By Amaia Arranz Otaegui
Domesticated cereals such as wheat and barley are nowadays staple-plants in several countries worldwide and they are consumed in popular foodstuffs such as bread, pasta or beer. These plants originated in southwest Asia 10,500 years ago, during the early Pre-Pottery Neolithic B period (EPPNB). In the past 25 years, research into the origins of domesticated plants has resulted in the emergence of two opposing paradigms that explain when, where and why these domesticated species first emerged.
During the 1990s, several scholars claimed that domesticated plants (including several cereal and legumes species, as well as flax) originated in a “core area” located in modern-day southeast Turkey, 10,500 years ago (during the EPPNB). According to this view, the first Neolithic farmers that inhabited the region selected a group of eight plant species to be domesticated, commonly referred to as the Neolithic crop package or founder crops. These included species such as einkorn, emmer, barley, lentil, pea, chickpea, bitter vetch and flax. These researchers proposed that domestication was a rapid process (20-200 years) that occurred as a result of strong human selection. They suggested that domestication occurred as a single event in time, and domesticated crops spread from southeast Turkey to other regions.
Other authors have proposed a completely different paradigm to explain how the domestication process took place. Based on archaeobotanical evidence, researchers have identified that before the development of domesticated plants Neolithic people across southwest Asia cultivated morphologically wild plant species (at least cereals). This process took place during the Pre-Pottery Neolithic A (PPNA), broadly from 11,700 to 10,700 years ago. The evidence indicates that during the EPPNB, the first morphological domesticated plant species appeared (i.e. those that must rely on human intervention for their reproduction), including domesticated wheat and barley. However, these were relatively rare in comparison to morphologically wild species, which predominated during that time. According to the available evidence, it is not until the middle Pre-Pottery Neolithic B (10,200-9,500 years ago) that domesticated crops become widespread in southwest Asia. This evidence suggests that domesticated crops emerged gradually over time, and therefore, plant domestication was a protracted process that occurred in multiple regions.
In our article recently published in PNAS we argue that the earliest signs of domesticated cereals such as wheat and barley are found in southern Syria, around 10,700-10,200 cal BP, whilst in regions such as southeast Turkey, Iran and Iraq, domesticated cereals appear around 400-1,000 years later. This evidence contradicts the presumed role of southeast Turkey as the “core area” from where domesticated crops originated. The study proposes that plant domestication was not only a protracted process, but also occurred at different times depending on the region and the plant species involved. Our research suggests that the chronological difference in the emergence of domesticated cereals might have to do with the type of plant species exploited in each of the regions during the precedent period (PPNA). In southeast Turkey, Iran and Iraq, the exploitation of legumes, goatgrass, fruits and nuts prevailed during this time, whilst in the Levant (modern-day Syria, Jordan, Israel, Palestine and Lebanon) cereals predominated over all other plant foods. Dissimilar plant-based subsistence strategies could have affected the timing for the development of domestication.
In the light of this evidence it is unlikely that all the domesticated crops appeared in a single region or “core-area”, since at least cereals and other crops such as faba bean seem to have appeared first elsewhere. We know that multiple plant species were domesticated during the Neolithic, and it is very likely that in those regions where cereals were not common other plant species were exploited and probably managed. It is therefore time to look ahead and explore the cultivation and domestication processes of plants other than cereals to better understand the subsistence strategies of Neolithic groups at the dawn of agriculture in southwest Asia.