In the preface of his book, A Genetic Switch, famed molecular biologist Mark Ptashne writes regarding his beloved virus, named lambda, “The lambda life cycle is a paradigm for this problem: the virus chooses one or another mode of growth depending upon extracellular signals, and we understand in considerable detail the molecular interactions that mediate these processes.” He is certainly correct that the molecular biology of the viral “decision” is well characterized. Ptashne first described the system in the 1970s, and today it is among the most studied molecular switches in biology. But even in the preface to this scientific text, Ptashne can scarcely avoid agential language when describing the virus, writing, “The virus chooses one or another mode of growth.”
Wait, the virus chooses?
What is striking about the lambda phage, a simple virus that infects E. coli, is that both levels of explanation seem to be true. The molecular explanation for the viral “decision” of which lifecycle to follow is robust and complete. The biochemistry of the system is understood in rich detail to the point that the molecular biology of lambda is a template for scientific understanding of gene regulation in more complex organisms. When lambda infects an E. coli it can either begin to reproduce immediately, killing the cell before it escapes to infect other E. coli in the area, or it can incorporate its viral genome into the DNA of its host and remain there silent for generations.
Which lifecycle the virus “chooses” depends on the health of the E. coli, the number of viruses in the environment, the size of the bacterial community, and the activity of a small number of DNA binding proteins. In other words, lambda chooses how to live based on interactions between its biochemistry and its surrounding environment.
The biology of decision making has been studied in neurons, insects, fish, primates, and in humans of every age. In every example but the last, we assume that a biochemical explanation for behavior is the only explanation necessary. But I suspect that other true explanations for behavior are possible not only in human beings but in every other example, down to the simple lambda phage.
When teaching lambda in my classes it is nearly impossible to escape language that suggest the virus is a decision-making agent, especially considering the effectiveness of an agential explanation. If instead of considering the biochemistry of the decision we instead imagine the virus as carrying out goal seeking activity wherein the virus “desires” to reproduce effectively, we would accurately predict the behavior of the virus in every condition. The activity of the genetic switch that controls lambda is completely understood, but to suggest that a biochemical explanation precludes any other type of explanation is a philosophical decision not inherent to the action of the virus.
As a people, scientist are reticent to use teleological language despite the work of philosopher of science Michael Ruse and many others who have spent careers trying to get us to grow in this area. Biologists in particular are trained not to anthropomorphize our subjects lest the behaviors, motivations, and activity we describe might only be those that we imagine.
But as Christians studying science, I think we have good reasons to reject a reductionism that suggests biochemistry can explain all biology or biology can explain all psychology. I confess that I worry about the precedent set by declaring that lambda behavior is ‘only biochemistry and environment’ just because we can explain it in those terms. What happens if someday ‘biochemistry and environment’ is able to explain my behavior? Would I no longer be a decision-making agent?
Now, to be clear, I do not think the virus is a decision-making agent in the same way that I am a decision-making agent. But I wonder if we can make space to allow the virus to actually make decision. Can I boldly tell my students that “the virus chooses the lytic lifecycle because there are many other E. coli around to infect?”
Even typing it makes me nervous.
I really believe that as humans we use our God given gifts to respond intelligently in human-like ways to our environment and make choices that are for our good. I wonder if maybe flies are able to use their God given gifts to respond intelligently in fly-like ways to their environment and make choices for their good. Or even, maybe viruses use their God given gifts to respond intelligently in virus-like ways to their environment and make choices that are for their good. In that sense, lambda chooses which way to live.
Our explanations for those choices might come from psychology, biology, or biochemistry but each creature is still making a choice.
Christians are typically comfortable having multiple explanations for one event. It comes from our familiarity with dual causality. God delivered the Israelites from Egypt and so did Moses (Exodus 3:8 vs 3:10). God healed the patient and the chemo worked well. God put the rainbow in the sky and water separates the wavelengths of light. We know that God is actually at work in each case. His action is the full explanation for each event. God did it. But Moses, the chemotherapy, and the droplets do something too. The two kinds of explanations are not competitive (as though either God delivered Israel or Moses did) but instead both are true in different ways.
I think there are habits of thought formed by how we interpret the action of little lambda. If I reduce it to biochemistry, then I develop the habit of seeing creatures as “just” something less than they are. In contrast, if I instead recognize lambda as a decision-making agent, then even if I overstate the case, I am learning to see all creatures as active, responsive, and dynamic. Each of these positions habituate my response to the next creature I encounter. Therefore, in an effort to do onto others as I would have them do onto me, I choose to see in the virus a fellow creature making an intelligent choice for its good.
Great essay Clayton- thank you! It reminded me of another essay entitled “True, but not Real” that I suggested to one of my physics classes.
Thanks again! Biology is fascinating!