Post-Domestication regional evolution

Setaria italica grain variation:
above, from Gansu;
below, from Karnataka

It is true that evolution never stops--a suitable point to reflect upon on Darwin's birthday (12 Feb 1809) Some authors, would therefore insist, that domestication processes never cease and are always unfolding (a key argument in the recent book by Robert Spengler, Nature's Greatest Success), but I think there are grounds for differentiating the initial domestication episode that separates cultivars from the their wild population and later diversification and regional adaptation that took place within geographical subsets of a crop. In a paper in 2009, "The nature of selection during plant domestication", we drew attention to some differences and different expectations between domestication and diversification [incidentally that paper was also published in February 12, the 200th birthday or Charles Darwin]. The expectations are that diversification may occur over shorter timescales, differ between regions, and may (but may not) involve some conscious selection, based on farmer preferences. As archaeobotanical datasets have become larger and from more regions it offers the potential to compare and contrast how crops were evolving and differentiating across regions-- at least in those traits we can observe on archaeobotanical material. As noted in a recent blog (Bigger Beans...) there is clear evidence for selection for larger seeded legume crops around the greater Mediterranean some time after the classical period. While Grasso et al. (2025) argue for intentional selection in southern Italian farmers of the Middle Ages for larger broadbeans, I suggested in a previous blog that this might not be so because of the striking parallels across lentil, chickpea, grasspea and broadbean for macro-seeded forms around a wider Mediterranean world. This coincidence suggests to me an unconscious process of parallel evolution/adaptation to something in the ecology of bean farming in Late Antiquity to the Middle Ages (perhaps heavier tillage and also less incidence of water stress).

Aspects of grain size and grain shape are easily measured, and indeed have been measured for many years. Last year, in a large compilation of grain metrical data from archaeological assemblages acorss Eurasia, together with Rita Dal Martello, Robert Spengler and other colleagues from the Max Planck archaeobotany lab, we considered Contrasting diachronic regional trends in cereal grain evolution across Eurasia: a metadata analysis of linear morphometrics from the ninth millennium BCE to today. This study considered barley, free-threshing wheat (presumablty predominantly hexaploid bread wheat), and the millets of Chinese origin, Panicum miliaceum and Setaria italica. All four of these crops have pan Eurasain distributions, with dispersals beyond their regions of origin beginning in the Neolithic and having largely reached their maximum distributions by the end of the Bronze Age. As these crops came into a region one can expect them to adapt to local conditions, both ecological and cultural. What we found that is most striking, however,  is parallel trends in size/shape change in different crops in the same region, and often contrasting directions of change in different regions. While one might expect this with wheat and barley, that might be grown together in the same season, to find this across these cereals and millets is striking. The image above compares regional trends in grain length and width in free-threshing wheat, while the image below compares trends in the millets. Over the past 3000 years wheat and both millets tend to get longer in Central Asia; this is also true of both millets in East Asia. By contrast in northern Europe grains of all three species are becoming shorter over the same period. In Europe, wheats on average become shorter and fatter in north, but longer and skinner around the Mediterranean. In Central Asia wheat behaves more like southern Europe and the Near East. 

This all points to different selective environments in different regions. Sometimes shared across crops. Previously smaller scale, and shorter timeline studies have suggested that as wheat moved east to China grains became shorter and plumper (Liu Xinyi's "virtue of small grain size"), perhaps to make them more millet-like for cooking in East Asian boiling traditions. It is not clear such patterns hold up. Would such an explanation also be suitable for the trends in post-Roman northern European wheat? More problematic still is that the large dataset in Dal MArtello et al. (2025) is that decreasing grain length is seen in wheat starting in central Asia around the same time as its arrival in East Asia. These regions we might expect to have different cooking traditions and different cultural selection environments? The trend reverses around 2000 years ago with grains again getting larger.

An unambiguous explanation for this is elusive. It could be that there were some environmental factors in each region acting across crops. These need not be directly on grain size either, as grain size may scale allometrically with selection on other aspects of size, like plant height. Shorter and smaller plants might be more resistent to lodging in some kinds of weather or more drought tolerant. For example the Indian shot wheat, Triticum sphaeroccum,  has particularly short grains, as well as shorter plants, which seems to evolved twice in South Asia as adaptations to extremely high temperatures and evapotranspiration, even though sphaerococcoid grains reduce grain weight and overall yield (see Cheng et al. 2020).

The more general point is that crops have always been evolving and differ across regions. The foxtail millet (Setaria italica) grains at the head of this post contrast short plump grains from China (Lixian, Gansu) and skinner grains from India (Sanganakallu, Karnataka) both from the UCL archaeobotany reference collections. Explaining these differences may be hard, but what is clear that archaeobotany and systematic measurement of more assemblages can provide a window on tracking how regional populations varied across time.

Ancient DNA in charred grains? More bad news.

No one can have missed the massive impact that ancient DNA has been having on the history of human populations and those of several domesticated animals. Bones, at least some of them, provide a nice venue for the preservation of old genomes. Plants have featured much less in this story, with estimates of 200 C) for sometime (many hours)-- does not do DNA any favours. This who have worked on ancient DNA have tended to focus on desiccated plant remains- from dry desert contexts.

A  new report on ancient DNA extraction from archaeological grains (Lundstrom et al 2018), in this case barley, from Medieval and Late Medieval Sweden, reports some good success from some dry grains from a 17th century's Bishop's burial, some success from waterlogged specimens but no success from 46 charred grains. This replicates similar attempts to get aDNA out of charred Finish barley (Lempaiainen-Avci et al 2018) and methodological trail of Nistelberger et al. 2016 who tried High-Throughput Sequencing ("shotgun sequencing") on various charred archaeological grapes, maize, rice and barley (Pictured at right), including rice provided by my lab from India, Thailand and the Comores. Nistelberger et al. concluded that charred material is likely to rarely yield sufficient reliable genetic data, a conclusion re-iterated by two Scandinavian studies.

The open question is what does this entail for older aDNA results, using "old-fashioned" methods, i.e. targeted PCR, to extract chloroplast DNA, which appears to sometimes be quite successful in differentiating indica from japonica rice for example (Castillo et al 2016), or which was used in the early days of aDNA in the 1990s to separate tetraploid from hexaploid wheats (e.g. Allaby et al 1997). Estimates then were that maybe 5% of charred grains might have some aDNA in them, but maybe those were generous over-estimates? Are we now supposed to reject such earlier work and methods out of hand? Or does it mean that methodologically, there is something about current high-throughput methods that has not solved the problem of dealing with the highly fragmented and sparse DNA that is thought to be preserved in a minority of charred remains? Reading the fine print, Nistelberger did identify a small amount of ancient DNA reads, but they regarded them as so few as to be "inconsequential". But if little is all we are left with maybe we need to change our aims to make these consequential through the questions we ask of them?

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 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). 

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.

Predomestication cereal processing and storage

The latest Antiquity includes a detailed treatment by Willcox and Strodeur of Large-scale cereal processing before domestication during the tenth millennium cal BC in northern Syria at Jerf el Ahmar. The archaeobotany of Jerf has featured large in discussion in recent years on Near Eastern domestication, with apparent evidence for an early arable weed flora (see Willcox 2012 for latest), some grain size increase (reported in Willcox 2004, discussed further in Fuller 2007), but with wild-type shattering rachides, mostly of barley and rye. Jerf has been one of the major datasets contributing to a "slowing down" of domestication, from how fast we thought it was before, and of a "de-centring of the fertile crescent." So it is important to understand just how the archaeobotanical evidence fits with the archaeology on this site, and there are some important details to digest. In this paper the present some more details on the spatial patterning of finds, especially rye and barley in relation to crop-processing (mainly later stage dehusking and preparation for grinding), and argue for possible storage in the 'public' multi-room round building in the the site. There is also discussion of rodent dropping, mainly mice (Mus), which argues for on-site cereal stores, the key context for the evolution of commensal rodents.

Pre-axumite wheat and barley preference: isotopic evidence

I seem to have overlooked this last year, but was excited to see some stable isotope results, (published last year in J. Arch Science by D'Andrea et al), from northern Ethiopian pre-Axumite  and Proto-Axumite sites (i.e. 800-100 BC). This indicate a strong tendency in human bones towards predominantly (but not necessarily) exclusively C-3 plant diet, i.e. such crops as wheat and barley, but with limited C-4 input. This is of interest since Sorghum, tef and finger millet, all of which might expect to have been around are C-4 plants. So the mystery deepens as to the antiquity of these taxa in agriculture in this region-- or at least they were not very important. If memory serves there is some evidence for tef from around this period (but mainly later)-- treated in some detail by D'Andrea (and blogged previously), where as the earliest finds of finger millet and Sorghum are later and Axumite Also there is an important contrast with the domestic fauna, which have a distinctly different diet form the people. Cattle and donkey have a strongly C4 signature suggesting grazing or foddering mainly from the savannah grasslands. Sheep, goat and gazelle fall in between suggesting C4 grazing mixed with browsing of C3 shrubs etc.

Dating archaeobotanical treasure troves from Armenia and Peru

The arrival of a new issue of Antiquity is always a welcomed event. The issue that arrived in my mail box this week a particular trove of treasures of an archaeobotanical sort. Not so much for archaeobotanical reports as such (the only such is the study by Willcox and  Strodeur on the details of Jerf el Ahmar), but for tantalizing new information of sites that have exceptional plant assemblages, or that one expects will in the future, like the Han era Pompeii, Sanyanzhuang (blogged below). Two sites, which are well-known for exceptional preservation are the Areni-1 cave complex in Aremenia (Areshian et al in Antiquity), left, and Huaca Prieta mound in coastal peru, below right (Dillehay et al.). 

     Areni made the news a couple of years ago for its early leather footwear, from ca. 3500 BC (Pinhasi et al in PLOSone), but it also has dessicated plant remains of many sorts: emmer and free-threshing wheat and barley, of course, but also lentil, grasspea, grapes, plums, walnuts, almonds and pears. How many of these fruit and nuts represent species that were available wild in the region, were under cultivation or introduced as cultivars still needs to be clarified. The site has produced features indicating on-site wine production, so presumably grapes were cultivated, from at least, from around 4000 BC. 4000 BC is associated with the earliest material reported so far, but the site still has much to yield to excavation, presumably including earlier material. Late samples from the past 2000 years include cotton and textiles.

     Huaca Prieta also boasts exceptional archaeobotanical preservation, and with a long sequence it provides information that suggests the chronology of cultivar introductions in this region. Few plants are likely to be native here and so their introductions point earlier cultivation and domestication elsewhere. This includes Cucurbita sqaush, avocado and lima bean at 7000-5500 BC, and thereafter the appearance of chillis and bottlegourds. Cotton cultivation was established around 4800 BC, and after 4500 BC maize was added to the repertoire. This is some of the best dated and documented early maize in South America, detailed of which were published earlier this year (see previous blog). Peanut, sweet potato and quinoa also come from later levels. Full details are not yet published but some summary can be found in the on-line supplement. This site has also produced coca leaves, indicating the long traditions of chewing this drug plant. Dillehay and colleagues reported the earliest for use of this drug, back to ca. 6000 BC, from elsewhere in northern Peru about a year and half ago, also in Antiquity. Intriguingly this drug plant, plausibly from across the Andes, appeared to already have domestication features at this date.

Taking agriculture to the edge: Arctic Norway

We usually think about the spread of Neolithic agriculture as an inevitable, progressive march, as well-adapted cereal systems, for example Wheat and Barley from Near East, are extended along favoured soils and river valleys, for example along Europe's Danube. While this is our standard wave-of-advance model, and it may have much going for it for middle latitudes, we often pay less heed to the limits of agriculture, and past attempts to push those limits. A new study on the introduction of agriculture to northern Norway provides a nice example. Per  Sjögren and Johan E. Arntzen report in Vegetation History and archaeobotany the limited macro-remains evidence, pollen evidence and some settlement data on the earliest agriculture on Kveoy Island, at nearly 69 degrees North. Here agriculture was rather more marginal. There is doubtfully any agriculture before about 1000 BC, but then there is a Late Bronze Age establishment of fields. The seed record suggests mainly barley, but surprisingly a little bit of wheat (emmer?) also appears to be present. Like the Early Neolithic emmer in Britain (including Scotland), this tends to hint at some cold adapted landraces in early prehistory that we would be hard pressed to find in the relict emmer populations of today (in hot Mediterranean climates, Ethiopia, South India, etc.). This agriculture however may well have failed and there is a suggested hiatus in the last centuries BC/early AD, before a Late Roman Iron Age re-establishment of farming. This may be an extreme example, but I suspect as we look we will find more and more regions in which farming was given up, whether due to local climate swings or simply to choosing something less marginal.

Sourcing the 'lost Saraswati' river: new geological evidence

Recently published on-line in Geology  is a paper which might not appear on the surface to be very archaeobotanical, but which is important for thinking about the past agriculture of the Indus valley. This is by Clift et al (2012) on "U-Pb zircon dating evidnece for a Pleistocene Sarasvati River and capture of the Yamuna River". This paper provides sources for the headwater sediments in the various rivers of the Indus system based on zircon finger-printed (geological source dating in the 1000s of millions of years). These dated source profiles in turn are stratified in the Pleistocene and Holocene river sequences which have been dated by OSL. These river systems include the now extinct Ghaggar-Hakra river, often equated with the 'lost Saraswati" of Indian epic. The paper shows that while the Ghaggar-Hakra used to be much larger in the Pleistocene, drawing on the headwaters that now feed the  Yamuna, tha Yamuna had begun to flow  east into the Ganges before the End of the Pleistocene, and therefore well before the start of Harappan urban societies. Throughout the Holocene, including the Harappan period this river was fed only by seasonal monsoon rain in the east. This rain-fed Ghaggar-Hakra was  active until after 4.5 ka and was then covered by dunes before 1.4 ka. What this means is that the Ghaggar-Hakra, unlike any of the major Indus tributaries, was not fed by snow melt, which begins in Spring and may be unpredictable, but was entirely reliant on swelling its banks from the summer monsoon. This means it would have been an ideal river for winter crop agriculture, along the lines of the Nile flood regime which is keyed to the Blue Nile's monsoon source, with sowing of wheat and barley in Oct.-Nov. as the monsoon flood began to recede to leave behind a rich floodplain. These could then be left to mature until harvests in March or April, without fear of early snowmelt floods ruining crops. It really should come as no surprise then that so many Harappan Bronze Age sites concentrated in this valley. Nevertheless as monsoons gradually weakened (already underway during the Harappan period) with the flood water source retreating eastwards, and the Thar desert expanding, the valley became gradually drier and eventually choked with desert sands. This, however happened in Iron Age or post-Iorn Age times, so thus there is no basis for correlating any catastrophic shift in the Ghaggar-Hakra with the end of the Harappan civilization-- a notion which has often appealed to archaeologists.
[edited for typos 9.2.2102 DF]


For further discussion of the sedimentological results by geologist blogger: see here

De-centering the fertile crescent

The Near Eastern "fertile crescent" is the classic centre of origin for domesticated plants. Although when James Breasted coined the term (1906) he was thinking about the beginnings of agrarian civilizations in Egypt and Mesopotamia. The term become subsequently linked to Gordon Childe's notion (1935) of the "Neolithic Revolution" and with Vavilov's "centres of origin" idea, and the Fertile Crescent became, in archaeological argot, the centre of agricultural origins par excellence. In another classic paradigm-setting paper Jack Harlan used the Fertile Crescent as representative of a "centre" of origin, a focused area in which a package of crops was domesticated together, opposed to his notion of a "non-centre" of diffuse origins of crops that were not-packaged and spread out in domestications in space and time, of which the sub-Saharan savannah was perhaps the classic Harlanian exemplar. Within "centres" the Neolithic was meant to be a revolution, domestication rapid, and hunter-gatherers transformed to village farmers in one process. However, the evidence for this has been gradually unravelling for the Near East, with domestication-- the evolution of domestication syndrome traits in crops-- taking place quite slowly (3000-4000 years), and taking place not in a focused area, as a package of crops, but spread out and with as many dead-end proto-domesticates as paths into the crops and farming systems we know for later prehistory or history. In other words, there was no Neolithic Revolution as such but evolutionary processes, in the slow Darwinian sense, in which many incremental changes and transformations only added up to something revolutionary in retrospect, after millennia (some 150 to 200 human generations) of small steps.

You can find the case for this made in the December World Archaeology in my joint paper with George Willcox and Robin Allaby "Cultivation and domestication had multiple origins: arguments against the core area hypothesis for the origins  of agriculture in the Near East" which is a companion piece with our in press paper in the Journal of Experimental Botany  "Early agricultural pathways: moving outside the ‘core area’ hypothesis in Southwest Asia". Both are responses precipitated by publication late last year by Abbo et al. of a re-iteration of the "core area" view of  a tightly focused area where a single package of "founder crops" was domesticated rapidly. Such a view requires the assumption that archaeobotanical evidence is false fossil record, a poor reflection of actual domestication processes, i.e. that the gradual changes that appear in systematic archaeobotanical evidence, are somehow misleading or mistaken. I find this hard to accept-- perhaps because I am a practicing archaeobotanist and regard the preserved grains and rachises of prehistoric crops as our most material record of what these plants were like and how they were used in the past-- but also because recent years have seen increasing sampling and sample size and it is the increase in these data, and the detail with which they have been studied, that most points to the more gradual evolutionary processes. In addition, the "core area" view delimits a smaller number of founder crops and sets aside (or even rejects implicitly) the presence of past cultivars and domesticates now extinct, from the Abu Hureyra rye, 2-grained einkorn, the "new type" emmer ('striate emmeroid'), or the Gilgal oats-- all species which are the product of careful efforts of archaeobotanists to document the material remains of past crops and not to assume that all crops that ever were must still exist today. These constitute the "lost crops" of the Fertile Crescent just as much as Iva annua is a lost crop of the American midwest.  Coupled with the genetics of known crops that support multiple "domestication pathways" (such as in barley, emmer, pea, probably one-grained einkorn), the Fertile Crescent as a whole was host to something like 20 domestication "events," only a fraction of which can be localized in any one sub-area of the Fertile Crescent or can be expected to be present in modern germplasm collections. With this number of domestications and their diffuse nature across the Near East, the Fertile Crescent as a whole starts to look like a Harlanian "non-centre". On the level of individual crops and domestication events there may well be many centres of origins but in terms of regions it look increasingly like all were non-centres. The closer one looks for a core centre, the blurrier it becomes. 

Last year I declared in General Anthropology, a paradigm shift in agricultural origins research. Perhaps rather pretentious, but it remains the case that domestication appears to be a slower process as we gather more evidence, and there is evidence for more places of domestication around the world (North America, South India, separate North and South China, various parts of Africa, New Guinea, to name a few). This year I have put my money where my mouth is, and brought out a number of contributions looking at domestication processes in the Near East in particular and in comparison to the best documented crops from elsewhere (mainly in the Old World). This includes attempting to objectively calculate rates of domestication in terms of phenotypic units, the darwin and haldane, reported in terms of more general conclusions-- that domestication was slow and not somehow special compared to other forms of evolution-- in the journal Evolution (Purugganan and Fuller), and unpacked with more consideration of the variation across crops in the Near East and elsewhere in Vegetation History and Archaeobotany (Fuller, Asouti, Purugganan). See also the updated rachis data of Tanno and Willcox (2011)phenotypic change may differ in adjacent geographical contexts, and in particular that there appear to be in island effects on Cyprus, where grain size change was sped up (Lucas, Colledge, Simmons & Fuller). A careful consideration of the hard evidence, such as the essay assaying the southern Levant (Asouti & Fuller), shows that even for the Fertile Crescent we still lack the evidence we need to be clear about domestication processes in particular micro-regions, early cultivation or when agriculture emerged (keeping in mind that cultivation, domestication and agriculture are really different things from among the many transitions that gradually came together). We also note that there is alot more work to be done on the species that were important wild food stuffs, which were abandoned as cereal agriculture took off, the small-seeded grasses and legumes, wild nuts and nutlets-- evidence in other new archaeobotanical datasets such as that from Jordan (el-Hemmeh) of White et al. (which reports important evidence for how barley was harvested prior to domestication) or 3 sites from the northern and eastern Fertile Crescent (SE Turkey and Iran) of Riehl et al.. Of course as the role of many wild foods along side pre-domesticated cereals gains recognition, the difficulty of being clear what was a likely weed as opposed to gathered become acute-- an issue discussed in a short paper by Willcox on early weeds. Another recent paper out of London (Wollstonecroft, Hroudova, Hillman & Fuller on Bolboschoenus) illustrates an example of challenges that still confront archaeobotanical identification, and the the potential ecological and dietary implications of refining these to species level, in this case for the sedge Bolboschoenus glaucus.

 Most of these papers, now available on-line for a forthcoming Vegetation History and Archaeobotany issue on the Near East which will illustrate the revised (and more diverse) understanding of the precursors of Fertile Crescent agriculture: the tides seem to have turned on the simpler core area paradigm!

the trouble with two-row barley

I still seem to be playing blog catch-up, but I had to record something from a few months ago, which should be forcing us to think about the prehistory of barley in a whole new way. .. Palmer et al. of the Warwick molecular archaeobotany lab group of Robin Allaby published a major paper on plant ancient DNA in PLoSone this summer, "Archaeogenetic Evidence of Ancient Nubian Barley Evolution from Six to Two-Row Indicates Local Adaptation." On the one hand it has some nice clear ancient DNA results from the Nubian site of Qasr Ibrim, which allows these samples to be placed phylogenetically in relation to the gene the control whether barley is two-row or six-row. They have found what at first seems counter intuitive-- that all the barley samples have the six-row mutation, despite the fact that Nubian barley is usually regarded archaeologically as two-row, based on its symmetrical grains.

Cereal in Libya earlier than Egypt? New data from Huah Fteah

The spread of agriculture to Egypt presents a number of contrasts from that in Europe of east of the Fertile Crescent. For one thing it seems to be long delayed, with our conventional dates for the earliest cereal agriculture in Egypt, such as in the Fayum at 5000-4500 BC-- by contrast cereal agriculture is established in Greece and Pakistan by 7000 BC. What is more Near Eastern animal domesticates (sheep and goat) had reached Egypt at least 1000-1500 years earlier and spread rapidly through the Sahara. New data from Libya, rather than the Nile, suggests a new wrinkle in this story: cereal agriculture did spread earlier (by 6000 BC?), and probably was established in part of the Nile Delta, but made little headway up the Nile. How have I come to this conclusion?  [ed. June 2010: but see my own comment on the radiocarbon dates that have now overturned this]

In the latest issue of the journal Libyan Studies (vol. 40, 2009), there is a long preliminary report on the new Society for Libyan Studies/ Cambridge project at the famous Haua Fteah rock shelter, and thereabouts, the "The Cyrenaican Prehistory Projecy 2009" As part of this renewed work systematic archaeobotany is being carried out both at Haua and at nearby Hagfet al-Gama. Results from the macro-botanical work by Jacob Morales (normally based on the island of Gran Canaria) are presented over a few pages in Libyan Studies (pp. 83-88), and seem to be highly significant, if understated. Seeds are generally few and not surprisingly most are wild species. But of note is the the occurrence of barley grains and free-threshing tetraploid wheat (T. durum) rachis from the 2008 samples of Hagfet al-Gama. These are yet to be directly dated, but the cultural association is with the socalled Lybico-Capsian period, characterized by being non-ceramic and conventionally termed "Mesolithic". The Neolithic, in which older work identified domesticated sheep and goats along with ceramics, dates from ca. 5500 cal.BC-- based on the the latest radiocarbon dates. These finds from the Lybico-Capsian then suggest that domesticated cereals, deriving from the Near East, were already present somewhat earlier. Of course we must await more data, and direct dates; as well as results from new faunal analyses to see if any domestic fauna occurred alongside this pre-ceramic Libyan cereals... at present, however, we have tantalizing prospect of an earlier, hitherto undetected diffusion of cereals to northern (Mediterranean) Libyan, presumably over land via the Nile Delta-- where equivalent evidence is likely buried under meters of alluvium. Such a scenario makes the delayed diffusion of cereals into Middle or Upper Egypt and the Nile Valley all the more striking. In this region the 'Primary Pastoral Community' (sensu Wengrow) seems indeed to have been rather averse to cereal farming.

More genetic reviews on domestication

Domestication seems as hot a topic as ever, everyone is writing review papers on domestication, especially from a genetics perpsective. Often with varying degrees of ignoring, or sometimes misconveying the archaeological contribution. The paper by Brown et al in TREE late last year is a nice example of the integration of genetics and archaeology, with a focus on the Near East; there was also my own attempt (Purugganan & Fuller, in honour of Darwin). But here I would like to flag some others.

Writing recently in Plant Physiology, Sang Tao (who has done important work on finding and sequencing the sh4 domestication genes [Science 2006] which contributes to non shattering in domesticated rices-- and is shared across indica and japonica), reviews genes and mutations underlying domestication in grasses. It summarizes some of the recent functional genes reported and sequenced from rice, barley and wheat, with focus on thise genes involved in tough-rachis/ non-shattering. References to the archaeological record are absent. The general conclusion is that most domestication genes are a single mutation for a single trait, despite the fact that they are shared across diverse cultivated lines that may have different phylogenetic origins. He therefore conludes that hybridization and gene flow moved adaptive domestication genes across early cultivated populations. Indeed, this was probably a key factor in rice domestication. But contrary to Sang's assumption that non-shattering (sh4) arose in indica, I have argued (in a recent WA) it is likely to have arisen in japonica and spread to South Asia with japonica rice and other Chinese crops (and harvest knives) in the Late Harappan era (ca. 1900 BC), which represents something of a 'Chinese horizon' in northwestern South Asia.

There is a fundamental implication of a key role of hybridization in the formation of the crops we know today. Wheat researchers have long knwon this, due to polyploidy. Hexaploid bread did arise by hybridization, between a domesticated tetraploid and a wild relative. But genetics is increaaing suggesting this sort of thing was not the exception but the norm. Barley has tow distinct origins (West and East of the fertile crescent), but naked barleys of both origin share the mutation nud. The evidence indica rice clearly implicates hybridization in the making of fully domesticated indica: domestication genes that were selected by Neolithic Chinese farmers foufound their way through pollen into primitive prototype indica cultivars, which already had important adaptations to the monsoonal environment of South Asia.

This seems to raise a further question which is to what extent gene flow and hyrbdization was crucial in the earliest stages of pre-domestication cultivation? The move to accepting a protracted transition to domestication, would seem to open up this possiblility. Thus selection for large grains in one area, non-shattering in another, and erect growth in yet another seems plausible, and the extended period of pre-domestication cultivation may be necessary for this various adaptation to be brought together. Culturally this implies contact, the exchange and sharing seed stocks between communities, and in the case of rice apparently over long distances. For archaeologists who have studies things like the trade in obsidian, or the translocation of crops between African and India, in prehistory, this should come as no surprise. People were connected (even if irregularly and indirectly) over quite long distances sometimes. The evolution of cultivation systems and the crops in them was taking place in the context of interconnected communities and cultures.

Sang also raises but does not attempt the solve the historical problem that temperate japonica rices have another additional non-shattering gene (qsh1), which seems to me to be most likely selected for later as japonica cultivars were subjected to new forms of harvesting (such as basal harvesting by true sickles, which occur in China from the late 4th/ early third M. BC?) and processing.

Large granaries and pre-domestication cultivation

Pre-domestication granaries in Jordan: Kuijt & Finlayson (2009) in PNAS report preserved archaeological structures for granaries—round buildings which would have had raised wooden floors and lifespans of ca. 50 years. (This has also been reported by Michael Balter on the ScienceNOW blog.) They suggest these structures might have contained morphologically wild barley. It is a pity the archaeobotanical evidence from this site, which they elude to, is not actually presented in any detail (nor is whoever has done the work mentioned in the acknowledgements).

The quality of the excavation and the reconstruction of the architectural remains is exemplary, and leaves little doubt that raised floor granaries were constructed at Dhra (and presumable other Southern Levant sites) in the PPNA, by ca. 9200 BC. This is important evidence, since storage has more often been inferred than structurally demonstrated. They associate these structures with evidence from other sites for morphologically wild cereals (Gilgal: oats and barley; Netiv Hagdud: barley) and suggest that large-scale storage was a key part of the transition to reliance on pre-domestication cultivation. This evidence for large scale storage starting only in the PPNA seems to challenge our expectations that storage amongst hunter-gatherers ought to be a prerequisite for cultivation. Instead it appears that large-scale storage occurs alongside, or even results from (occurring after), the move to early cultivation. Undoubtedly there would have been smaller-scale precursors, such as the more limited evidence of possible Natufian silos and caching that they review.

Also of interest is the observation that storage structures move from public spaces to the inside of houses at ca. 8500 BC in the PPNB and then to special rooms by 7500 BC. This shift seems to parallel the move from early pre-domestication cultivation to more intensive cultivation as domestication traits, like non-shattering that began to increase in cereal populations from c.8500 BC and became predominant after 7500 BC (as documented for the northern Levant by Tanno & Willcox, Science 2006; and for the broader region, including Jordan, in Fuller 2007 Ann. Bot.—most of the evidence from Jordan is from S. Colledge (2001) Plant exploitation on epipalaeolithic and early neolithic sites in the Levant, BAR). This also parallels a trend in the find spots of food processing tools (grinding stones), documented by Karen Wright (UCL), which move from public spaces in the Natufian to inside houses in the PPNA-Ea. PPNB and into well-hidden back rooms by the end of the PPNB (Wright, K, 2000. The social origins of cooking and dining in early villages of western Asia, Proceedings of the Prehistoric Society 66, 89-12)

There is something of a southern Levant bias reflected in this paper, as archaeobotanical evidence for cultivation, and even archaeological evidence for possible storage structures from the Northern Levant (Syria) seems to be ignored. As reflected especially by the work of Willcox (e.g. Science 2006; the Balter News Focus piece of 2007), as well as work by Hillman and Colledge, pre-domestication cultivation is demonstrated earlier by ca. 10,000 BC at Mureybit and Qaramel. Perhaps upto 500-1000 years earlier at Abu Hureryra. Many northern sites (Mureybit, Tell Abr, Jerf el Ahmar) have large sunken floor ‘public buildings’. While these are usually regarded as structures of ritual use, they may also have been used for storing grain as suggested recently by Willcox et al. (2008) based on grain finds at Tell Abr., Vegetation History & Archaeobotany 17, p. 315). Oddly, this paper’s weakness is that it has a rather limited view of the archaeobotanical evidence, ignoring the broader macro-regional pattern for the shift to cultivation that accompanies increasing sedentism and architectural investment (both in the northern Levant/upper Euphrates area—probably first, and then the Jordan valley, a little later). It ignores archaeobotanical data from elsewhere in Jordan (e.g. publications by S. Colledge, J. Meadows). The examples it draws on are some of the least well-documented cases for pre-domestication cultivation, as they lack arable weed flora or sequences of change towards morphological domestication (by contrast to northern Levant cases), and despite some headline pieces in Science have never been published in any detail. (I nevertheless agree that they almost certainly are pre-domestication cultivation). In the end this is a nice archaeological find, with some great illustrations, but if feels somehow that they rushed to press without too much account for the archaeobotany.