Written by: Henry Ertl
Edited by: Ryan Schildcrout, Madeline Cooke, Austin Shannon, and Madeline Barron
There are many reasons why I’m not proud of shopping at Whole Foods. Near the top of this list are the “GMO-free” icons plastered everywhere denoting that a given food product is free of genetically modified organisms (GMOs). Even though GMOs are increasingly common, people of many backgrounds have strong feelings against GMOs, claiming they’re unsafe, unethical, or unnatural. Perhaps the only group consistently advocating for GMOs (aside from the CEOs of big agricultural companies with billions of dollars at stake) are scientists driving their technological advancement.
As a molecular geneticist, I’ve defended the use of genetic engineering in agricultural crop development because (1) there is scientific consensus that GM foods are safe and (2) GMOs are no less “natural” than crops developed centuries ago. The latter point is based on the logic that humans have been shaping plant genomes and taking them out of their “natural” context since the dawn of farming, and genetic engineering approaches are but a minor extension of this history. However, as evidenced by my Whole Foods shopping experience, people don’t seem to be buying this argument and, admittedly, I’m not so sure I believe it myself anymore. The agricultural practices that produced the first domesticated crops 10,000 years ago looked very different from the agriculture today – it is too simplistic to equate the two. Perhaps, instead of arguing that agricultural crop development methods have not changed throughout history, it might be more fruitful to explore how they are in fact different. With these differences between contemporary and historical approaches in mind, we can then collectively decide: do these differences matter?
Agricultural crop development from an evolutionary perspective
How can we meaningfully distinguish contemporary from historical approaches to agricultural crop development? Agricultural crop development entails finding and propagating plants with desirable qualities, which relies heavily on directing the evolution of these crops, suggesting that meaningful distinctions might be found within the evolutionary process. There are two evolutionary forces that are incredibly important to the agricultural pursuit of better crops: mutation and selection. Mutations occur when the cell makes a mistake copying its DNA, altering the new DNA sequence. If this happens in reproductive cells, the resulting offspring might have new or different traits. Selection is the process by which certain traits dictate which organisms will either have offspring and continue their genetic lineage or die before producing offspring (Figure 1). Historically, humans have utilized the selective force of evolution to produce new crop strains, but with recent advances in genetic engineering, humans are increasingly taking control of the mutation force as well. By exploring the history of these two evolutionary forces in agriculture, the distinction between contemporary and historical agricultural crop development becomes clearer.
Historical agriculture – the beginnings
Human control over the selective part of evolution coincided with the birth of agriculture. Human agriculture began around 10,000 years ago and, by growing plants, collecting seeds from their best-performing individuals, and replanting the following season, these humans selected which genetic variants were passed onto the next generation. The evolutionary effect of human-directed selection in agriculture has been enormous, as described by Charles Darwin in The Origin of Species:
I have seen great surprise expressed in horticultural works at the wonderful skill of gardeners, in having produced such splendid results from such poor materials; but the art, I cannot doubt, has been simple, and, as far as the final result is concerned, has been followed almost unconsciously. It has consisted in always cultivating the best known variety, sowing its seeds, and, when a slightly better variety has chanced to appear, selecting it, and so onwards.
The evolutionary history of corn exemplifies the power of human-directed selection. Ancestrally a much smaller and tougher plant, Mesoamericans transformed corn by selecting for farmer and eater-friendly traits, such as softer casings and a higher nutrient content. However, in doing so, these humans also created a plant incapable of long-term evolutionary survival outside of a farm. In this sense, corn is very “unnatural”, but the evolutionary path taken was still constrained by “natural” mutational processes. Humans directed the evolution of contemporary corn without having control over the rate or type of mutations, and it wasn’t until 9,000 years after the domestication of corn that we discovered a way to dictate the mutational side of the evolutionary process.
Historical agriculture – the industrial era
By the early 20th century, humans had reached two essential milestones for gaining control over genetic mutations: (1) a burgeoning understanding of genetics and heredity and (2) the capability to generate highly concentrated radiation. This combination led to the discovery that radiation directed at crop seeds heightened the mutation rate in the offspring. Before long, many farmers were growing crops from such radiation-treated seeds in plots that came to be known as Atomic Gardens as part of an initiative to use “nuclear technology for peace” following WWII. Today worldwide, there are more than 2,250 circulating crop strains derived from an ancestral crop treated with radiation. Despite its negative connotations, the correct application of radiation in agriculture is not harmful to human health.
Radiation undoubtedly helped to quicken the pace of crop development by increasing the mutation rate, but where and how these mutations occurred was still left to chance (or, more specifically, the occurrence of mistakes during DNA replication or the random effects of irradiation). Crop developers were still largely at the mercy of biological systems’ “natural” mutational constraints. To circumvent these constraints and direct the mutational part of the evolutionary process, a crop developer would need to make the desired mutations themselves. In other words, crop developers would need to become genetic engineers.
Contemporary agriculture – late 20th and 21st century
Genetic engineering in crops was first accomplished in the late 20th century by geneticists who figured out how to transfer large segments of foreign DNA into plant genomes. With this ability, crop developers were now no longer limited to the small changes that most commonly occur across generations and agriculture was quickly transformed. For example, today, most U.S-grown staple crops such as corn, soybeans, and cotton are now modified with a gene of bacterial-origin that confers insect resistance.
Almost a decade ago, CRISPR-Cas9 was developed, and this new genetic technology enabled geneticists to make any change – big or small – they wanted to a crop’s genome. Although still a technical work-in-progress, the CRISPR-Cas9 system has the potential to be the all-purpose genetic writing utensil. As we continue in this direction of technological development, it is likely we will eventually have complete control over the mutation part – to complement the selective part – of the evolutionary process of crop development.
Does this distinction matter?
From an evolutionary perspective, contemporary agricultural crop development is clearly distinct from historical approaches. Humans have rapidly gained control over the evolutionary processes that create our food, and now we must ask ourselves whether this distinction matters and how we feel about it.
Consider the centrality of food to our identity, both culturally and as a species. Culturally, foods and culinary styles serve as a medium for traditions and experiences to be passed down from generation to generation. As a species, the transition from hunter-gatherer to sedentary farming societies redefined how we feed ourselves and consequently influenced our evolutionary history. Changing once again how we feed ourselves and relate to our food is not necessarily something to be feared and avoided, but it is worth contemplating as we take our first steps into a new era of food.
Note: Some figures for this post were created using BioRender.
Henry Ertl is a PhD candidate in the Department of Ecology and Evolutionary Biology in Trisha Wittkopp’s lab. His dissertation research focuses on the molecular underpinnings of developmental evolution, using fruit flies as a model system. Outside the lab, Henry enjoys searching for a decent bite to eat and then giving his unsolicited opinion of the dining experience on Yelp.