More Than You Ever Cared to Know About Onions

I have such a thing for plants. They are every bit as exciting and lovely to look at as animals, but for some reason, most people do not agree with me. Sure, they might not be covered in fur (though some plants are covered in these fuzzy hair-like things called tricomes) and sure, they might not purr (though have you heard the wind rattle some old leaves), but they’re really exciting nonetheless. Plants are just stuffed full of chemicals and some of them, the ones we choose to cultivate, have a particularly exciting history that is irrevocably intertwined with our own. Onions are no exception.

Wild onions are found in many regions of the world, but the most common cultivated onion came from Central or Western Asia. Because onions keep well, have some medicinal properties, and make food taste better than ever before, they quickly became a very popular food source. Christopher Columbus tried to introduce the bulb onion to North America, but it turns out it was already there and being used by the people who, by the way, were also already there. Now, many different types of cultivated onions exist, from sweet onions, to green onions, to those nice yellow onions that are so familiar to us all.

All of these cultivated onions are ours thanks to artificial selection, the man-made alternative to natural selection. While both are processes by which evolution occurs, artificial selection differs from natural selection in several key ways. First, artificial selection is directed and natural selection is not. Humans are making choices that drive evolution by artificial selection to a specific end goal. Natural selection doesn’t have an end goal ““ it just occurs as a response to biotic and abiotic pressures. Second, natural selection sort of looks backwards, while artificial selection looks forward. What I mean by that is that natural selection is not planning for the future, but rather is a response to past conditions. Humans, though, do use artificial selection to make strains or cultivars that are best suited for anticipated future conditions. For instance, until a drought happens, natural selection will not select for drought-tolerant plants, but by using artificial selection, humans can create drought-tolerant plants in preparation for a drought. Artificial selection, also, is not the focus of political debates.

Artificial selection and genetic engineering has also been used to explore the possibility of solving the onion-tears problem. Cutting an onion releases some of those delicious volatile compounds and generates sulfenic acids. One of these acids in particular makes us cry. Different onions have different levels of this acid, which is why some types of onions make us cry a lot more than others. Until now, the only solution was gritting your teeth and getting through it or putting the onion in the fridge for a while first to chill it, but now researchers in New Zealand are working to develop a no-tears model, sort of the Johnson and Johnson baby shampoo of the onion world.

I love onions because they are delicious, but I love them a little more when I know where they come from. There is a lot of focus on farm-to-plate information, teaching people exactly where the food they eat comes from and all the inputs that go into that system. I appreciate the good work that is being done in that vein, but, as someone who adores plants beyond most reason, I love knowing what it took for us to get the foods we eat in their current recognizable form.

Michael Pollen’s book, The Botany of Desire, tracks apples, potatoes, marijuana, and tulips in history. While he does not provide enough information to keep a botanist or gardener happy on the science front, the history he explores and the stories he tells us are riveting. But those four plants, while chosen by him with care, are not the only ones who shaped history. Foods, like onions, that grow in many areas and keep well, aided human migration and exploration. Understanding the science of these plants can help us understand our own history.