Over the last several decades, pesticides have become a standard feature of agricultural ecology. The complex effects of these substances extend far beyond the crop fields themselves. In a series of recent studies, Dr. Jessica Hua has documented the specific impacts that pesticide application has on the surrounding ecosystem. These studies don’t just highlight the interconnected causal web of aquatic ecology, they also offer insight into one of the deepest of evolutionary questions: How does the ability to evolve, evolve? That is, how do genuinely new traits come into being?
The origins of evolutionary creativity remain mysterious, but we can begin to understand them by examining a phenomenon called plasticity. Like the plastic it is named for, plasticity refers to features of organisms that are moldable, flexible, features that change based on the environment.
The specific plastic response that Dr. Hua has been investigating is pesticide resistance. After an initial exposure to pesticide, woodfrogs (Lithobates sylvaticus) will plastically develop pesticide resistance. This doesn’t involve changing their genomes in any way, just their physiology (not unlike how an experienced guitar player developing calluses after prolonged exposure to guitar strings).
This on its own is not terribly interesting – bodies adapt in response to environmental stress across all the branches of life. But what’s notable is that certain populations of frogs that have been consistently exposed to pesticide, over several generations, have been shown to evolve innate resistance. Which is to say that what was once a plastic, flexible physiological change can become a genetically coded trait.
What this means is that a new character was added to the frogs whose origin wasn’t originally a genetic mutation, but rather an active, real time response to the environment. This calls into question the widely believed idea that novel adaptations must originate in the germ line.
This video describes Dr. Hua’s work in more detail
More generally, these findings shed some weak light on the nature of creativity itself. It remains an open biological question to what extent creatures are actively, causally involved in generating their own bodies, and their own evolutionary histories. It is tempting to try to segregate our ideas about organism development into two distinct realms: over here we have the DNA instructions, and over there we have the organism products, and the DNA causes the organisms, and not the other way around. But examples of plasticity like this indicate that relationship between the two is not simply unidirectional. Very often, organisms play an active role in structuring the DNA which makes them.
If you’d like to learn more about Dr. Hua’s work, you can check out this lecture she gave for the EvoS Seminar Series:
Even more information can be found in the papers cited in these videos:
The EvoS Seminar Series is an online class which seeks to provide the public with many links on the chain which connects science to story. We post articles, live lectures, and explainer videos which all present the same ideas from different perspectives and different levels of complexity.