They changed history without knowing it.. The ancient Mexicans made clothing for 90% of humanity now sciences

Thousands of years ago, on the Yucatan Peninsula in Mexico, man began a long relationship with a plant that would later change the shape of clothing, trade, and agriculture in the world: cotton, or the master of crops, as Egyptian geographer Gamal Hamdan described it.

Cotton at that time was not a global crop, nor a raw material for a huge industry, but rather a wild or semi-wild plant, sensitive to the length of the day, limited in production, and its fibers were shorter and of lower quality than the cotton we know today.

In a new genomic study published June 22 in the Proceedings of the National Academy of Sciences, an international research team retells this story from within plant DNA.

The team revealed that upland cotton, or highland cotton, scientifically known as “Najdi cotton,” “down cotton,” or “Mexican cotton,” which represents about 90% of global cotton cultivation, most likely dates back to a single domestication origin, and then went through three major stages that gradually transformed it into the modern crop.

The study was based on a broad analysis of what resembles a “major genetic map” of cotton, which included 2,910 samples of cotton and its relatives, including 440 local strains of down cotton that were recently sequenced. Through this data, the researchers tracked the genetic differences between the strains, the transfer of genes between them, and the traits that humans chose over time, such as flowering time, fiber length, and seed weight.

From a wild plant to a global crop

The findings suggest that the story begins with the wild or semi-wild breed known as Yucatanense, which is closest to the ancient form of cotton. From this beginning, cotton entered a long journey of domestication and spread. In the first stage, about 2,800 years ago, the Punctatum strain appeared in regions of tropical Central and South America.

Then came a second phase, about 2,600 years ago, with the rise of the “Latifolium” strain, which researchers believe was the closest ancestor of most modern cultivated cotton varieties.

The third stage was closest to the cotton the world grows today, according to study co-author Luis Rafael Herrera, professor of plant genomics, at the Genomics Institute for Crop Tolerance to Abiotic Stress, Texas Tech University.

The researcher explains in statements to Al Jazeera Net that during this stage, farmers chose plants that flower at a more appropriate time, produce longer and better fibers, and give a higher yield. Choosing the flowering date was not a small detail; Cotton coming from the tropics was very sensitive to day length, that is, it responded to the number of hours of light and darkness per day. This characteristic limits its cultivation in areas far from its original environment.

With the emergence of mutations that help the plant to flower in different daylight conditions, cotton has been able to move out of its original tropical range into wider agricultural areas. That is, cotton did not become a global crop only because humans moved it from one place to another, but rather because its genes changed in a way that made it more able to adapt to new environments.

One of the most important findings of the study was a gene that the researchers called “GHTOFD06,” which is linked to regulating the plant’s sensitivity to light and flowering time.

Genomic analyzes show that versions associated with early flowering have become common in modern varieties, suggesting that this gene was one of the keys that allowed cotton cultivation to expand globally.

Longer fibers and larger seeds

The domestication journey did not stop at flowering time, as researchers also identified a genetic locus linked to fiber length, called “DHFLD11,” and another linked to seed weight and yield, called “GHSID 05.” According to Lewis, these traits are not marginal in the history of cotton: the length of fibers determines the quality of threads and textiles, while seeds affect the economic productivity of the plant, because they are used in food, feed, and other industries.

To understand the role of the last gene more clearly, the researchers experimentally inactivated this gene in modern cotton plants. The result was that the weight of one seed decreased by 11.41%, and the area, length and width of the seed also decreased. This makes the gene a promising target in cotton improvement programs, not only to produce better fibres, but also to increase the value of the seeds themselves.

“The study reveals how domestication worked at more than one level at the same time,” says the study’s co-author. “Ancient farmers did not know the names of the genes, but they chose plants that gave better results: plants that flowered at the right time, produced finer fibres, and had larger or more valuable seeds. As this selection was repeated over long generations, changes in the genome accumulated until modern cultivated cotton appeared.”

The researchers also found evidence of natural gene flow between down cotton and another type, long-staple cotton, which is known for the quality of its fibers in some of its varieties. The researchers believe that this genetic mixing may have added important diversity to cotton, and helped in the emergence of beneficial traits during the course of its domestication and spread.

A map of the past and future

Despite the strength of the results, the study is not without limitations. The analysis of genetic variants was based on a single reference genome, which may lead to some bias and make some structural differences specific to wild or semi-domesticated breeds less clear. Also, some candidate genes, especially those related to flowering timing, require deeper functional experiments to accurately confirm their mechanisms of action.

However, the study provides an important tool for understanding the history of cotton and improving its future. Knowing the genes associated with early flowering, fiber length, and seed weight may help plant breeders develop more productive, better-quality varieties that are better able to adapt to changing agricultural conditions, especially in light of climate change and the increasing pressure on agricultural resources.

The study was funded by several parties, including the Chinese National Research and Development Program, the National Natural Science Foundation of China, research programs in Xinjiang, Hainan and Henan, and the Chinese Academy of Agricultural Sciences, in addition to partial support from the Cotton Foundation Incorporated and the US Department of Agriculture. The researchers declared that there was no conflict of interest.