Pontificia Universidad Católica de Chile (UC): Research on the evolution of corn reveals low micronutrients

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Alejandra Vidal, archaeologist and academic of Anthropology, leads a team of researchers studying how the pre-Hispanic corns found in the Atacama desert have been losing some of the nutritional qualities they originally had. The results obtained so far have been published in the prestigious journal Scientific Reports.

An interdisciplinary investigation of archaeobotany and plant physiology based on pre-Hispanic maize from the Atacama desert is being carried out by Alejandra Vidal, archaeologist and anthropology academic , together with a team of researchers formed by academics Hannetz Roschzttardtz and María Fernanda Pérez , from the Faculty of Biological Sciences , and Mauricio Uribe , FACSO academic, from the University of Chile. The study carried out in recent years has revealed the morphological and genetic change that corn cobs and grains have undergone in more than 2,400 years .

“As an archaeologist, I saw a large number of ears of corn and grains that appeared in domestic archaeological sites, mainly in the Tarapaco area, from Iquique to the interior. Observing these cobs I saw that there were indeed changes in the sizes, in the colors and in the types of grains. Thus, in 2016, the idea arose with María Fernanda Pérez to carry out a systematic evaluation to see if these corns have been selected and modified by pre-Hispanic human groups over thousands of years,” says Alejandra Vidal.

The results that were obtained as the investigation progressed surprised them: the maize had increased in size over time. And presumably this could be due to two phenomena , explains the researcher. On the one hand, due to the selection made by pre-Hispanic human groups and, on the other, –as the results of another parallel investigation showed– due to the fertilization of these maize at a given time. This was demonstrated by the oldest cobs that did not exceed 5 cm. long, unlike others from a more advanced period (Inca period), where they already measured 12 centimeters, with a morphology similar to that of corn that is still found in the northern region.These first findings were published in the journal Plos One .


“As an archaeologist, I saw a large number of ears of corn and grains that appeared in domestic archaeological sites, mainly in the Tarapaco area, from Iquique to the interior. Observing these cobs, I saw that there were indeed changes in sizes, colors and grain types,” says Alejandra Vidal about the beginning of the investigation. Image credit: Alejandra Vidal.
Selection, evolution and micronutrients
The evaluation of plant remains –which appear primarily in pre-Hispanic contexts– to answer questions about the population’s eating habits has been the driving force behind the research led by Alejandra Vidal.

In these studies, maize from various periods have been considered, from some that are around 2,400 years old to contemporary maize , passing through all periods (formative, late intermediate, late and colonial). The loss of micronutrients in cereals such as wheat, rice, barley, and corn was evidenced from the 1970s . The quality measurements of the time showed that after the “green revolution” of the 50s, where “intensive agriculture” was promoted through the selection of seeds to achieve mass production and thus be able to feed the European population and American in the post war period,cereals had lost micronutrients.

“The green revolution fulfilled many of its objectives, but in the 1970s, when they began to evaluate the quality of these cereals, it became clear that in 20 years of intensive selection, they had lost qualities, especially minerals. And, until the day of today, it is not known how this phenomenon occurred in such a short time “, explains the researcher in detail. In other words, the production of cereals had increased in that period, but their micronutrients had decreased, especially minerals as important as iron .

“We realized that, as time progressed, something similar to what happened with the green revolution was happening: iron was being lost and probably because of this intensive selection.” -Alejandra Vidal, anthropologist

Alejandra Vidal specifies that most people do not get iron for their diet through meat, but rather through cereals. “That they were losing iron is critical. The World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) called for trying to understand why these minerals were being lost. We wondered , then, if this has also happened in the past, given that we know that the corns were selected, in a much longer time, not in 20 years, but through several centuries”, comments the academic.

The iron
What did the analyzes of iron in pre-Hispanic maize show? Starting from an exploratory path and without having a clear hypothesis, “to our surprise we discovered that 2,400-year-old maize has a large amount of iron in its cells, particularly in its nuclei”, reveals Alejandra Vidal . “We verified it with more analysis in France and we realized that, as time progressed, something similar to what happened with the green revolution was happening: the iron was being lost and probably because of this intensive selection “. These results were published in the prestigious Scientific Reports last year.

Now, why this low iron occurs is what the Anthropology academic and her team are still investigating, through the genetic analysis of maize . In 2019 they made ancient DNA extractions at the University of Santa Cruz, California, and they already have the complete genetic sequence of eleven ancient corn specimens. With these complete sequences they will be able to continue studying whether there is a selection of certain genes that may be associated with iron metabolism in maize. And they hope to publish the findings in 2023. “It will be relevant, beyond the results, to publish the genetic sequence of ancient maize,” says the researcher.


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