Early Fig Domestication, or Gathering of Wild Parthenocarpic Figs?
Denham, Tim, Antiquity
Kislev et al.'s (2006a) recent claims of fig cultivation and domestication dated to the second half of the twelfth millennium BP in the Lower Jordan valley are sensational. For some, these finds are extremely significant and represent 'the oldest evidence for deliberate planting of a food-producing plant, as opposed to just gathering food in the wild' (Peter Bellwood in Gibbons 2006). There are, however, good reasons why these claims should not be taken at face value.
Kislev et al. (2006a) present evidence of human use of parthenocarpic female figs (Ficus carica var. domestica) from two archaeological sites, Gilgal I and Netiv Hagdud, occupied during the second half of the twelfth millennium BP. The archaeobotanical evidence from these sites is interpreted to represent incipient horticulture and fig domestication based on vegetative propagation, which, in turn, is inferred to have been a common and widespread practice throughout the Fertile Crescent at this time. In this short comment, inaccuracies with Kislev et al.'s understanding of fig reproduction are presented and shown to undermine their proffered interpretations. An alternative, more parsimonious scenario is offered to explain the disproportionate presence of apparently parthenocarpic fig syconia and drupelets at these two sites.
The common fig
The common fig is gynodioecious (functionally dioecious--the sexes are in different plants) and there are two distinct forms of tree, the hermaphroditic caprifig (Ficus carica var. caprificus) and the female fig (Ficus carica var. domestica) (Condit 1947; Storey 1975; Beck & Lord 1988a; 1988b). All fig species are reliant on a symbiotic wasp for pollination and reproduction; for Ficus carica this is Blastophaga psenes (Galil & Neeman 1977; Valdeyron & Lloyd 1979). The discussion here focuses on female figs given that these comprise the archaeobotanical specimens from the Lower Jordan valley.
Female fig trees in the wild yield one main crop of edible figs, which are enclosed inflorescences called syconia (Kjellberg et al. 1987). Among cultivated varieties, female figs produce latent buds that can develop into syconia at springtime to yield a breba crop, with the main crop following. Today, there are three main cultivated types of female fig varieties differentiated according to the characteristics of breba and main crops (after Storey 1975: 572):
* Caducous: those that do not usually produce a breba crop, and drop unpollinated syconia of the main crop;
* Intermittent: those that have a fair to large, parthenocarpic edible breba crop and drop unpollinated syconia of the main crop; and,
* Persistent: those that may or may not produce a parthenocarpic breba crop, and retain unpollinated edible syconia of the main crop.
The production of a breba crop and retention of unpollinated syconia, the latter often termed parthenocarpy, are traits that fluctuate widely among cultivated fig varieties.
Parthenocarpy, or persistence of the unfertilised syconia, in figs can be vegetative or stimulative. The latter is sometimes referred to as induced parthenocarpy when undertaken during modern experimental cultivation using chemicals and hormones (e.g. Crane & Blondeau 1949). Vegetative parthenocarpy arises through a genetic mutation and can be transmitted to progeny through seed, as well as via vegetative propagation (Saleeb 1965; Storey 1975; Awamura et al. 1996), although its frequency in wild populations is likely to be low (Kjellberg 2006, pers. comm.). Stimulative parthenocarpy occurs when a symbiotic wasp enters the syconium of a female fig tree and places its ovipositor in long-style flowers without laying eggs, although other mechanisms are also known (Storey 1975: 580). Parthenocarpic figs produce syconia containing embryoless, or poorly developed, drupelets; these are called 'seedless'.
Errors and omissions
Of greatest concern, Kislev et al. …