Peanut Science January 28, 2019
A new study reveals how two ancient species of this legume were combined 10,000 years ago, in Andean valleys, to create the modern peanut
Peanuts are part of cuisines worldwide. Whether as an oil or butter, a snack or an ingredient in savory and sweet dishes, it is easy to find this legume—most often thought of as a nut—in many dishes. But where does it come from? Its origin seems to be in South America, specifically Bolivia, according to new studies.
The modern peanut (Arachis hypogaea) is the result of the hybridization of two older types of Andean peanut. It has 20 pairs of chromosomes—the total from both old species, which have 10 chromosomes each. Scientists always thought—a suspicion now confirmed—that the "parents" of this peanut were the variants Arachis duranensis, very common in the Andean foothills between northwestern Argentina and southeastern Bolivia, and Arachis ipaensis, a species that had been reported but unconfirmed in a Bolivian town several hundred kilometers north, but thought to be extinct, until now.
Researchers at The University of Georgia (U.G.A.) and the International Peanut Genome Initiative, however, recently found a live specimen of A. ipaensis in the Bolivian Andes, and with it the answers to a mystery of how the two ancient species living so far one from each other had managed to hybridize into modern peanuts.
To solve this puzzle, scientists looked up old botanical collections and what they knew about migration patterns and transfers—in accordance with rainy and drought seasons—of the ancient farmers, hunters and food collectors. In addition, researchers used the molecular clock technique—an analysis used to determine, via DNA studies, the time when two species diverge their evolutionary paths to undertake new ones. "We now know that the first inhabitants of South America in their long voyages carried A. ipaensis to the land of A. duranensis 10,000 years ago. Once in the same area, bees pollinized the peanut plant flowers, allowing the birth of the hybrid that our South American ancestors ate and that eventually led to the modern peanut, Arachia hypogaea. It's a fascinating story," says David Bertioli, a researcher at the Center for Applied Genetic Technologies at U.G.A. and lead author of the study, published in Nature Genetics. (Scientific American is part of Springer Nature).
Although it has not been studied how old A. duranensis and A. ipaensis are, researchers think they could be species that have existed for more than a million years, so Bertioli and his team consider them as plant relics. “Having found [A. ipaensis] alive and being now able to study it is almost like taking a look at the garden of these ancient communities. The hybrid peanut crop spread throughout South America in pre-Columbian times, reaching the shores of the Atlantic and Pacific and even into Central America and Mexico. After colonization it was carried to Africa, Asia, North America and Australia, sites where it became an important crop. It is a food that has lived during many interesting times,” Bertioli says.
With a better understanding of the peanut genome, researchers will be better able to identify markers that determine their resistance to certain diseases and weather conditions. This information will allow them to design of genetic variants that are more pest- and drought-resistant as well as more nutritious—a major breakthrough for regions such as Africa, where malnutrition is a severe problem and peanuts are an important source of vegetable protein, Bertioli says. “If we know the genome in-depth, we can have crops that produce more and better results in conditions so far considered adverse,” he adds.
It is worthy to note that botanists do not classify the peanut as a nut, but rather a legume—which is high in protein—that is to say, it is more akin to lentils than hazelnuts.
Still, peanuts offer the same nutritional and health benefits of nuts such as walnuts and almonds but with a clear price difference: U.S. consumers pay on average $5 per kilo for peanuts and $30 for the same amount of hazelnuts. “The difference is in the pocket, but not health,” says Meir Stampfer, epidemiology and nutrition professor at Harvard University’s T. H. Chan School of Public Health and co-author of a study on the benefits of peanuts and nuts published in 2013 in JAMA Internal Medicine.
Stampfer’s work found that people who ate peanuts and nuts regularly were less likely to die from any cause—particularly cardiovascular disease—and that those who ate peanuts obtained the same health benefits that those who ate other nuts.