Until now, how chickpeas spread throughout the Middle East, South Asia, Ethiopia and the Western Mediterranean has been unclear. Chickpeas are “an essential source of high-quality protein, ranked third among legumes in terms of grain production,” a peer-reviewed research paper by two American scholars and one Russian scholar begins.
“According to archaeological records, chickpea was first domesticated in the Fertile Crescent about 10,000 years BP (Before Present),” they said. “Its subsequent diversification in the Middle East, South Asia, Ethiopia and the Western Mediterranean, however, remains obscure and cannot be resolved using only archaeological and historical evidence.”
The geographic origin of chickpea varieties
As such, their study, published recently in Molecular Biology and Evolution, aims to shed light on the effects of human migration and trade on chickpea’s genetic heritage, including its two types: “desi” and “Kabuli,” which differ in color and size and for which – at least until now – the geographic origin has been a mystery.
The paper noted that genetic clustering of the chickpea by other researchers revealed five centers of chickpea diversity in the Old World: the Mediterranean, Central Asia (Uzbekistan), Near East (Turkey and the Black Sea), South Asia (India) and East Africa (Ethiopia). However, the exact dispersal and genetic mixture or “admixture” history of the chickpea in the Mediterranean Basin and to Ethiopia remains unclear.
The researchers took genetic data from 421 chickpea landraces collected in the 1920s and 1930s representing both the desi and Kabuli subtypes from nine different geographic regions: Northern Mediterranean, southern Mediterranean, Turkey, Lebanon, Ethiopia, the Black Sea, western Uzbekistan, eastern Uzbekistan and India. To test hypotheses of chickpea migration and admixture within and between significant regions of cultivation, the researchers developed two new models: population dispersals (“popdisp”) and migrations and admixtures (“Migadmi”).
Popdisp, a Bayesian model of population dispersal, was used to understand how chickpeas dispersed within each of the geographic regions, comparing two scenarios, one in which chickpeas spread along historic trade routes and the other in which they were distributed linearly, regardless of intervening geographic barriers.
“Our study reveals an intriguing finding regarding the genetic relatedness among chickpea landraces in different geographic regions,” said Anna Igolkina of Peter the Great St. Petersburg Polytechnic University. “Contrary to the assumption that genetic similarity would be determined by linear distance, our results suggest that it is more influenced by human movement costs. This implies that the spread of chickpeas within each region occurred predominantly along trade routes rather than through simple diffusion.”
Migadmi was used to consider the origins of the desi and Kabuli chickpeas by evaluating “multiple and nested admixture events,” including considering “the irregularity of admixture traces along the genome, which can be essential if the admixture event happened far in the past.”
The researchers found both Indian and Middle Eastern traces in Ethiopian chickpeas.
“Ethiopian chickpeas have a unique flavor, with the tartness of the black desi chickpeas that can be found in Indian varieties, but also a hint of sweetness,” said Eric von Wettberg of the University of Vermont. “Previous studies have suggested two possible origins for Ethiopian chickpeas – either an Indian origin supported by morphological similarities, or a Middle Eastern origin given the evidence of human migration from western Eurasia into East Africa around 4,500 years ago.”
Connections between Ethiopia and Jewish people
Previous research has connected Ethiopian highlands to the Jewish people genetically and linguistically; Amharic is considered a Semitic language. Additionally, archaeological evidence dates the arrival of Near Eastern founder crops into Ethiopia at the same time as this human migration. Yet, the chickpeas are smaller-seeded and dark-colored, like most Indian varieties.
“Interestingly, the results revealed that both scenarios may be true, finding that Ethiopian chickpeas share ancestry from Indian, Lebanese and Black Sea source populations,” von Wettberg continued. “The most exciting finding is that Ethiopian chickpeas are a mixture of Middle Eastern and South Asian ancestry. The cultural connection of Ethiopians to the Middle East is widely known, exemplified by their Semitic heritage. Less well known is the extent and importance of Indian Ocean trade routes, which were both an important maritime route of the Silk Road and a way by which agricultural and cultural exchange happened between South Asia and East Africa.”
The same model also linked the origin of the Kabuli chickpea to a local desi chickpea population in Turkey.
“This disputes the linguistic suggestion that the Kabuli type arose in Central Asia and is named after Kabul city in modern Afghanistan,” the researchers wrote.
Igolkina said the research has value beyond the chickpea in that these two new models can be used for future similar work.
“These models can be applied together or separately to analyze migrations and admixtures in other species,” she said. “The core modeling technique used in these models, compositional data analysis, allows for their extension to model multiallelic genetic markers. This is of particular interest when analyzing structural variants, analyses of which are becoming increasingly common.”