The drug before the calorie? Some hazy thinking on Cannabis domestication

Many have been excited this week about headlines claiming marijuana (Cannabis) was domestication in China 12,000 years (making it the first crop in East Asia). As the reputable journal Nature put it "pot farming first blossomed" in China 12,000 years ago. But was it so? How clear or otherwise in the evidence? Is it really farming? The study by Ren et al in Science Advances paper is important-- it represents the largest collection of Cannabis genomes sequences, it provides some important information on subpopulations and genes that have been selected for differently in fibre hemp from drug strains. However, I finds is dicussion and conclusions riddles with both imprecision (about chronology, geography and cultures) and inaccuracies. So what should be questioned?.

A major source of inaccuracy lurks in sampling and geographical representation. This is compounded by the fact that in many countries growing or collection or transporting of Cannabis is illegal (although legalization is on the rise). Thus traditional drug varieties have not been sampled across most of Central Asian countries, Afghanistan, Russia, Iran. It should go without saying that sampling in the modern time plane will miss past diversity that has been lost to ha bitat destruction and environmental change; such a problem, for example, has plagued some genetic studies of rice-- as wild population no longer exist in the regions were it was first cultivated (such that a modern genome map is not a map of origins). But even so the limited sampling across free-growing (feral/ wild) outside of South Asia and China) is notable. Compare the map of Ren et al (above) with that from the Cannabis book by Clarke and Merlin (2013), which highlight how much more wild/feral diversity there is out there across Asia and eastern most Europe, including 'wild' populations south of ot eh Caspian sea in Iran and along the Volga River in Russia. Even the map from Clarke and Merlin is incomplete with regards to Afghanistan where Vavilov collected apparently wild drug types of Cannabis (C. indiva var. afghanica) in the 1920s.

Given how few wild/feral samples that they have can they really rule out multiple domestications. Genetic analyses often err on the side of single origins. Simulation work (Allaby et al 2008 PNAS) have shown that this will be true even for crops with multiple origins, because gene flow among crops of different origins and pruning of lost branches (not sampled or not surviving to present). Their analytical methods are more modern and more sophisticated but I am not sure they can rule out multiple origins, and they certainly can’t rule out origins from regions not sampled or where wild populations are extirpated (e.g. Japan). Also wild populations (lets assume there are some in central Asia) can be heavily inundated with gene flow from crops over time make their original dinstictiveness hard to find in modern genomes.

A major issue is imprecision in dating. Genomic dervied estimates will never rival radiocarbon dating on archaeobotanical remains. Their proposed date of origins (is this domeatication?) has 6000 year error margins. And it not clear what they date! Was a divergence  between two wild population separated due to climatic vicariance at the end of the Pleistiocene or start of the Holocene, or is it meant to be the domestication bottleneck? The equivalent genomic dates for Asian rice domestication are ca. 18,000 BP and something close to 10,000 for African rice. Both of which are way off. African rice is domestication at more like 3000 BP and Asian rice at more like 8000 BP (of course it matters whether one is talking about the beginning or end of a process, as domestication takes 3000-4000 years in terms of morphological evolution/ genetic fixation.

By contrast archaeological dates are much more precise, at worst with 100-200 year error margins, but Ren at all quote these very imprecisely. It is as if they wish archaeology was less precise, but even then it would not approach the dating imprecission attached the the genomic dates. The say "~3000 BP" for the appearance of Cannabis in India, but if we are rounding off it is closer to 4000, as it occurs in the Late Harappan horizen (3900-3500 BC). Although Indian epics are not well dated some parts of them are from oral traditions that probably also date around then and make reference to Cannabis- I think Ren et al refer to this as ~2000 BP. Cannabis comes to India in my view as part of “Chinese horizon”, which is really just piece meal adoption of various things coming in via central Asia including crops and technologoies (harvest knives) from China, peaches, apricots, millets, japoonica rice. For discussions of this see, for example Fuller & Boivin (2009); Stevens et al (2016). Whether or not it arrived in South Asia earlier, or was already utilized from wild populations in the Himalayas, does not really make much differece to the whether or not cultivation began at the start of the Holocene in China. The imprecision in genetic dating, however, makes it about as likely that domestication took place around the start of the Yangshao period (~5000 BC), the period when we generally see the ending of the millennia long domestication process for the native China millets (

They are also quite imprecise about geography: are they suggesting a NW China (Xinjiang) or NE (Chifeng) source? And if either of these then discussion of early cord-marked pottery in South China (mostly south the Yangtze) is really not relevant, and yet they discuss this as though it indicates the use of hemp cords-- for which there is simply no evidence. 

Cannabis is undoubtedly an important crop brought into cultivation early in east Asia, esepcially for its medicinal and/or social uses, but becoming important for larger oily seeds and fibres over time. But in my view its development as a crop either parallels or is even inspired by the increasing importance of cultivation of other taxa, like the China millets. And this process could easily have played out multiple times-- perhaps in very different contexts in parts of central Asia or Jomon Japan, even amongst non-farming cultures. While genomic data will contribute to this, modelling such data really requires some calibration points in time and space, which will ultimately come from archaeobotany.

Chicken origins: closing in with new genomic evidence

wild Gallus gallus spadiceus

The past week saw the publication of a landmark genomic study on chickens (Wang et al 2020, Cell Research), which clarifies much about origins, and focuses some questions for further research. For a news summary see Lawler's Science piece.

It is transformative because it includes a substantial sample of genomes from across all of the wild subspecies of Red Jungle Fowl (142 wild red jungle fowls) and other wild Gallus species. The first thing to note is that is does support the reality of these different wild taxa. They aren’t merely geographical feral populations derived from escaped chickens, but they are differentiated from each other, making it reasonable to ask which population(s) are ancestral to domesticated chickens. In addition there has, of course, been gene flow via introgressions with domesticated chickens, but this has been on a more limited scale. So the answer to big question (of origins) appears to be Gallus gallus spadiceus. G. g. spadiceus is geographically focused on Burma, Yunnan, Guangxi, northern Thailand and bits of Laos. This struck me as the most surprising—this geographical derivation. If one favours a Chinese origins then you would look to G. g. jaboulliei (of the Guangdong and Fujian and perhaps further north in the past); if one favours an Indus domestication then one looks to G. g. murghii. Previously I have accepted the likelihood of an Indus Chicken domestication and a spread through India in post-Harappan times (e.g. Fuller 2006). This now appears unlikely. Instead it probably means that wild jungle fowls attracted attention in the Harappan period as pretty birds that were captured sometimes, traded, etc.,but not really domesticated subsistence species. Presumably the first Bronze Age Mesopotamian and Ramesside Egyptian “chickens” were actually pet wild jungle fowl-- fancy exotic birds-- and not connected to chickens as we understand them now. The "multi-colored birds of Meluhha" that were imported to Mesopotamia at the end of the Third Millennium BC from the Indus region, are plausible painted ivory statuettes of murghii jungle fowl (see, e.g. During-Caspers 1990).

These new genetic data also make it clear that as chickens spread out of their northern SE Asian homeland they did pickup some genetic material through introgression with local wild jungle fowl (such as G. g. murghii in northern India) and even grey jungle fowl in South India (the source of yellow legs: G. sonneratii). This process can be called “introgressive capture” and it is widespread in most livestock and many crops. This process has sometimes confused genetic studies into inferring multiple domestications, but with more genomic data it can now be disentangled (see Larson and Fuller 2014). 

It is also quite exciting that they have some genetic loci that might be under positive selection as part of the domestication process. One of the real mysteries with animal domestication is what constitutes domestication in a genetic sense in terms of adaptations. In plant it is well known that certain genes for seed dispersal, growth habit, dormancy, grain size, etc. were selected. We can find this evidence genetically and tie it to morphological changes in the archaeobotanical record. There is so far nothing equivalent in animals that links genetic loci to the morphological adaptations we see with animal domestication. So on a more theoretical level this may be the first step to actually starting to unravel the genetics of animal domestication.

These raises fascinating questions then about the contexts in which G. g spadiceus was domesticated—what kinds of human societies and agricultural economies did it interact with in its wild form and how did it get incorporated into ecology of human settlements. Equally at what period and in what contexts did these early chickens then spread. Their phylogenetic results suggest the first wave of chickens spread through SE Asia and SW China only.  Sadly we know little about the Neolithic in Myanmar, or Guangxi or Southern Yunnan; we do have some data from northern Yunnan where Chinese millet and rice agriculture (with pigs) arrives from the North around 2600 BC. One presumes there was some further Southern diffusion towards the China/Burma borderlands. And perhaps it was in these borderland zones where early sedentary rice/millet farmers began to isolate some G. g. spadiceus populations that came feed within the human settlement niche. As hypothesized in Larson and Fuller (2014), chickens likely followed a commensal pathway to domestication. But we now need to refine the map (right). And work out when this happened.

There estimate of the age of the last common ancestor of domesticated chickens and G. g. spadiceus 9500 BP (+/- 3000). But I would regard domestication any time between 10000 BC and 4500 BC as highly unlikely. As the authors themselves not in the first paragraph of their discussion such genetic estimates of domestication age tend to be over estimates (by upto 15,000 years!), so these are not exactly reliable.  In fact I would regard the tendency genetic coallesence ages as to tell us anyting about the timing of domestication to be a highly  misleading tradition that is entrenched in genetics but has little to back it up. Take the example of rice (Oryza sativa), where the genetic estimate of last common ancestor of cultivated rice and modern wild population is ca. 18,000 (Choi et al 2017). But archaeologically even the more generous estimates are ~10,000 (and more like 7,000-6500 by more cautious approaches). I suspect a more general problem is that what is being picked up the last major cladogenetic event that structured wild populations and not domestication itself. Often this can be expected to be something climatic, so 9500 BP is telling us something about how Early Holocene climatic changes—which restructured vegetation in big ways—restructured wild jungle fowl. Then it was one of these localized population that millennia later got domesticated. In all likelihood that localized population that was actually domesticated won’t exist anymore. It is also worth noting that the reality of domestication bottlenecks is itself somewhat dubious and is in the past year or two come to be questioned. Where ancient DNA is available (e.g. maize, sorghum, barley) it is demonstrable that no such bottleneck occurred and age estimates (see Allaby, Ware and Kistler 2019) that conceive some sort of a bottleneck may not be really telling up about domestication. 

Given what we know of the archaeology of SE Asia, one would tend think the initial  domestication and spread of chicken is unlikely earlier than the grain-based Neolithic that starts around 2500 BC (in southern bits of China) and reaches southern Thailand at 2000 BC. However, as far as I know there are no archaeological chicken finds at early sites. So I wonder whether the first spread of domesticated chicken might represent a secondary later spread perhaps closer to 1000 BC (the period when Bronze working spread southwards from China); this might also be the period when new crops spread like sticky rice. It may be that at that time chickens also spread rapidly via trade routes to India. I have long argued (e.g. Fuller 2007) that in South India the Dravidian linguistics suggest arrival of chickens after the South, South-Central and Central languages had fully diverged (which is something like 3000 years ago). Not long after this there are good chicken terminologies in Sanskrits and Prakrits from the 1^st Millennium BC, so it makes sense that chickens really only became established as livestock in India at around that time, and of course it is the later Iron Age when they first turn up in the west , such as the Hellenistic era evidence from the Levant (Perry-Gal et al 2015), or as an exotic animal in western Europe (Sykes 2012).

Structured diversity in tea does not mean multiple domestications

Genetic population structure of tea.

When and where were tea domesticated? And how many times? This is a question I get asked sometimes, and a paper published a few years ago was just brought to my attention that claims to have genetic evidence for three separate domestications, by Meegahakumbura et al. (2016) in PLOSone. I disagree. The paper convinced me of quite the opposite. It remains entirely likely that tea was domesticated only once in ancient times, even if there were widespread use of wild tea leaves across their wild range by people who encountered them-- but a key problem remains determining what that wild range was. The Meegahakumbara paper is an interesting one in terms of raising the question as to how much underlying geographical structure there is in the genetic diversity of tea, and how this relates to different cultural traditions of use, and which (if any) can be regarded to evolving into domesticated forms. But in the end there are severe limitations to their study. Despite some sampling from "wild" populations in India and China, as well as cultivars, there is a lack of samples from in between (northern Vietnam, Myanmar and presumably Laos, which are all presumably within the range of wild teas. What is really at issue is whether or not the large tree forms of tea are primarily wild (and recently managed or cultivated) or represents a distinct domesticated form, and this in turn raises the issues of what is "domestication" in tea. Domestication implies morphological adaptations, underpinned by genetics, which have been favoured through the propagation over generations by people. We know full well what this entails in cereals and seed crops (see, e.g. this Annals of Botany article); we can propose what is involved in tree fruits (which are harvested for fruits and presumably early on cultivated from seed: see "long and attenuated"); and we can also propose what is common about domestication in tubers and other vegecultural crops (see this recent Annals of botany article). But what about tea? Since tea can be propagated by seed or by cuttings it might share some similarities with either tree fruit or vegecultural domestications, but its use for leaf harvesting makes it quite different. Characteristics that might fit in the vegecultural domestication syndrome, include increased proportion of edible (leaf) to inedible (trunk) parts, and more asynchronous production of those. In developmental terms there appear to be selection for dwarfism-- smaller leaves, smaller stature, and more compact growth, which together with human management give teas their very trimmed hedge look (below).

Tea (C. sinensis sinensis) cultivation in Zhejiang
(Photo: DQ Fuller, 2004)

So what did Meegahakumbara et al. find? They demonstrated 3 distinct populations, and a 4th (lasiocalyx) that looks admixed between the Indian and Chinese tree teas (Figure at top). Truly domesticated tea (C. sinensis sinesis) looks to a be a strong clade. That is (in my view) the only really domesticated form. It has distinctive morphology (dwarfism).  It could already be distinct by the Han period, or at least under selection, since small, immature leaves are among the grave goods in the Yangling tomb of a Han Dynasty queen in Shaanxi, indicating trade from distance Yunnan already by 2200 years ago (see this Scientific Report). While it could be that tea was still a wild utilized plant, it might make sense that by this period experiments with cultivation had begun with an ancestral form of C. sinensis sinensis. It is also plausible that some cultivation developed in parallel with the distinct species C. taliensis, but its cultivation never spread beyond the Myanmar-Yunnan border regions (see, this paper on taliensis tea), so it is less relevant to the main domestication story of tea.

But is there any reason to assume that the distinct populations of large tea forms of tea, which they refer to as Assam tea (C. sinensis assamica). They divide this tall tree tea (see left) into two geographical groups (Indian assamica and Yunnan assamica, which leads to the somewhat oxymoronic terminology of "Chinese assam tea"). I do not see any reason in these data, or rationale provided, to not assume that Chinese tea is a domestication bottleneck from the Yunnan tree tea (assamica sensu  lato). The Assam and Yunnan populations of tree teas are distinct as one would expect of any geographically distant populations of a wild species. Trees of this assamica tea are also wild through large parts of northern Vietnam (see Zhao et al. 2017), and I would expect them also in Laos and parts of Myanmar.  In India these tree teas were used from the wild by a few local minority tribes prior to the British introduction of tea drinking and Chinese domesticated tea to India. But these were presumably only ever gathered wild. These Assam tree teas only came into cultivation (equivalent to pre-domestication cultivation) in the colonial era.  though they have now been cultivated by ~200 years, there seems no basis to assign them to domesticated status.

The Yunnan tree teas (What they call Chinese Assam tea) are presumably also native to the forests of parts of Yunnan, where they were also used by indigenous people. In this region their cultivation and management has continued while perhaps unmanaged populations went extinct in the wild. They could still be also the source of domesticated C. sinensis Chinese tea, or related to that source.

Tree (assamica) tea, leaves and fruits
(after a photo in the Hangzhou Tea museum)

The Cambod teas (C. lasiocalyx) look to me like part of the structured variation of a wild species that included geographical populations: i.e that the tea trees of Yunnan, India and adjacent Northern SE Asia (Vietnam, etc) borderlands should probably all be C. assamica (or  C., sinensis assamica, as taxonmically described by Zhao et al. 2017).  In their K=3 structure analysis these are grouped with Indian Assam wild tea trees, so it may be that lasiocalyx is just a northerly somewhat smaller variant of wild tea trees. It is plausible that domesticated Chinese tea came from this Cambod end of the wild range, i.e. further east, like SE Yunnan and is more distance from the Assam end of the geographical variation. It is a pity their is no geographical information on the assamica and lasiocalyx populations-- in terms of where and what habitats they come from. Although with a species like this it is not really surprising if wild populations have been completely lost. One is hard pressed to identify truly wild populations of some of the world's more popular nuts, whether chestnuts or walnuts, as these trees have been so heavily anthropogenically influenced in terms of where they grow.

So the origins of tea cultivation: southwest China, some place and time still to be determined. But the use of wild tea leaves by local peoples, widespread from Northeast India through Vietnam.

On the history of tea, see especially this magnum opus by Van Driem, reviewed here.

Pearl Millet genomics and domestication centre

Modern genomes have the potential to reveal alot about evolutionary history and past geography of a crop. Of course there are some limitation to the degree that it hard to account for extirpated past populations, such as the wild rice that used to grow in central China or the wild pearl millet that used to grow what is now the Sahara. A new study of pearl millet (Pennisetum glaucum) by Bugarella et al (2018) provides a convincing set of deductions from genetic history that infer an origin of the crop in the western Sahel/Sahara around what is today northern Mali/northeast Mauretania (map at left), followed by early differentiation between those of the far west (Mauretania/Senegal), and the eastern Sahel (e.g. Sudan) from those in the core zones of western Africa. Based on spatial simulations that take into account a few archaeological data points they also estimated the onset of the expansion of pearl millet as crop out of its centre of origin a starting ca. 4800-4900 years ago. This fits nicely with current archaeobotany. The earliest, already domesticated, pearl millet is from northeastern Mali in the lower Tilemsi valley between 2500 and 2000 BC. Perhaps a parallel trajectory of dispersal is represented by the Tichitt Tradition of Mauretania (from ca. 1700 BC). What remains an open question is whether these two area represent distinct domestication trajectories (a point suggested by MacDonald et al 2009; Manning and Fuller 2014), much as we see the West Asian Fertile Crescent as a mosaic of domesticators across the region as more or less the same time (e.g.here or there ). The zone delimited by the genetic study could well represent a sort of "West African Fertile Crescent" in which more than cultural groups were in the process of cultivating and domesticating pearl millet during the middle Holocene. The differentiation of a far western genetic groups would then represent dispersal first through the Tichitt-Oualata traditions of Mauretania and onwards to the Sengal valley- which fits with Brunken, De Wet and Harlan's old taxonomic differentiation of a western race leonis (Economic Botany 1977). A rapid and early spread easterns to the eastern Sahel, which was followed by local introgression with local wild populations, is also implied in this genetic analysis, and fits with the albeit limited archaeobotanical evidence for pearl millet (both morphologically domesticated and wild) alongside cultivated sorghum in the Kasala region of eastern Sudan around 1850 BC, just recently published by Beldados et al. (2018). 

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.

A genome map that is not a map of origins (Rice Genetics Watch returns)

Last week Nature ran an article (Huang et al) with the headline that " A map of rice genome variation reveals the origin of cultivated rice." I here to report that this paper does not do what is says. There is nothing obviously relevant to locating where rice was first brought into cultivation, and the claims in the article are misleading and misguided. This is apparently one of most read Nature papers at the moment, so no doubt we will have to face lots of additional confusion over rice domestication-- and I thought there was already enough confused and misguided info out there. I have had several queries on this over the past week, so below is my quick response.

 There is some important data here and details, and much for further critical analysis. BUT: This study changes nothing. Its stated conclusions are misleading, making false unstated assumptions and arriving at unreasonable and unbelievable conclusions.  In a way this mistake was inevitable and obvious. The authors have concluded the the closest wild ancestors to cultivated rice are living wild populations in the  Pearl River basin. The problem is that rice was domesticated not from living populations but from past populations almost certainly from regions where wild rice is now extinct (technically, we would say, extirpated). This study demonstrates that big science and lots of resources do not inevitably produce answers, but that nuanced analysis and critical thinking, and in this case some knowledge of Chinese history, are necessary to direct analyses.

It is clear that wild rice (O. rufipogon) formerly occurred much further north, through much of the Yangtze valley and even as far north as the Shandong peninsula and lower Yellow River basin. This is clearly attested from Chinese written sources of the Song Dynasty (i.e. about 1000 years ago). Even by that period it is likely that wild rice distribution was greatly reduced by the impact of China’s huge human population and agricultural expansion which took place between 6000 years ago and 1000 years ago. More so than anywhere else on earth central China (from the Yellow river  to the Yangtze) has supported massive human populations and suffered the corresponding habitat loss. In the late Bronze Age (Zhou dynasty), they were hunting elephants on the banks of the Yellow river (for a wonderful book on Chinese environmental history that takes this as representative of the broader sweep of Chinese history, see the Retreat of the The Elephants by Mark Elvin 2004). These would certainly not be represented in a genetic study of living elephant populations! (as blogged previously these may actually be an extinct elephant species with straight tusks)

Although reference 2 in the article is to a paper I co-authored (Fuller et al 2010), this study clearly did not take on part of the fundamental implications of the maps and discussion early in that paper about the past distribution of wild rice, which has been modified both by major climatic change since the wetter and warmer early Holocene and by the impact of habitat destruction by Chinese farmers since the Neolithic. Areas that could support wild rice made excellent areas for agricultural reclamation: domesticated rice replaced wild rice over much of its original range in central China, which had the highest human populations. Even clearer, I think, is the paper I published in the journal Rice in 2011, which includes maps and a phylogenetic diagram illustrating the fallacy of using modern extant wild rice to represent the full diversity of past wild rice. By making this assumption in pinpointing a pearl river origins for rice pretty much all the authors subsequent conclusions are inevitably problematic. The  only way oin which genetics is going to advance pinpointing the number and location of domestication events in rice is through the recovery of ancient DNA. The fallacy an approach that relies purely on the modern time-frame of sampling is well-illustrated with European pigs and boar genetics, in which only via recovery of ancient DNA is it possible to see that the first Neolithic pigs were derived from Near Eastern boar and pigs but were later replaced by genetics from European wild boar (see: Larson G, et al. (2007).

That modern populations of Oryza rufipogon are not the direct ancestors of japonica rice is implicit in the data in fact. The “obvious genetic distinction between japonica and Or-IIIa (Fig. 2a)”, implies that domestication rice and South Chinese rufipogon are in fact not really so close, just the closest available in linving populations. The intermediates found with Or-1 and indica are because Indian wild rice have been less decimated by the combination climatic changes and human impacts. Indeed this pattern is not new, but was already evidence some years ago, especially in the study of Cheng et al 2003. (Polyphyletic origin of cultivated rice: Based on the interspersionpatterns of SINEs). —this is discussed on the basis of the more detailed Ohtsubo et al paper or 2004 in my 2010 paper and various earlier articles in the archaeological literature). It is nice to see a much larger dataset in the this new paper re-affirm the results of the  p-Sine study, but there is not really anything new accept that the present authors have tries to grab a headline by claiming a Pearl River  origin for rice. It is the populations that bridge the gap between OR-IIIa and japonica which are crucial and these must be extinct populations of Oryza rufipogon that were brought into cultivation in the earlier Holocene. Geographically, this points back towards the north and the Yangtze.

The authors have found more extensive evidence that most domestication genes were selected in japonica and then entered indica through hybridization. Some geneticists, like the Japanese scholar Y-I Sato, or Susan McCouch at Cornell have been discussing this for years, and evidence for this has been mounting—you will also find discussions in the "rice consilience paper" or the "pathways to Asian civilizations" paper. It is misleading, however, to speak of this as “introgression” which implies that pollen flow from domesticated japonica into wild populations in India created indica. What is missing here, and clearly absent from this study, as it was from the Molina et al PNAS paper last year (see previous blog), is consideration of the chloroplast genome. This is older work, but really key, because chloroplasts are not carried in pollen. The Chloroplast (cpDNA) genome of indica and japonica are completely different. Thus introgression by pollen flow from japonica into wild rices is a very convoluted way to account for this hybridization as it would require domestication genes to then persist in wild population that were then re-domesticated. More reasobale in the model I have been promoting as the “proto-indica”model in which wild ancestors of indica (with indica chloroplasts) were under early cultivation or management and the were improved by hybridization with introduced japonica. This does not require domestication gene to somehow persist in wild population where they would be selected against (actually I would expect such introgression to lead to the evolution of weedy rices by "de-domestication": see this blog: ). It also implies a role for human agency in this hybridization process. This means that there were separate starts to cultivation (the human behaviour) for indica and japonica even if the domestication syndrome was shared and evolved one time. 

Does genetic evidence on its own trump fossil evidence? No. Archaeological evidence, which is a fossil record of past rice and past human activities, has once again been simply ignored! Archaeologically early farming societies, with sedentism and villages and evidence for rice cultivation and rice undergoing morphological changes of domestication are found only in the Yangtze valley, as you probably well know. There is no equivalent evidence from Guangdong/ Pearl River. In fact when rice in the Lower Yangtze is showing morphological evolution under cultivation, i.e. between 5000 and 4000 BC, in the Pearl River and South China there are only sparse populations of hunter-gatherer fishers, represented mainly by coastal shell midden sites. These sites provide the earliest evidence for ceramics in the coastal zone (more than 10,000 years later than pottery in the Yangtze!). The first agriculture, based on rice, was introduced between 5000 and 4000 BP, although finds remain few and focused on the southern mountain slopes and north of the Pearl River delta. By this time the Lower Yangtze support urban sites, such as Liangzhu, support by extensive paddy field systems and intensive cultivation of fully domesticated rice. It makes no sense for rice domestication to be placed in the Pearl River region

Weed evolution by de-domestication: the case of rice

The study of weed origins and evolutionary history is the poor cousin of the archaeobotany of crop domestication. Archaeobotanists can potentially do much more on this, and undoubtedly should. To provide some inspiration it is worth considering some recent insights from genetics, to do with weedy rice. While it is surely the case that rice's wild progenitors may act as weeds in the crop, it now appears that much weedy rice is descended from the crop and not directly from the wild progenitor. A recent paper in Genetic Resources and Crop Evolution by Zhang et al. explores the variation in weedy rices in southern China (Guangdong) and northeast China (Liaoning). In Liaoning there are no wild progenitor populations so it is cultivated fields or their margins which provide the only real habitat for spontaneous rices. In Guangdong by contrast there are populations of wild O. rufipogon. Based on microsatellite markers they show that weedy rice in each region clusters with crops, which represent indica and temperate japonica rices, and the weedy rices are distant from true wild populations. They take this to support the hypothesis that weedy rice is secondarily derived from the crop.

Last year this hypothesis also got support from an anatomical study of weedy rice in the USA, by Thurber, Kepler and Caicedo in BMC Plant Biology which shows that the abscission layer which leads to shattering is clearly distinct from non-shattering domesticated rice but also differs from shattering wild rices in terms of its timing in development: it breaks down sooner leading to earlier shattering than in wild rice. This presumably is an useful adapation for beating the farmer to it and getting into the seedbank before the rice harvest. Thurber et al conclude that this points to unidentified regulatory genes that allowed weedy rice, derived from the crop, to reacquire wild-type shattering. (Whether one might be able to tell weedy from wild rice on the physical remains of spikelet bases is another matter, but surely worthy of investigation by an archaeobotanist!). What is more,  genetic characterization (Thurber et al 2010 Molecular Ecology) found that these weedy rices all possessed the sh4 mutation that characterizes domesticated non-shattering rices! This points unambiguously to the acquisition of a different novel mutation that allows shattering. A few years ago Londo & Schaal (in Molecular Ecology) did some haplotyping of American weedy rices and found mutliple origins, with haplotypes from japonica, indica and aus rices (as well as some hybridization).

So rice has a proclivity to weediness, as with many other crops, and the wild progenitor per se may be less to blame. Contrast this with crops that have been domesticated from weeds (oat, rye, kodo millet) and we can begin to think about alternative pathways to and from being a weed.

Pearl millet demographic modelling: 3rd millennium BC and importance of flowering time

A new article in Molecular Biology and Evolution by Clotault et al "Evolutionary History of Pearl Millet (Pennisetum glaucum [L.] R. Br.) and Selection on Flowering Genes since Its Domestication" has some exciting and intriguing results. They have done demographic modelling, using a number of different scenarios of gene flow, based on 20 random genes, and they have also looked for selective sweeps, finding evidence for strong selection on flowering-time related genes. Although they have only modelled single domestication scenarios (which is by no means a done deal in Pearl millet), they have nevertheless taken into explicit account the notion of protracted domestication process (sensu Allaby et al 2008 or Allaby 2010), with gradual fixation of domestication traits, with exponential rather than instantaneous population growth after the bottleneck. 

They find a bottleneck strength and reduction of genetic diversity that fall amongst those estimated for other crops. Their estimated time for domestication returned an intriguingly plausible 4800 years ago, just a few centuries before the earliest archaeological evidence for domestication pearl millet in the Tilemsi valley (see Manning et al, blogged previously). The evidence they have found for selection on flowering related genes makes a whole lot of sense, because the dispersal of pearl millet from a Sahelian zone southwards crossed many different ecological zones, for which adjustments in seasonality would indeed have been important.

Rice archaeology linguistics and genetics special issue

The special issue of Rice arising from the Cornell rice, genetics and linguistics meeting is now complete and fully paginated. I have blogged several of the papers earlier (listed below).  Those papers in the issue are well summarized in the editorial: "In this issue, 12 articles and 1 of the symposium discussants’ commentaries have been included. The first four (by Fuller, Bellwood, d’Alpoim-Guèdes, and Castillo) review and expand the archaeological knowledge about early agriculture in Asia and its wider region. Fuller, who served as a keynote speaker at the symposium, pays special attention to the pan-Asian context, as well as to South Asian developments. The next four articles (by Sagart, Bradley, Southworth, and Whitman) treat the same scope of issues from the perspective mainly of historical linguistics. The contribution by Sanchez-Mazas and her colleagues offers an updated perspective from human genetics, and the two following papers (the first by Takashige and his colleagues and the second by Hsieh, Hsing, and their colleagues), from plant genetics, also reconnecting to the multidisciplinary aspirations of the symposium. In addition, we publish a paper on inter-Asian rice exchanges in later historical periods by veteran agricultural economist Randolph Barker, as well as the revised remarks by Richard O’Connor, one of several symposium discussants."

Amongst the later published papers is piece by the Linguist Frank Southworth, mainly focused on Dravidian India. Of particular note is the reintroduction into main stream linguistics of the "Elamo-Dravidian" hypothesis.

Here are the full list of papers. They can be found on-line here.

Pathways to Asian Civilizations: Tracing the Origins and Spread of Rice and Rice Cultures.  Dorian Q. Fuller

The Checkered Prehistory of Rice Movement Southwards as a Domesticated Cereal—from the Yangzi to the Equator.  Peter Bellwood [blog notes]

Millets, Rice, Social Complexity, and the Spread of Agriculture to the Chengdu Plain and Southwest China.   Jade d’Alpoim Guedes [blog notes]

Rice in Thailand: The Archaeobotanical Contribution.   Cristina Castillo  [blog notes]

How Many Independent Rice Vocabularies in Asia?.   Laurent Sagart  [blog notes]

Proto-Tibeto-Burman Grain Crops.  David Bradley  [blog notes]

Rice in Dravidian.  Franklin Southworth

Northeast Asian Linguistic Ecology and the Advent of Rice Agriculture in Korea and Japan.   John Whitman [blog notes]

A Genetic Focus on the Peopling History of East Asia: Critical Views.  Alicia Sanchez-Mazas, Da Di and María Eugenia Riccio

Evaluation of Genetic Variation Among Wild Populations and Local Varieties of Rice

Takashige Ishii, Takashi Hiraoka, Tomoyuki Kanzaki, Masahiro Akimoto and Rieko Shishido, et al.

Studies on Ancient Rice—Where Botanists, Agronomists, Archeologists, Linguists, and Ethnologists Meet.   Jaw-shu Hsieh, Yue-ie Caroline Hsing, Tze-fu Hsu, Paul Jen-kuei Li and Kuang-ti Li, et [blog notes]

The Origin and Spread of Early-Ripening Champa Rice: It’s Impact on Song Dynasty China. Randolph Barker

Discussant’s Remarks: Reviving Ethnology to Understand the Rice Neolithic. Richard A. O’Connor

Concatenating rice and language phylogenies: a recipe for single origins?

The literature has been and remains split on singular or multiple origins for rice. The discussion of whether or not all Asian rice can be traced to a single domestication event and a single cultural origin of cultivation continues, and there have been major arguments in favour of it this past year including the high profile genetic modelling paper by Molina et al published in PNAS in May, and a recent contribution on the historical linguistics front. I remain in favour of multiple origins [as per the "rice consilience" paper of last year] -- at least in terms of multiple starts of cultivation of wild rice even if not all of these starts lead on real domestication (in morpholoigcal adaptation terms) or to rice lineages still with us today. Increasingly I am coming to think that modern time-plane sampling, such as modern germplasm or modern minority language vocabularies, is biased by missing out on past diversity-- extinct landraces and wild progenitor populations, lost language diversity. Less diversity sampled will surely tend towards simpler historical reconstructions. Both disciplines also have a predilection for simplifying relationships as trees, which tend to favour single origins. Is there a sense in which genetics and historical linguistics together will tend to be biased towards identifying single points of origin? If so, then when there is evidence to contrary it should surely be given extra weight. A clearly there is an important role for archaeology to try to reclaim some of the lost diversity of the past.


Linguistic homeland for rice?

The new article on "the ethnolinguistic identity of the domesticators of Asian rice" has been published linguist George Van Driem, one of the foremost experts of Himilayan languages many highly obscure and dwindling, especially of the Tibeto-Burman language family has made numerous stabs at the contentious prize of correlating rice agricultural dispersal with historical linguistics, and its inferred history of population movements. In general it provides useful overview of the Austroastiatic and Hmong-Mien reconstruction relating rice and arguments about the homelands of these reconstructed proto-languages. Most archaeologists are probably more familiar with the hypotheses of Peter Bellwood and Charles Higham focused mainly on the Austronesian and Austroasiatic languages in Southeast Asia. (For two recent summary papers by Bellwood, from 2011, see Current Anthropology and the journal Rice). However, there has been considerable recent debate over how Sino-Tibetan (or Tibeto-Burman) languages fit in. The French Linguist Laurent Sagart, an the the instigator of a recent  Cornell conference on the rice and language, has argued in recent years for a shared ancestry of Sino-Tibetan and Austronesian, with an outward migration of rice and millet (Setaria) farmers from central-Eastern China. Van Driem tends to have more of an emphasis on Southwest China through Assam/Burma as a focal area, although he also postulates southwards migrations of  early Hmong-Mien speakers--  likely domesticators of rice (perhaps along the Middle Yangtze). Domestication of  rice by Austroasiatic speakers could have been separate although he seems to tend towards wanting a single origin. As for these Austroasiatic domesticators he places them  somewhere like Assam-- "the Northern Bay of Bengal littoral" (but I presume he does not intend of coastally adapted culture?). In this article Van Driem points to the recent Molina paper as simplifying matters of rice origins, allowing for early cultivation in India to be dismissed. In general the Molina paper and the earlier Londo et al (2006) map are used to suggest a northern Southeast Asia/NE Indian focus for rice domestication, while archaeology is cited mainly for failure to have worked in the required areas. While I would be the first to argue that we need archaeobotanical sampling across Southern China, Burma and Assam I think this paper put too much stock on modern time place samples (languages and genes) and lacks a full engagement with the material constraints that archaeology already provides-- good dates for a domestication process in the Yangtze, good dates for when cereal agriculture, fully formed, arrived in Thailand or Sichuan (e.g. recent blog). These make a dispersal into the Yangtze from a single origin elsewhere impossible, and a dispersal of early rice use into India unlikely (although later introduction of domestication genes is another matter). I do regard as plausible, even likely that there was a separate domestication pathway in the unsampled area, perhaps associated with Austroasiatic, but this must have been in addition to what was happening in the Yangtze and the Ganges. There is a likelihood to would related to the aus-rices-- a group not incorporated in the Molina et al model.


Maps based on modern/recent distributions are a recurrent weakness in the paper. Modern wild rices, like those mapped following Londo et al (or Sampled by Molina et al) are of course biased towards the more tropical South as wild rices are not extant in most of the Yangtze nor in eastern China, but this is a product of environmental change both climatic and anthropogenic-- the extirpated wild rices of the Lower Yangtze, Huai, southern Shandong are of course missing from modern sampling, but archaeobotany has the potential (and is) putting this on the map. Much of the paper  considers the linguistic paleontology for the homeland of  Austroasiatic, in the case of the latter providing a series of maps of fauna that reconstruct to Proto-Austroasiatic, which point towards a southeast Asian (or Southernmost China) distribution. While these provide an important starting point they are also biased towards modern geography rather than early/middle Holocene geography. To take two examples consider water buffalo and elephants, both mapped as going as far north as southern fringes of the Yangtze. But both are species that we know used to range into and north of the Yellow River valley at least through the Bronze Age (i.e. until perhaps 1500-1000BC). Hoffpauir's (2000) excellent chapter on the Water Buffalo in the Cambridge World History of Food provides a good map while a more schematic map occurs in my 2007 paper on non-human genetics, agricultural origins and linguistics in South Asia [pdf]. As for the elephant its former northern occurrence apparently even for Shang royal elephant hunts, provides the leitmotif and title for an excellent long-term environmental history of China,

Mark Elvin's The Retreat of the Elephants. Compare Van Driem's map (top/left) and Elvin's retreat map (lower/right)

[note added 30 Dec. 2011: I have just come across the study by Li et al. (in press in Quaternary International) which has identified Early-Middle Holocene and Bronze Age "elephants" of northern China as the extinct Palaeoloxodon straight-tusked elephants rather than modern Asian elephants (Elephas maximus) but the point still stands since either could the be referent of an early etymon.

As for the genetic single origin (of Molina et al.)

Molina et al (2011a) carried out analysis of demographic history by attempting to model demographic parameters from several phylogenetic datasets using the new generation of collascent models (BEAST and DADI) which allow for multiple branches, bottlenecks and populations. This represents an important step away from single bottleneck models (e.g. Zhu et al 2007; Zhang et al 2009) which only attempted to estimate the correlation between early population size and length of the domestication (bottleneck period) of a single hypothetical origin. They conclude that single domestication of japonica is likely with indica derived from a subsequent bottleneck (underlying grey image below left), their discussion later hedges this with raising the importance of hybridzation/ introgression in indica, although the headline that most take away from this paper is still the idea of a single origin, single domestication event. However origin (start of cultivation) and domestication may not be the same thing.

 This study, however, does not sway me from my conclusion about the evidence for a proto-indica exploited in India before the introduction and hybridization with improved japonica, but reinforces the need for a fossil record. They are unable to sample and model the full range of diversity in all the lineages that have ever been cultivated, however briefly, over the past 8000 years. Their work focused on nuclear genetics, undoubtedly the most informative about evolutionary history in general, but they over overlooked the chloroplast. The chloroplast, which is maternally inherited, differs fundamentally between indica and japonica, nivara and rufipogon, such that there are shared characters between indica and nivara which differ with those of japonica and rufipogon, while other characters in indica are unknown in the wild. This set of chloroplast relationships is indicated in the color overlay in Figure. While they conclude that introgression, which I take to mean pollen flow, from wild rice (into the crop) in India might account for some of the genetic diversity in indica not seen in japonica, it cannot account for the chloroplast diversity, since chloroplasts are not carried in pollen. Thus pollen from wild Indian rices introduced to japonica is insufficient explanation. Instead one would have to posit pollen flow from crops into wild populations (with some nivara-related traits and some now extirpated traits) and that those wild populations retained domestication traits and were subsequently brought back into cultivation. Instead it seems still easier to posit proto-indica cultivation into which cultivated japonica , with a suite of valuable domestication traits, was brought into contact. The genetic background was largely indica into which japonica was the source of introgression, i.e. pollen flow.   I also worry the discernment between their alternative models is not very clear; comparing visually the differences in predicted outputs and actual data (Figure S4 of Molina et a 2011a) it is hard to see much of a dramatic difference between either predictions or fit. In the end I worry that they are forcing us to choose a false dichotomy between common ancestry and gene flow for explaining similarities between indica and japonica, and favouring shared ancestry on the basis an averaged phylogenetic tree across several datasets which may favour a single origin for domesticates much as is true of the neighbour-joining analysis of neutral genetic variation (Allaby et al 2008 or Allaby et al  2010 ).

Something that can certainly be remedied in the next round of models is the exclusion of temperate japonica, which was excluded from the sample set of Molina et al. As we see in the spread of rice in China, it enters the temperate zone of North China already by 3800 BC (based on a direct AMS at Nanjiaokou), where the short-grained is already evident. Based on environment and grain morphology then, we can infer the temperate japonica evolved (through its own post-domestication bottleneck) quite early. It is also from this region (the Yellow River) that diffusion westwards to central Asia and Northwest India is most likely. Therefore I would envision an early form of temperate japonica making the first hybrids with proto-indica. The sequence of bottlenecks associated with rice dispersal event was surely more than two, and some of these may have been associated with quite strong selection pressures (such as for or against photoperiodicity) as rice adapted to new ecologies: just two bottlenecks is unrealistic.  

Nevertheless Molina et al provide what probably a more realistic molecular clock estimate than has been possible before, with an initial domestication placed at 8200 BP (upto 13000), and the indica bottleneck at ca. 3900 BP. The former fits quite well with current archaeobotanical evidence for the beginnings of morphological change in Yangtze rice, and the later  date is spot on for the first appearance of the “Chinese horizon” in Pakistan and Northwest India. If this study is taken as representing the main stream of fully domesticated rice then it seems to be closing on elements of reality.

I would regard many of the problems identified above as conceptually relevant to historical linguistic hypotheses. Linguistic reconstructions inevitably work backwards from a modern time plane (although some may benefit from old texts too), towards a reconstructed common ancestor. This is like the domestication bottleneck in that while its form may be inferred from the modern data (given certain simplifying assumptions), lost side lineages, may be overlooked, and shared ancestry may therefore be easier to see than parallel developments. The dominance of the single japonica narrative found by Molina et al. (2011a) is much like the dominant Austronesian paradigm in its downplaying of substrates and language levelling processes. Indeed, recent perspectives on the later history of Southeast Asia, such as James Scott's (2009) The Art of Not Being Governed, have emphasized that ethnic affiliation has been flexible and that disgruntled overtaxed rice farmers have recurrently taken to the hills and joined the shifting-cultivator tribes, switching identity and language (at least for the past 1000 years). This is probably one factor contributing to the remarkable typological convergence across Southeast Asian language families and this may obscure early history. I find this conceptually similar to the observation that over time domesticated crop varieties come to resemble each other more than any resemble wild progenitor populations, leading to false ascertainment of monophyly (Allaby et al 2008; 2010).

. . .
My own working hypotheses on how rice phylogenetics and especially historical linguistics can be fit together within the framework of evidential constraints provided by archaeobotanical evidence, should be published soon in a special issue of the journal Rice [on-line here] arising from the Cornell conference....let the discussion continue and may it inspire new archaeobotanical sampling and genetic modelling. 

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!