting wider, taller and with more pronounced peaks. These are the kinds of changes that may be indicative of a domestication process and be a proxy for increasing grain size. The change takes places somewhere in the upper levels of the site, which are unfortunately not well constrained in dating, except being younger than 4000 BP and up to 700 BP or so. This suggests that the inferred domestication process took place or was even ongoing upto shortly before Colombian arrival from Europe and Amazonian population decimation.

One can quibble over whether changes in husk and inferred grain size increases must be human caused. The classic case of such a change in Chinese rice is decidedly NOT about domestication, as it takes place in sites South of Yangtze at the transition from the LGM to much warmer conditions, i.e. around 18,000-16,000 years ago. A full 10,000 years before the appearance on non-shattering rice spikelet bases appear-- domesticated by definition. When originally published by Zhao (1998 Antiquity) this was mistakenly dated to the Holocene, and thus inferred to represent domestication, but this falled a false equations (domestication because change is start of Holocene; start of Holocene because advent of ceramics could not possibly be any earlier). We now know the advent of ceramics transition in China took place around 18,000 years ago at Yuchanyan and possibly even earlier at Xianrendong, as already discussed for at least 7 years (e.g. Fuller et al. 2010). while domesticate rice, i.e. that was dependent on humans for dispersal, evolved during the middle Holocene, with the earliest large assemblage of non-shattering spikelet bases at Baligang by ca. 6500 BC and predominance in the Lower Yangtze as late as ca. 4000 BC (for a updated summary see here). It now appears most likley that the morphological change in husk phytoliths in South China was driven by the rapid climate change and especially the increase in carbondioxide which has major repercussions on plant productivity and morphology (see experimental work by Cunniff et al 2010), and thus the near doubling of carbondioxide that took place in the millennia just after the LGM (along with increasing temperature) ought to have hade major effects on rice productivity and aspects of morphology).

However, in the past 4000 years it seems unlikely that there were any climate or carbon dioxide shifts on quite the necessary scale, which makes the inference of a local rice domestication process much more likely.  A shift in grain size, however, would be expected to be accompanied by some selection for reduced shattering-- as this co-evolves in all of our better documented cereal domestications, most notably in Asian rice. Thus good flotation samples, with the required fine mesh of ca. 250 or 300 microns, ought to produce small charred rice spikelet bases. Recent experience suggests that everywhere we look, and do the requisite flotation, in tropical Asia, we find now that rice spikelet bases greatly outnumber charred grains and this tells us that they survive well and are archaeobotanically recoverable. This is also true to the major rice growing areas along the ancient Niger river. Some macro-remains would seem the obvious next step to pinning down more details about the evolution of this lost rice of South America. It would be highly unexpected if selection for larger grains did not take place alongside increases of indehiscent spikelet bases, as these co-evolve in other well documented cereals (as illustrated in a PNAS 2014 article).

It is also highly likely that increase in grain size implies management of soils, i.e. some sort of cultivation. This is contrary to the novel, but rather unconvincing, hypothesis of the authors that grains would have been encased in clay and dropped into the water. They cite as an ethnographic parallel systems of reseeding American wild rice (Zizania palustris) stands in the Great Lakes region of North America. But in that context there is no evidence for prehistoric grain size increase or domestication processes.The rice represented at Monte Castelo was likely a productive annual, as the authors note, and could have been encouraged by burning of competing vegetation after seeds are shed, in which case selection for seed size increase can be expected from the levelled playing field conditions of freshly cleaned fields which put a premium on rapid seedling establishment against competition from conspecific seedlings. 

South America boasts 4 indigenous wild rice species, Oryza alta, O. latifolia, O. grandiglumis, and O. glumaepatula, and only the last has annual ecotypes. South America's O. glumaepatula is also an AA genome, like domesticated Oryza sativa or Oryza glaberrima, and thus this suggests something inherently attractive for, or conducive to, domestication in the AA wild rices. Like Oryza species everywhere these are water-loving grasses, but there are still two ends of a spectrum from perennials in deeper water and annuals and places that are seasonally dry. Oryza alta, which can form mats along river margins, is a perennial (see, for example the photo at left lifted from Duncan Vaughan's 1994 monograph on the wild rices). Annual Oryza are prolific seasonal grain producers, and thus lent themselves easily to forager intensification, and it was such annuals that were ancestral of the early cultivars of Asian indica and aus rices, or African glaberimma (from wild annual O. barthii). By contrast perennial rices are less prolific grain producers due to investment in perennating stems, roots and more leaves. Thus Asian rices when available ought perhaps be expected to be used resources. The other continent with annual AA genome wild rices in Australia, where these are found in the northern parts. Lets see some archaeobotanical work carried out there, in the region of Oryza meridionalis, as one might expect parallel evolution for utilization and even management there.

Tuesday, 21 November 2017

Using big machines to look at the finer aspects of seeds

This year has seen three studies on high resolution x-ray computed tomography applied to archaeobotany, one using ct-scanning to recovered chaff hidden in ceramics (see Finding Rice Domestication in Clay), and two using a synchrotron to peer inside seeds, including soybeans and horsegram. past summer, I published with colleague Charlene Murphy, a Scientific Reports article on domestication of the Indian crop horsegram. While this article represents an important contribution on the domestication history of a major crop in India, and evidence for evolution of morphological change during that crops domestication in South India (see also our GRCE paper, reviewing all that is known about horsegram origins), this is really more significant for the methodological contribution to the archaeobotanical documentation of domestication. We were able to put our small archaeological seeds in a very large machine, the Diamond Light synchrotron (shown at left). which allowed us to non-destructively capture the the internal structure of the entire seed (not as straightfoward as it sounds as it takes a lot of computing time). And from this we could measure seed coat thickness on any of the 1000s of cross-section slices through our seeds (like that below/right)
horsegramOne of the well-known domestication syndrome traits in pulses is the thinning of the seed coat, tied to loss of germination inhibition. But it has been difficult to document this archaeologically. Seed coats are often destroyed in charring, but even if preserved they study on charred seeds would require destructive breaking of seeds. And even if damaged, it might only be possible to document the seed coat thickness in one or two places with an SEM or high powered normal microscope. As a result this has been rarely documented, which has lead to a fair degree of speculation on the evolution of thin-seedcoat, readily germinating pulses, as the result of conscious selection of the readymade mutants in the wild (although none have been documented in the present day)-- the domestication before cultivation hypothesis applied to lentils-- or positing a rapid conscious selection by those who initiated cultivation-- lets call this the pea breeding before agriculture hypothesis. The truth appears to be, however, a gradual evolutionary process as seed coats thinned over time, much like the evolution of increasing seed size or the non-shattering in cereals-- at least in horsegram. This can be seen in the chart below showing the thinning seed coat along side a trend in seed size increase in horsegram. Further work is needed on additional pulses to see if this pans out as typical of the pulses domestication processes, or whether there was variation, or indeed any cases of plucking domesticated types from the wild-- of which I am doubtful. At least now we have a method for approaching this.
This is actually, quite logical: established stands of pulses could be maintained and wild-type dormant seeds would constitute an established seed, and would recurrently add new plants to the the stand over a series of years. But due to annual human harvests mutations that reduced dormancy would get selected, and would be particularly important for any new populations planted in areas without existing wild populations. In this context we can expect the gradual evolution for thinner coated, more easily germinating seeds through selection across what are presumably multiple loci, as is evident in our archaeological horsegram data (shown left).

Soybean oil content in charred seeds?
The claim for earliest use of a synchrotron to look at charred archaeological pulse seeds, however, goes to our colleagues in China, in collaboration with Prof. Gary Carwford, Shandong archaeobotanist Xuexiang Chen. They argue that soybean underwent selection for increased oil content in prehistory during domestication-- undoubtedly true-- and that this can be tracked archaeological through a change in the number and size of pores visible on the inside of charred soybeans viewed through the synchrotron and High-Resolution Computed Tomography. I remain unconvinced on this last point, and although the paper reports on examination of modern soybeans and, other oily crop seeds, and experimentally charred seeds none of these are illustrated or really described so as to support this interpretation. The authors infer that more small pore is a product of more oil whereas large pores represent burned out protein, but is this true. The differences look to me more like artefacts of carbonization processes, and not a good proxy for the internal anatomy of the original uncharred soybeans. As the few illustrated example suggest larger and irregular pore are present in seeds with more distorted external surface anatomy (e.g. c), whereas small pores are more evident in better preserved examples (e.g. f).

Unfortunately, the central claim in this paper does not really add up, or at least are not well justified and explained in the text. This makes me very nervous about accepting the main conclusion of the paper, i.e. that the authors have demonstrated an increase in oil content in soybean during domestication by measuring the quantity of bubbles (voids) of different sizes in charred archaeological soybeans. Small voids are attributed to oil content and large voids to protein—but this is never demonstrated (for example in modern and experimental charred examples) or backed up by citations on soybean anatomy, as to why these voids should differ between oil and protein. That soybeans are oily, in contrast to most pulses is clear, but this also has major implications for the nature of archaeological finds. Most carbonized archaeological soybean are poorly preserved, distorted, full of large voids and small voids and very shiny on their interior. This is contrast to pretty much every other pulse I have seen archaeobotanically, from Vigna spp. to lentils and peas to Lablab. Even in the Chinese samples, presumably subjected to similar formation processes Vigna angularis seed present typical features of carbonized pulses, including a dense charred matrix with distinct cotyledons. In Glycine cotyledons are rarely evident and their interiors are heavily distorted by voids and bubbles. The obvious deduction is that this state of things is the result of the oil content in soybeans, and of course many other oily seeds, from cotton to sesame, also tend to show similar levels of bubbling and porosity when charred. If large voids in soybean are due to protein burning up during carbonization then surely one would expect to see this in any pulse, all of which have at least 20% protein content. It is true that the oil in soybean is contained in fresh seeds in many small droplets/sacs but upon charring things are likely to end up being very different. Oils are going to burn to more readily to gas than carbohydrates or proteins and thus create more bubbles and explosions of expanding gas. As this progresses and cracks to the outside of the seed allow penetration of gas (and some oxygen) from the exterior, one would expect this to speed up. The persistence of small voids then might be predicted to be the result of less oxidation, less temperature and perhaps other variables of charring conditions of a given seed. Cracking and penetration of gases into the charring seed may indeed be affected by aspects of domestication—thinning of seed coat, increase in seed size. Indeed, larger seeds seem likey to leave larger parts of their interior cotyledons unexposed to exterior cracks and oxygen; and in this context would be expected to preserved more small oil bubbles as a side effect of seed volume increase: i.e. the difference over time would reflect preservation artefacts rather than selection for genetic change. It is hard to see how at this stage we can deduce difference in underlying phenotype and genetics from this sort of data—at least until we have much better grasp on who charring conditions affect the distribution of seed contents, and this calls for some systematic experiments.
Undoubtedly soybeans were selected for oil content, but when and how this took place in relation to other domestication traits remains sadly unclear. I find I have to reject to conclusions of Zong et al., although their paper doe illustrate the potential analytical power of using a synchrotron to peer inside archaeological seeds

Sunday, 29 October 2017

Finding rice domestication in clay (new methods in archaeobotany)

One of the more exciting methodological developments in archaeobotany I have seen lately is the use of ct-scanning to look into chaff tempered ceramics and to extract in virtual terms the invisible plant remains therein. Aleese Baron, Tim Denham working with a range of colleagues have applied ct-scanning and computed tomography to produce images of rice chaff and rice spikelet bases from Neolithic sherds from three Neolithic sites in Vietnam published in Nature's Scientific Reports.
The sites are An Son, Loc Giang and Rach Nui. In all cases, conventional archaeobotanical evidence through macro-remains has been limited, although rice and millet as well as various wild taxa were reported from flotation at Rach Nui earlier this year. This makes the potential to recover plant remains from ceramic tempering quite tempting as an additional source of evidence on past plant use. As demonstrated by new evidence on sorghum domestication found in old sherds. However, while traditional we may cast impressions of those remains that are haphazardly represented on the surface, ct scanning allows full three-dimensional voids to be recovered from the interior of the ceramic fabric.
While patience and skill required to get such images is impressive, the results are breath-taking, with images of domesticated type, non-shattering rice spikelet bases pretty much as good as those found through flotation emerging (see left). It is not any surprise that these Neolithic folks in Vietnam were already dehusking fully domesticated rice and using the chaff to temper their ceramics-- this very much fits current hypotheses for the spread of fully domesticated rice into mainland southeast Asia from the end the Third Millennium BC (e.g. the recent review by Castillo in the journal Man in India). Methodologically, however, opens up the possibility for studying old ceramic collections from sites that may no longer be amenable to sampling through flotation or which lack good stratigraphy, at least so long as some ceramics are chaff tempered. This could prove quite useful for any earlier, less sedentary phases in the spread of rice, just as sherd impressions have proved so useful in Africa, right across the Sahara and sub-Sahara. Studying sherd impressions just got powerful new tool.

Thursday, 26 October 2017

Earlier Sorghum in Sudan (2017)

A few years ago I posted a blog on Earlier sorghum in Sudan highlighting the work by Alemseged Beldados and Constatini on sherd impressions from Kasala from the early Second Millennium BC. At the time I raised the question as to whether or not these impressions were wild or domesticasted. At the time I bemoaned the lack of SEMs and attention to spikelet base remains. That blog post attracted the attention of Frank Winchell (see his comments at the time), and around the same time Frank had met Michael Brass, then a PhD student at UCL. Through these interactions, online and eventually in person, we started a collaboration to re-examine ceramics that Frank has collected and studied from a site of Kasm el Girba 23, to the southwest of Kasala, from field work over 30 years ago. Frank has long been impressed by the present of a large number of apparently seed or chaff tempered ceramics in a ware type called Kharadag Plain, and through extensive examination in the UCL archaeobotany laboratory, casting impressions and SEM study, as well as re-assessing our reference material of domesticated and wild sorghum.

The results are highly significant, and have now been published in Current Anthropology. Domesticated sorghum morphologies were present much earlier than previously found, i.e before 3000 BC, more than a millennium earlier than the Kasala finds or finds in India. In addition the material represents a mix of almost equal parts morphologically wild (smooth spikelet base) and domesticated (torn rachilla). This suggests that the Kasm el Girba material is around midway in the domestication process, and by analogy with the protracted domestication now well documented for rice, wheat and barley, we should be considering this as an advanced stage of pre-domestication cultivation, and seeking the beginnings of pre-domestication cultivation sometime before 4000 BC. This has received some science journalism attention from Nature and Science News.

One of the other highly significant patterns is the Kasm el Girba faunal evidence, as previously published by Joris Peters: it represents a wild hunted savanna fauna. It lacks the evidence for sheep, goat or cattle, in contrast to the evidence for some pastoral component to the economies of the Neolithic around Khartoum from the Fifth Millennium BC at least. This calls into questions the widely accepted notion of "cattle before crops" in Africa (as per Marhsall and Hildebrand 2002). Certainly pastoralism gets established in parts of the Sahara around 6000 BC, long before any evidence for cultivation. It is also true that the earliest evidence for domestication of pearl millet, reported by Manning et al (2011), occurs alongside evidence for cattle and caprine pastoralism. But in this case we seem to see evidence for cultivation of early sorghum and sorghum domestication taking place among fairly sedentary hunter-gatherers and not their Sahelian pastoralist neighbours. This raises some exciting questions for further research in Sudan, and calls for renewed efforts in zooarchaeology and archaeobotany of the Early to Middle Holocene in northern Sudan, etc.