Are humans smarter than yeast? This question, once posed in jest, is increasingly asked in earnest by those concerned about population growth and diminishing natural resources. It’s the title of an eight minute YouTube video by Dan Chay, but Dave Bice explains its meaning more concisely: “Yeast growing in grape juice provide a good example of overshoot and collapse behavior. The yeast go after the sugar in the juice and in the process of metabolizing that sugar, they produce alcohol and carbon dioxide. As they consume the sugar, they also reproduce and their reproductive rate is dependent on the availability of food. Within a few days, at room temperature, the yeast population soars and the juice is bubbling from the release of so much CO2. But, the alcohol is a pollutant as far as the yeast are concerned and as their population rises, so does the level of alcohol. If there is enough sugar in the juice, the yeast will eventually produce so much alcohol that they start to die off rapidly and as the sugar reservoir is depleted, their reproductive rates plummet, leading to a total collapse of the population. So, in turning the juice into wine, the gluttonous, know-no-restraint yeast do themselves in.”

Dr. Bice is on the faculty of Penn State University. He offers the above as one of his “General Models of Population Dynamics.” He describes other models in which population and resources are balanced and stable, but the “Overshoot and Collapse” model seems to best represent human civilization. Although Dr. Bice teaches earth sciences, he includes population dynamics because “the growing human population is the root cause of all the environmental problems — if we care about the future well-being of our planet and our environment, we cannot ignore the dynamics of the human population. To worry about environmental problems while ignoring the population problem is like treating the symptoms of a disease without ever trying to find a cure. This disease that is population growth has the potential to make our future a very unpleasant one.”

We live on a small planet with limited resources. Our population has more than tripled, from just over two billion to nearly seven billion, in the average lifespan of one individual, about 65 years. During that period we have severely depleted natural resources, befouled the air, contaminated the water, and otherwise exhausted and despoiled the ecosystem on which we depend for life. So I ask again, are humans smarter than yeast?