First Contact and Ethology^{0}

First Contact

It is impossible to pinpoint the exact moment that human beings encountered virtually any animal or plant. Even more difficult is trying to estimate a particular moment when we can say domestication is absolutely occurring or it absolutely is not. To be precise, we must first establish what we mean when we use the word domestication. When most people think of domestication they think of the classic examples of dogs or horses, cows or sheep, goats or pigs. Yet domestication can equally be considered when discussing plants. If domestication involves a mutual benefit arrangement, as espoused by Melidna Zeder, then any plant that achieved more success in reproducing or proliferating while at the same time allowing humans to benefit (usually observed through increased calorie intake and/or population growth) would certainly be considered domesticated.[1] Zeder herself appears to take it almost for granted that plants deserve to fall under the umbrella of domestication, stating: “all considerations of domestication, whether focusing on crops or livestock, acknowledge that it involves a two-way relationship between humans and target plant or animal populations.”[2]

If we accept that both plants and animals can be domesticated, then there is very little logical reason to exclude fungi. Fungi are neither plants nor animals, but they certainly have fulfilled very specific purposes in the history of mankind. In addition to serving as a direct food source (such as wild mushrooms), fungi (specifically yeast) are crucial to the production of bread and beer or wine. Those three manufactured foods greatly impacted human civilizations and gave enormous benefits to the cultures that generated them. On the other end of the partnership, yeasts were able to flourish and spread throughout the world due to the human technological interchange and eventual dependence on bread, beer, and wine.

While yeast are clearly domesticated, their inclusion into the kingdom of Fungi make them neither plants nor animals. However, I would argue that they share enough similarities with animals to render the question of their physiological classification irrelevant. Animals are defined as having six characteristics: they are eukaryotic, multicellular, heterotrophic, motile, respond to external stimuli, have an embryo that go through a blastula stage, and lack a cell wall.[6] Yeast are also eukaryotic and respond to stimuli (through undergoing certain biochemical pathways rather than others). While yeast do contain cell walls and lack embryos, they are heterotrophic and can be compared to animals such as coral in the area of motility. Autotrophic means that an organism produces its own energy, such as plants do through photosynthesis. Heterotrophic means that an organism is dependent on an outside source for its energy. Yeast do not produce their own energy, they are dependent on other organisms for their nutrients. In domesticated yeast the energy required to sustain their life cycles is provided in the glucose found in other organisms (like the grapes collected by man). Coral are classified as animals, yet after their larval stage they settle into one spot and become sessile (non-moving).[7] Finally, though yeast are single celled organisms, they can form multicellular regions known as pseudohyphae (see Evolutionary History).

The original classification system for life on earth was originally devised by Aristotle and then later revised by the scientist Carl Linnaeus. With the recent advancements in genetic technologies, there have been pushed towards reclassification of organisms according to their cytological similarities and differences. Many argue that several of the original criteria for classification should be discarded in favor of analysis of organisms’ genomes.[8] Examining the DNA of plants, yeast, and animals, scientists discovered that yeasts are far more closely related to animals than to plants.[9] A simplified phylogenetic tree for the three kingdoms would look like the following:[10]

Once we’ve established that fungi can indeed fall under the umbrella of domestication, the crucial question becomes how to define when they were initially domesticated. Unlike plants like corn or animals like the horse, yeast is microscopic, and thus unable to be seen until the invention of the microscope by Anton van Leeuwenhoek in the seventeenth century.[3] Without being able to see an organism, how could humans possibly intend to domesticate it? I would argue that intent to domesticate is unnecessary for domestication to occur. Though there are numerous theories to explain the domestication of wolves into dogs (or rather their common ancestor to dogs), a prevailing opinion states that wolves might have become accidentally domesticated through their potential to feed off the fringes off human settlements. Zeder terms this pathway of domestication the commensal pathway and gives numerous examples (all animal) to explain it.[4] Such a pathway would not require a directed imperative to domesticate wolves, instead relying on almost accidental initial domestication followed by directed domestication as time went on.

Following such reasoning I believe that yeast were, if not commensally domesticated, at least accidentally domesticated. When yeasts first became used for the creation of bread and beer, the people at the time did not know precisely what was responsible for their technological leaps. Yet they clearly understood enough to create entire industries centered on yeast metabolism, and understood that there was something important happening when they transferred old bread dough to new, or left their initial dough outside for a time.[5] Over time, humans and yeast became mutually dependent upon one another. Bread and brewing gave mankind a high calorie food and sterilized drink, and yeasts that tended to result in better bread or brews were inadvertently selected for and their lineages propagated.

After the discovery that yeast was directly responsible for fermentation following the work of Louis Pasteur in the nineteenth century, domestication of yeast changed from accidental to purposeful. Strains of yeast were quickly selected for higher fermentation rates, better tasting beers, and superior growing factors.[11] Once yeast became utilized as a model organism for biological studies, strains were cultivated for their physiological relevance or semblance to pertinent human biological phenomenon. With the advent of genetic manipulation in the second half of the twentieth century, new strains of yeast could be created overnight, and thousands of genetic changes per day led to incalculable to strains of yeast across the globe.[12] It can be assured that wherever mankind goes in the future, yeast will follow and flourish.