Dong, et al., (Dual domestications and origin of traits in grapevine evolution, Science, 3/3/23) have postulated, based on their study results, a dual origin for vitis vinifera stemming from simultaneous domestications of distinct vitis sylvestris pairs in separate geographic regions. I have previously described the study origin, the history of the progenitor species vitis sylvestris, and the case for dual domestication. In this post I will provide a contemporaneous look at the proposed domestication centers and identify traits selected during the grapevine cultivation process.
The Domestication Centers
The figure below locates the Western Asia (Syl-E1 to CG1) and Caucasus (Syl-E2 to CG2) domestication centers.
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| Grape domestication centers (as per Dong, et al.) |
According to the authors, the dual domestications occurred 11,000 years ago. The Little Ice Age had ended by this time and the world was transitioning from the Pleistocene to the Holocene Epoch.
The Western Asia physical environment was varied, inclusive of highlands, mountain ranges, fertile river valleys, and arid and semi-arid landscapes. Notable geographic features included the Taurus and Zagros Mountains, the Anatolian Plateau, the Levant, the Mesopotamian Plain, and the Jordan River Valley. The Caucasus had a similar distribution of environments but with more prominent mountain ranges. River valleys, such as those hosting the Aras and Kura Rivers, provided conditions suitable for early agricultural development.
The populace of the two centers were mainly hunter-gatherers (hunting, fishing, and gathering), with some early agriculturists. Early farmers likely cultivated wheat, barley, legumes, and flax and domesticated animals such as goats, sheep, and cattle.
It is believed that the Caucasus was inhabited by several indigenous groups but the demographic composition is difficult to determine with any precision. Western Asia, on the other hand, was home to some notable civilizations to include the Natufians (Levant) and the pre-pottery Neolithic cultures of Hassuna, Halaf, and Samarra (Mesopotamia).
Domestication Intent and Thrusts
The authors investigated domestication signatures on the cultivars and found both shared and unique manifestations on the cultivars. Most of the shared signals are on chromosomes 2 and 17, "confirming previous findings that that the selection on flower sexual morphs (sex determination region, SDR), berry skin color (VvMybA gene cluster), and berry development (SDH gene cluster) were of great importance during grapevine domestication." The authors further identified shared domestication genes that possibly serve as foundations for grapevine growth, physiology, fruit set, and resistance to biotic/abiotic stress.
The unique manifestations are exhibited in cases where "the same goals were advanced by using different aspects of common domestication traits." Some examples of the latter are as follows:
- Improvement of berry palatability through the reduction of alkaloid biosynthesis (MecghR gene cluster in CG1 and TR2 and SSL gene clusters in CG2)
- Enhancement of carbohydrate metabolism (SWEET17 in CG1 and PFKFB1 in CG2)
- Perceived berry desirability (BEAT gene cluster for floral scent in CG1 and UFGT gene cluster for berry color in CG2)
- Response to environmental stresses (UPL6 in CG1 and WAK in CG2).
According to the authors, "... their findings suggest that the initial cultivations of CG1 and CG2 may have been to serve early humans' caloric and micronutrient needs." And such an observation fits with the economic environment described previously; that is, a landscape populated primarily by hunter-gatherers and fledgling agriculturists.
In that both cultivars were domesticated as food sources, the selection of factors suitable for winemaking exhibited in CG2 "could have been serendipitous, and the practice of winemaking with CG2 ... possibly postdates grapevine domestication."
In my next post I will examine the spread of these cultivars outward from their domestication centers.
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