A natural adaptive syndrome as a model for the origins of cereal agriculture

Abstract

A novel explanation of the origin of cereal agriculture is proposed, based on the ecology and adaptive morphology of wild cereals ancestral to our founder cereals (einkorn, emmer and barley). Wild cereals are unusually largeseeded. A natural evolutionary-ecological syndrome relates large seed, awns and monodominance (LAM). Awns bury attached seeds in the soil, protecting seed from fire; buried seed needs to be large to emerge on germination; large seeds, growing without competition from small-seeded plants, will produce monodominant vegetation. Climatic and edaphic instability at the Pleistocene-Holocene boundary would have provided an impetus for the spread of annual ruderal grasses. LAM grassland provided an obvious natural model for the origins of cereal agriculture. Subsequent field management would mimic the natural niche (MNN). The fact that monodominance is a long-standing character of the natural LAM syndrome validates cereal monocultures (now producing most of our food). An alternative explanation of crop domestication, by auditioning a great range of species for a human-constructed niche (NCT), is rejected.

Origins of the Apple: The Role of Megafaunal Mutualism in the Domestication of Malus and Rosaceous Trees

“…As with most domesticated plants, the key to understanding domestication in plants with large fruits rests in a switch from the wild to an anthropogenic seed-dispersal mechanism. Many domesticated crops either possessed weak dispersal strategies in the wild, as is the case in large-seeded cereals (Wood and Lenné, 2018), or had lost their natural seed-dispersal mechanism before humans started more heavily interacting with them, as is the case for many large fruits (Janzen and Martin, 1982; Kistler et al, 2015) or small-seeded grains (Spengler and Mueller, in press). The lack of, or weak, gene-flow regimes in these plants before human intervention left them with a predisposition toward domestication, especially if fragmentary and genetically isolated populations were crossed/hybridized for the first time since the last glacial advance.…”

Anthropogenic Seed Dispersal: Rethinking the Origins of Plant Domestication

“…Rindos recognized the significance of seed dispersal in the domestication processes, and he cautiously stated that the 'evolution of cultivated plants came about by the development of specialized dispersal relationships between humans and numerous previously opportunistically dispersed plants' ( [32], p. 120). Other scholars since then have acknowledged the significance of seed dispersal mechanisms in domestication [33][34][35]; however, few of these studies looked beyond the role of tough rachises in large-grained cereal domestication or nondehiscent pods in the domestication of some legumes. In this paper, I argue that all evolution of plants under the first steps toward domestication, during the early and mid-Holocene (before ca.…”

“…Archaeologists and biologists have studied the switch from the wild to the anthropogenic seed dispersal state in large-seeded cereals and legumes [33,37]. They have studied, in detail, the transition from a brittle rachis to a tough rachis and the role of hygroscopic awns (trypanocarpy) in dispersing and burying large grass seeds [35]. Likewise, studies have illustrated that these cereal crops naturally form dense monodominant fields, which were key for early human harvesting.…”

Fertile Crescent crop progenitors gained a competitive advantage from large seedlings

“…This has been more recently demonstrated through direct comparisons between progenitor and non‐progenitor wild species (Kluyver, 2013; Preece et al., 2015). Other traits that are characteristic of Fertile Crescent cereal crop progenitors are to have an annual life‐form, to be monodominant (form monospecific stands) and to have a ruderal growth strategy, thus to be well adapted to disturbed environments (Wood & Lenné, 2018). However, there are many other annual ruderal grasses in that region that were never domesticated.…”

“…In support of this hypothesis, comparisons between species show that seed size is positively correlated with the proportions of germinating seeds and seedling survival (Baraloto et al., 2005; Chambers, 1995; Leishman et al., 2000; Metz et al., 2010; Wu & Du, 2007), although evidence for negative relationships also exists (Wu et al., 2011). Seeds also have mechanisms for increasing their chances of germination and survival (and reducing those of their competitors), such as the release of chemical inhibitors, which have allelopathic effects (Friedman & Waller, 1983; Kushima et al., 1998; Zhang et al., 2011), and self‐burying awns to avoid predation (Wood & Lenné, 2018).…”