As Thanksgiving approaches in the United States, it’s a good time to reflect upon some of our favorite featured foods. Though turkey may get the spotlight, and pumpkins are nearly ubiquitous in decor, there is a lot to be learned about the humble potato, the foundation of many wonderful Thanksgiving dishes.

The first thing to know is that potatoes, yams, and sweet potatoes are three different species, and not closely related. We tend to group them together because they are all tubers, a plant structure that stores energy underground. Tubers are a fairly common feature of plants, and though they might share similar properties, this is due to shared function rather than relatedness.

The potato has its origin in the Americas, and is a member of the genus Solanum, part of the widespread and diverse nightshade family. There are around 1,500 different species of nightshade, and they can be found on every continent except Antarctica. Some of these species are important food crops, like tomatoes, eggplants, and potatoes, but many more of its members are vividly poisonous. Nightshades produce toxic alkaloids as a chemical defense against herbivory, and these compounds can be harmful or even lethal to humans that consume them.

Wild potatoes naturally produce an alkaloid called solanine. Solanine makes people sick if they don’t consume much of it, and can kill them if they eat too much. Do domesticated potatoes still contain solanine? That’s a complicated question, and deeply tied to their fascinating history.

Chuño, a traditional preparation of potatoes made in the high Andes. Image by Eric in SF.

Scientists aren’t quite sure which of the many species of wild potato gave rise to the ones on our plates, but think the initial domestication event was between 8,000 - 10,000 years ago in the mountainous regions of southern Peru.

The earliest wild potato pioneers would have needed to find a way to neutralize their toxins, and solanine isn’t destroyed by cooking. What does tame solanine is clay. In the wild, guanaco and vicuna (relatives of the alpaca and llama) eat clay prior to eating wild potatoes. Solanine adsorbs to clay particles, which lets it be transported out of the body through the digestive tract. People may have noticed this behavior and begun to experiment with culinary clay themselves.

Solanine in potatoes can be rendered harmless either by soaking in a clay mixture, or by consuming clay alongside them. Thousands of years of selective breeding in the Andes mountain range developed potatoes with a low enough solanine content that they could be safely eaten without such worries, but there are many cultivars today that still have enough toxins that the traditional methods of preparation are still in use. Modern people living in the Andean highlands eat special clay with their potatoes, and use the clay to treat ailments like ulcers and indigestion as well.

Another way to make toxic potatoes safe which may have been used by early Andean inhabitants is dehydration. Today, one of the traditional Bolivian methods to dehydrate potatoes is natural freeze drying. Potatoes are left outside overnight to freeze, and then the cold dry air of the day carries away moisture. This process is repeated until only a small amount of moisture remains, at which point the potatoes are mashed and then left out to dry again. The resulting product is highly stable and can last years. This potato product is known as chuño, and it is an essential ingredient in many traditional Andean cuisines.

The Andes were home to many different groups of people throughout the past ten thousand years, all of which benefited from the nutrition-dense potato. Thousands of potato cultivars were developed and grown during this era. Some potatoes were better for high altitudes, some for low. Some were better for one style of cooking, while some favored another.

Potato varieties in a Peruvian market. Image by Thayne Tuason.

The harsh climate of the Andes required adaptation and flexibility, and having a multitude of potatoes gave them unprecedented food security and defense against scarcity. They were packed with calories and nutrition, and an easily source of portable food for journeys. They could be stored away for years after harvest too.

For a long time, potatoes were primarily cultivated only within these regions of South America. However, this would not last forever. When the Spaniards reached the New World in the 16th century, they quickly began their hunt for treasure. They hauled boatloads of gold and silver back to Europe, but also brought back botanical wonders. One of these wonders was the potato.

For a long time, potatoes were regarded with rank suspicion in Europe, due to their resemblance to dangerous nightshades. Their taste was considered bland and appealing, and consumption was limited. This would change over the course of a few hundred years, by which point potatoes had helped Europe weather famines and gain much-needed food security. By the end of the 18th century, potatoes had proven their worth, and had become the culinary staple they are today.

In the modern age, potatoes are enjoyed worldwide, and yearly production is over 350 million metric tonnes. China currently produces the most potatoes, followed by India. The United States comes in at fifth, with Idaho leading the way in potato farming. The potato has had a long and fruitful history of humanity, starting with hungry people in the Peruvian mountains, and eventually winning over hearts (and tongues!) across the globe.

Potato Fast Facts

Did you know that potatoes are not commercially grown from seed? What we call “seed potatoes” are actually just small pieces of the tuber removed from the mother plant. Potatoes grow small green tomato-like fruit, but the seeds are rarely harvested. Potato plants grown from seed have uncontrolled and often undesirable mixes of traits, while seed potatoes are identical to the parent plant. This process is called vegetative propagation.

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Only a few potato varieties are grown commercially, but exceptional potato diversity still exists where they were originally grown in the Andes. In 1995, a survey revealed that families in a particular Peruvian valley each grew on average about 10.6 different types of potato. The International Potato Center in Peru is dedicated to preserving this potato diversity, and has almost 5,000 potato cultivars in its collection.

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Purple potatoes. Image by Blanka Luppová.

Potatoes come in many colors! Most supermarkets have white, yellow, and russet potatoes available, but potatoes can also come in purple. Purple potatoes have skin that ranges from purple to blue to almost black, and the inner flesh is a vibrant purple that doesn’t fade with cooking. This color comes from the pigment anthocyanin, which also is found in blueberries and eggplants. Anthocyanin is an antioxidant, and the consumption of antioxidants is linked with longer healthier lives.

Kate Dzikiewicz, Science Curatorial Associate