In their insightful article that claims it's cognition all the way down, Levin and Dennett say:
Biology’s next great horizon is to understand cells, tissues and organisms as agents with agendas (even if unthinking ones)
So what is a biological agency? While we can't define our way to biological understanding (agents live in the real world, not in a textbook), definitions help us look in the right direction. Here's a 1recent, influential definition:
"the capacity of living systems at various levels to participate in their own development, maintenance, and function by regulating their structures and activities in response to conditions they encounter."
or more succinctly, biological agency is the capacity of organisms to participate in their continued existence under precarious conditions. Note that there's a hint of circularity in the definition of agency, since "participate" has many of the connotations of agency, and if we try to define "participate," we might end up going back to agency in some form. But the definition is a pointer, and it's pointing towards the fact that living beings are actively modulating their environments in order to flourish and replicate.
Why is this so important? Because agency is to Cognitive Biology, including unicellular cognition, that mind is to cognitive science, i.e., the central topic of investigation and arguably, the next great horizon of all of biology. Towards the beginning of his famous book "What is Life2," Schrodinger states the aim of his investigation:
"I propose to develop first what you might call ‘a naive physicist’s ideas about organisms’, that is, the ideas which might arise in the mind of a physicist who, after having learnt his physics and, more especially, the statistical foundation of his science, begins to think about organisms and about the way they behave and function and who comes to ask himself conscientiously whether he, from what he has learnt, from the point of view of his comparatively simple and clear and humble science, can make any relevant contributions to the question."
Now replace physics by cognitive science and statistics by information, and we might be able to restate Schrodinger so:
"I propose to develop first what you might call ‘a naive cognitive scientist's ideas about organisms’, that is, the ideas which might arise in the mind of a cognitive scientist who, after having learnt his cognitive science and, more especially, the informational and computational foundation of his science, begins to think about organisms and about the way they behave and function and who comes to ask himself conscientiously whether he, from what he has learnt, from the point of view of his comparatively simple and clear and humble science, can make any relevant contributions to the question."
Schrodinger was prescient in pointing out that the unit of heredity was likely an aperiodic crystal, which it turned out to be: DNA! We can't yet make such bold claims yet, but we can point to agency as the object of our cognitive investigations.