=I wrote the following piece as part of a job application - the brief was to take a recent academic article and present and contextualise it for a general audience. Actually, it was a really fun thing to do. This time I've done it on someone else's work, Snir et al's paper last year on the super-site of Ohalo II which has exceptional organic preservation. I've just had a paper accepted on a similar theme, so once that's in print I'll try to do the same thing for it. It's a little less chatty than my usual blogging style, and intentionally more journalistic, but hopefully still engaging.
Weeding out a history
“Proto-weeds” discovered in early cultivation attempts in Israel reveal precursor to domestication, 10,000 years before the onset of agriculture
Over 140 species of wild plants were gathered at the hunter-gatherer campsite of Ohalo II, Israel, c. 23,000 years ago, as testified by the survival of more than 150,000 preserved plant specimens, report Snir et al1. As well as wild cereals, 13 species of well-known current weeds including corn cleaver (Galium tricornutum) and darnel (Lolium tementulum) were found. These finds, with accompanying plant processing technology (flint blades and grindstones), provide the earliest evidence to date of possible small-scale cultivation, 10,000 years prior to the origins of agriculture proper.
Agriculture arose around the start of the Holocene at several global centres2. Prior to this date, however, archaeologists note the existence of ‘niche construction events’3,4, whereby hunter-gatherers altered their landscapes, delivering the necessary preconditions for future domestication: selectively hunting animals, firing vegetation, and selectively gathering and processing wild plants. Such activity is widespread and occurs very early on: wild small-seeded plants including grasses were targeted by hunter-gatherers 100,000 years ago in Mozambique5, 30,000 years ago in Australia6. Such plants were processed into flour or porridge around 30,000 years ago6,7. Such reports often appear as isolated events, but the wealth of global finds, greatly aided by decades-long archaeobotanical effort at sites like Ohalo II8–10, indicate long-drawn out trends, prior to the origins of agriculture: niche construction processes, rather than punctuated events.
Ohalo II, on the shores of the Sea of Galilee, was discovered in 1989, and excavated between 1989 and 2001 to reveal a hunter-gatherer campsite, occupied around the time of the Last Glacial Maximum (c. 23,000 years ago). The site’s importance lies in its exceptional organic preservation, resulting from the charring of over 150,000 plant specimens while the camp was in use, after which the site was abandoned and inundated by the lake, sealing the deposits in an anaerobic environment and preserving the tiny plant remains within.
The origin of weeds, defined in this paper as “plants that disrupt or alter the functioning and composition of natural ecosystems and human-altered environments"1 are largely obscure, as their identification is dependent on the ability of archaeologists to recognise different species, so that, for example, the food crop Eragrostis tef (teff) is not confused with other Eragrostideae. The identification of proto-weeds is key to unravelling early cultivation attempts: at Ohalo II, their frequent presence among future cultivars (such as wild wheat and barley) is said by Snir et al. to indicate small-scale, trial cultivation plots, something which is further substantiated by the presence of distinctive use-polish relating to green cereal harvesting on flint blades, similar to objects seen 10,000 years later, in the Natufian period.
The findings at Ohalo II are important both because the origins of weeds are crucial to detecting the origins of agriculture, but also as a reminder that hunter-gatherers engaged in sophisticated way with their environments. They emphasise that the first farmers arose after millennia of careful (if not premeditated) forager practice. Most interestingly, perhaps, Ohalo II reminds us to question what occurred in regions where such selective practices were occurring at even earlier dates, but where agriculture did not subsequently develop, e.g. southern Africa and Australia. Only archaeobotanical and archaeogenomic analysis will reveal the answer.
2. Zohary, D., Hopf, M. & Weiss, E. Domestication of Plants in the Old World: The origin and spread of domesticated plants in Southwest Asia, Europe, and the Mediterranean Basin. (Oxford University Press, 2012).
3. Odling-Smee, F. J., Laland, K. N., & Feldman, M. W (1996). Niche Construction American Naturalist, 147, 641-648 Smith, B. (2007). Niche construction and the behavioral context of plant and animal domestication Evolutionary Anthropology: Issues, News, and Reviews, 16 (5), 188-199 DOI: 10.1002/evan.20135
=4. Mercader, J. (2009). Mozambican Grass Seed Consumption During the Middle Stone Age Science, 326 (5960), 1680-1683 DOI: 10.1126/science.1173966
5. Fullagar, R., Hayes, E., Stephenson, B., Field, J., Matheson, C., Stern, N., & Fitzsimmons, K. (2015). Evidence for Pleistocene seed grinding at Lake Mungo, south-eastern Australia Archaeology in Oceania, 50, 3-19 DOI: 10.1002/arco.5053
6. Mariotti Lippi, M., Foggi, B., Aranguren, B., Ronchitelli, A., & Revedin, A. (2015). Multistep food plant processing at Grotta Paglicci (Southern Italy) around 32,600 cal B.P. Proceedings of the National Academy of Sciences, 112 (39), 12075-12080 DOI: 10.1073/pnas.1505213112
7. Weiss, E., Kislev, M., Simchoni, O., Nadel, D., & Tschauner, H. (2008). Plant-food preparation area on an Upper Paleolithic brush hut floor at Ohalo II, Israel Journal of Archaeological Science, 35 (8), 2400-2414 DOI: 10.1016/j.jas.2008.03.012
8. Snir, A., Nadel, D., & Weiss, E. (2015). Plant-food preparation on two consecutive floors at Upper Paleolithic Ohalo II, Israel Journal of Archaeological Science, 53, 61-71 DOI: 10.1016/j.jas.2014.09.023
9. Piperno, D., Weiss, E., Holst, I., & Nadel, D. (2004). Processing of wild cereal grains in the Upper Palaeolithic revealed by starch grain analysis Nature, 430 (7000), 670-673 DOI: 10.1038/nature02734