Tuareg Trade & Archaeobotany

A new article in the latest Azania (in its new format), reports on the excavations at Tadmakka, in northeast Mali, carried out by Sam Nixon in recent years. These excavations of about 5 meters of stratigraphy produced a wide range of evidence for trans-Saharan trade between ca. 750 and 1400 AD, with a very significant cultural change, interpreted as 'Tuaregization' (a more Nomadic turn) from about 1300 AD. This article focuses on the material culture, the sequence, but includes summary comments on the animals and plant remains. Full details of the archaeobotany (carried out at UCL) are forthcoming.

This site provides the earliest significant evidence of trans-Saharan trade, including specifically gold trade and local gold coin production. Plant evidence also suggests a mixture of local crop-procduction, wild plant gathering and possible trade in grains; of particular interest is the evidence for free-threshing wheats-- but more on that when the archaeobotany is published. Some more information on the project is already available on-line here.

Locating American bean domestications

A couple of recent papers of the UC Davis crops sciences group, continue the research tradition of Paul Gepts in providing further refinements in out undrerstanding of Phaeseolus vulgaris domestications, especially in terms of locating these two domestications and identifying closed related wild popualations.

Kwak and Gepts published in Theoretical & Applied Genetics 118 [March 2009] an open access paper on a phylogenetic and population structure analysis on wild and domesticated beans, reinforcing earlier inferences of separate Mesoamerica and SOuth American origins.

Further details on the Mesomaerican wild populations, their relationships and distributions, can be found in another paper by Kwak, Kami and Gepts (2009) The Putative Mesoamerican Domestication Center of Phaseolus vulgaris Is Located in the Lerma-Santiago Basin of Mexico, Crop Science 49: 554-563. This study concludes that Mexican beans did not originate in the Rio Balsas valley favoured for maize origins--and supported by recent archaeobotany work, but elsewhere in Southwest Mexico. This was on the News feeds of the Crop Society of America last week.

Review on lentil domestication

A recent review article by Sonnante, Hammer and Pignone (2009) " From the cradle of agriculture a handful of lentils: History of domestication" in the rather obscure Rendiconti Lincei of April reviews the archaeology and genetics of Lentil domestication. It provides a useful overview, including a wide range of neutral genetic evidence that confers with the orthodoxy (e.g. of Zohary and Hopf) of a single Lentil domestication somewhere in the Levant, although the authors note the possibility that pre-domestication cultivation began with more than population of Lentils, but in the end only one was domesticated. They also provide a tabulation of the identified domestication-related genes in Lentil, which have generally received less attention than those in peas or Phaeseolus, and discussion of the morphological domestication syndrome in Lentils. They some speculation on why/how people came to cultivate lentils, which remains something of mystery for this and other pulses, in which seed germination rates of wild types are so low as to make them unlikely candidates for domestication. They concur the early Near Eastern agriculture including that of Lentils did not come from a dump-heap origin, but they still suggest that wild lentils might have occurred as weeds in early cereals and thus been a co-domesticate. Given what we know of wild lentil habitats this hypothesis seems little stronger than a dump-heap model, and I must favour some sort of intentional interest in Lentils and other pusles (perhaps for their protein content, or taste, or storability) which lead early cultivators to persist in their efforts despite initially low germination rates.

Rice genetics watch: SNPs confirm widespread hybridization events

Published in PNAS last week was another major genetic study rice genetic diveristy, phylogenetics and genome structure. The study lead of Ken McNally at IRRI, entitled "Genomewide SNP variation reveals relationships among landraces and modern varieties of rice" once again confirmed the wide divergence between indica and japonica, as well as the rather distinct and intermediate position of the aus group of rices, adpated to dry cultivation Bangaldesh and thereabouts. Their summary phylogeny illustrated this clearly:

The dataset set size, in terms of numbers of accessions is quite small (20 selected varieties), but that it made of for this is the large coverage of the genome and the detail of genome structure revealed by its focus on single point mutations (Single Neuclotide Polymorphisms or SNPs). They covered 3.6 million base-pairs of sequence and discovered nearly 160,000 SNPs! In all of this the deep divergence of indica and japonica, which must precede the beginnings of cultivation was indicated. Even if morphological domestication traits are shared (such as the reduced shattereing of the sh4 mutation, or the Prog1 gene for erect growth) this must be attributed to much more recent hybridization probable since the start of management/cultivation. I favour a hypothesis of the introduction of introduce domesticated japonica to the Ganges or Indus where hybridization took place with unimproved proto-indica cultivars. (A key distinction here is between cultivation and domestication). Such a hypothesis, which can explain the genetics of domesticated rices is at odds with claims for an early Holocene rice domestication in the Ganges, e.g. at Lahuradewa, which does not fit with the genetic make-up of modern indica. But such early and important hybridization events were probably not the last.

The key conclusion of this study is that this is evidence for a large degree of hybridization between the different domestic rice clades, i.e, between indica and japonica, and between these and aus. This is an important conclusion, as it means we can not consider the long-term history of these rice lineages as separate but rather we must see them as entangled. With these lineages crossed (intentionally or unintentionally) over the millennia of cultivation to produce a greater range of varieties and adaptations. This may seem obvious but many (most?) prehistories of rice paint extremely simplistic (and unrealistic) pictures, whether one takes common archaeological accounts such as single origins linked to Austronesian or Austroasiatic expansions, or one takes some recent geneticist just-so stories of decreasing 'primitiveness' of rice varieties as one move north or west from Island SE Asia as indicative of an early (and stealth) origin somewhere in the Islands from which Chinese rice derived (e.g. as postulated in the recent Izawa et al. paper).

We can look forward to some future unravelling of the complex, entangled history of rice spreads and hybridizations.

This study got some on-line publicity, e.g. on ScienceDaily, but which seems to have missed the key point about how major hybridization has been in the evolutionary history of rice!

Where from the earliest Old World cotton?

I have received a recent query about early cotton in Nubia and South Asia, vis-a-vis the early occurrence of apparent cotton fibres in plaster from Dhuweila in Jordan (published by Betts et al 1994, J. Archaeological Science). This came in response to discussion of the find in the recent review I co-wrote with Nicole Boivin on the Holocene prehistory of Arabia (including several discussions of crops). I reproduce here my emailed reply as to why I have not committed on the possibility suggested by Betts (et al.) of a Nubia OR South Asian source. I have added links to references cited.

The Nubian source is based on reported cotton from Chalcolithic (A-Group) Nubia, first reported by Chowdhury & Buth in 1970 in Nature. The Indian Expedition to Nubia has preliminary reports on the archaeology in Indian Archaeology: A Review 1961-62 (which can be downloaded), and more extensively in Fouilles en Nubie (1961-1963). The A-Group Nubian cotton is problematic, with criticism published previously be me and by Zohary & Hopf. First it comes from goat dung, which does not necessarily indicate textile processing (admitted in the original Chowdhury publication). Second it comes from an undated excavation where it is alleged to be associated with A-Group ceramics (i.e. 3300-3100 BC-- mid-Third M. BC as cited by Betts [1994] is simply a mis-dating by the Indian archaeologists of 1962 who never got to grips with the Nubian sequence-- the dating of which was sorted out later, e.g. Trigger 1965; but especially Nordstrom 1972, Williams 1986; the region is largely depopulated at 2600 BC except for the Old Kingdom outpost at Buhen), but I am very worried that goat dung containing cotton seeds in Lower Nubia is more likely intrusive from later (Late Meroitic/Post-Meroitic) when cotton was known to be widely cultivated in the region. Stratigraphy in Nubia is always problematic. (I speak from experience in the 4th cataract), due to heavy deflation and reburial with windblown sand. For a published case-in-point consider Wadi Kubbaniya: Late Palaeolithic with charred wild plant remains AMS-dated to 16,000 bp and un-carbonized barley AMS'd at 500 bp [although not from the same excavation season] ! Things get mixed and the depth of deposit at Afyeh where it was found (the Indian Expedition to Nubia) was not very far beneath the surface. If it were from Nubia, how come there are no further cotton finds for 3000 years in the region? (Nevertheless, it would be nice to have more details about the Afyeh excavations, which remain largely unpublished and somewhere in the ASI archives in Delhi). I would note that Chowdhury also identified the Afyeh cotton as G. herbaceum based on a cross section of the seed coat. Perhaps this method works, but I have been unable to replicate it on the SEM (in modern material), which is a pity as it would be great to be able to track the two cotton species from archaeobotanical finds.

In addition, Naive African cotton, Gossypium herbaceum, is reported wild only much further south in Africa. It is of course possible it has gone extinct in Nubia, but if it were in 4th M. BC Nubia then it should on biogeographic grounds have been in Egypt too-- there is nothing in the Lower Nubian flora which is not in Egypt. (Is it likely the Egyptians would have overlooked using a species like this?). But, if one does postulate extinct wild Gossypium herbaceum as far north as Nubia then why not in mid-Holocene (wetter) Arabia as well?

Mehrgarh Period II has cotton seeds and fibres preserved in the earliest copper beads (Moulherat et al. 2004). On present evidence it seems the best, and only reasonable candidate. There can be presumed (but not proven) to come from Gossypium arboreum.

I must admit to remaining perplexed about the Dhuweila find. If textiles were traded long-distance one would not expect them to be valued, not used in tempering plaster. But perhaps this was not a common temper but a rare inclusion where someone tore a frayed tunic or something; the Dhuweila team got lucky-- one would need some systematic and quantitive approach to plaster temper to establish this.

My (obscure) article on Indian cotton and flax archaeology may be of some interest, as it reviews the archaeobotanical finds of these two species in India and Pakistan, with some notes on elsewhere [pdf]. For an updated review of cotton in Nubia see the chapter by Clapham and Rowley-Conwy in the recently published Hillman Feitschrit.

Gordon Hillman honoured with Feitschrift

Yesterday, Gordon Hillman had some surprise visitors, Andy Fairbairn and Ehud Wiess (and I tagged along), who presented him with a feitschrift in his honour, published last week by Oxbow Books, Several years in writing, editing, and production the volume came as pleasant surprise to Gordon.

Gordon is pcitured here with the Feitschrift in his honour and the two editors, his former students Andy Fairbairn (University of Queensland) and Ehud Weiss (of Bar-Ilan University & the Weizmann Institute of Science). This book reflects the wide impact of Gordon's research, teaching and ideas both amongst colleagues (inlcuding junior colleagues like myself), but especially amongst his students, drawn from all over the world).

In typical fashion, Gordon offered us tea but suggested that first we ought to get out and collect some Deschampsia (D. caespitosa, the tufted hair-grass), as it was at the end of its ripening window (of less than 2 weeks or so). With his characteristic enthusiasm and eneregy we headed to Pevensey Marsh with baskets and seed beaters to have a short session at paddling up some spikelets from the extensive stand that grows in an under-grazed area of the marsh. (It has small red grains, not dissimilar from the Ethiopian crop tef in terms of size).

From Gordon Hillman 2 Aug 2009

There was more time spent sitting and eating some fruit (foraged by Andy & Ehud from a supermarket) than actually collecting, with conversation taking up issues of harvesting windows for wild grasses, acorn gathering, processing and tree ownership, seaweed collection and Australian Auracaria pinecones. Having caught up we headed back to Gordon's kitchen to dehusk and grind some Deschampsia and Festuca he had gathered earler in the week and dried. And some simple wild grass biscuits were griddle cooked to accompany our cup of tea.

It is inspiring to see Gordon still add it, regularly out in field and forest, gathering, experimenting with processing and eating. And, he is still working on a book that gathers all of this knowledge and experience on wild food plants together.

The feitschrift contents have been presented previously on this blog. The book can be ordered from Oxbow Books. A full tally of Gordon's published works (so far) can be found here.

Parallel origins: true modern human lithics in India (as true for agriculture)

The latest publication from the Petraglia & Korisettar palaeolithic research team, working in South India, was published last week in PNAS—Population increase and environmental deterioration correspond with microlithic innovations in South Asia ca. 35,000 years ago. This study dovetails nicely with recent simulation modelling effort of some UCL colleagues (Adam Powell, Mark Thomas, and Stephen Shennan, director of the Institute of Archaeology), published in Science last month. (The appearance of these two papers close together is entirely coincidental). This simulations suggest that behavioural innovations, such as modern human behaviour, should be expected to emerge when circumstances are right (especially due to demographic factors of higher interactoing populations), and to be maintained only if demographic circumstances permit (and therefore disappear if populations decline).

These two studies together represent importance counters of an orthodoxy that sees ‘modern’ behaviour as emerging once, and therefore being a great invention when hard cognitive architecture came into place, perhaps even driven by a key genetic mutation for intelligence. Such is the orthodoxy implied by classic textbooks on human evolution, such as by Richard Klein (at least as was used when I was a student) or the recent reviews by Paul Mellars (e.g. his Science paper of 2006). In this view modern humans, heir cognitive abilities and the behavioural application of those abilities emerged once (in Africa) and spread out of Africa (once) to bring intelligent modern everywhere else (perhaps at sometime between 60,000 and 40,000—depending on whether one prefers to emphasize the earliest possible dates for Australia or the Upper Palaeolithic transition in Europe). The evidence from South Asia shows clearly that toolkits were middle Palaeolithic (and in this sense not ‘modern’) from >75,000 to 35,000 years ago, and yet genetics suggests that these would have been anatomically modern humans (and they must have moved through South Asia earlier than their arrival in Australia sometime between 60,000 and 50,000). The bottom line is there is a good evidential case to be made, congruent with the modelling of Powell et al., that the cognitive architecture for modern behaviour was around but the innovations that we regard as ‘modern’ emerged when social and environmental circumstances demanded.

There is a parallel here to where thinking on agricultural origins is moving. There has long been an orthodoxy that agriculture was a great and rare invention, and that agriculture came to most regions by the migration of farmers from a few centres of the influence of a good idea. In the more extreme cases, only 3 centres of origin (Mexico, Near East and China) are accepted. But the evidence of archaeobotany—where it is available—combined with the biography of wild progenitors, and where avail able the genetics of crops/livestock, suggest that there was many more centres in which societies converged on agriculture—the behavioural changes towards manipulation of the environment in favour of the reproduction of a few food species (domestication, the genetic sense, was an unintended consequence of these behavioural shifts, when the genetics of the species allowed). In my most recent attempt to sift through the combined data, I concluded that there is strong case for 24 separate instances of agricultural origins globally—although as many of these are poorly documented and geographically close together one might reduce this to 13, as per the map below from Purugganan & Fuller:

The point is that agriculture, like modern human behaviour, was not a one time great invention, but the product of social and environmental circumstances to which human groups with the same cognitive potential responded in parallel ways. The question in both cases is: what were the common denominators of those circumstances?