Introduction
Systems Biology was first proposed in 1998.
In recent years, I feel that the concept of systems biology has gradually gained acceptance.
For an excellent and very accessible overview of systems biology, see Tetsuya J. Kobayashi’s article “What exactly was systems biology?“.
I apologize if I am mistaken, but if systems biology had to be summed up in a single phrase, it would be “understanding life as a system.”
My sense is that this introduced a new perspective across biology as a whole, and particularly into a wide range of fields such as molecular biology, developmental biology, and chronobiology.
I myself work in neuroethology, or more broadly in the study of behavior.
In recent years, neuroethology has also seen a broad wave of computational work that treats animals as systems, including neural simulations, connectome data analysis, and machine learning tools for analyzing animal behavior.
Honestly, I do not know whether these developments in neuroethology were anticipated when systems biology was first proposed, or whether the current situation falls within the scope of Systems Ethology.
Even so, it is a fact that this trend is advancing in neuroethology as well, and in that sense the proposal of systems biology feels remarkably prescient.
The beginnings of Systems Ethology
One question that naturally arises is this: if the current trends in behavioral research are already being absorbed into systems biology, why bother coining a separate term like Systems Ethology?
That’s a fair point, and I do think so myself. But there is a background that led me to deliberately propose Systems Ethology anyway.
This comes largely from a personal wish of mine: I wanted a place where researchers who study behavior could come together.
Behavioral research today is pursued from a wide variety of perspectives. It spans the goal of neuroethology—understanding how neural circuits control behavior—as well as the ecological question of what function a behavior serves in its environment, the evolutionary question of how a behavior evolved, and the information-science question of what strategy and what kind of system underlie a behavior. Behavior is being studied across disciplinary boundaries.
Within neuroethology itself, the range is broad as well, from circuit-level work using model organisms such as fruit flies and mice to studies of unique behavioral mechanisms in non-model organisms, and the field goes by different names such as neuroethology or behavioral neurobiology.
Compounding this, the approaches used to study behavior have also diversified: genetic manipulation of neural activity, recording of neural activity by electrophysiology and calcium imaging, behavioral quantification with machine learning, mathematical descriptions of behavior and the search for behavioral strategies via reinforcement learning, and more classical, detailed observation of behavior. These approaches, too, cross disciplinary boundaries.
As a result, my personal impression is that people attend whichever conference is closest to the scope of their own research, and somewhere along the way I found myself wondering: wait, where is my home conference?
Behavioral research is being pursued from increasingly diverse perspectives, and as things stand it is quite possible to want to learn about a given research method yet have no way to do so.
It struck me as a real missed opportunity, and I imagined that if there were a venue where all of these people gathered in one place, behavioral research might advance further. That was the intention behind creating such a venue.
This is purely my own view, and I do not assume that everyone who has been collaborating with me shares the same motivation, nor that this rests on my own agenda alone. But the desire for a place where everyone could gather was something I heard repeatedly in conversations with various people at conferences.
And so, with the aim of creating such a venue, I set out to propose Systems Ethology. In September 2024, at SWARM2024, I
Toward Understanding the Principles of Animal Behaviors: Systems Ethology
Hayato M Yamanouchi, Yusuke Notomi, Ryoya Tanaka, Shumpei Hisamoto, Shigeto Dobata
submitted the following paper,
Systems Ethology: Toward Elucidating the Design Principles of Animal Behavior
and organized the following session.
Below is the abstract of this organized session, quoted from the SWARM2024 website.
The exploration of biology plays a crucial role in elucidating the behavioral mechanisms of individual agents and their collective behavior as swarms, owing to the complex and diverse nature of animal behavior. In particular, recent remarkable advances in information processing technology have helped to elucidate their complex behavioral patterns. Furthermore, these technological innovations also enable detailed investigations into non-model species where established research tools are lacking, thereby contributing to a broader understanding of various biological phenomena.
Currently, methods for animal behavior analysis are highly diversified, necessitating opportunities for integrated discussions where specialists with cutting-edge knowledge can share their techniques. We therefore propose a framework called “Systems Ethology” to elucidate the design principles of animal behavior. With the overarching goal of understanding animal behavior as a system, we aim to facilitate the exchange of information regarding various approaches to elucidating the mechanisms underlying each behavior. Such cross-disciplinary interactions among researchers can assist in performing more efficient and meaningful research.
In this session, we aim to gather biological insights from various disciplines such as ecology, ethology, and neuroscience. Additionally, proposals for diverse behavioral analysis approaches, incorporating insights from information science and engineering, are also encouraged.
For this session we invited researchers who study behavior from a variety of perspectives, and we were able to put together a very well-attended and lively organized session.
At present, I am exploring whether we can realize a long-held wish of mine: launching a Systems Ethology study group.
The ideas behind Systems Ethology
Next, I would like to discuss what Systems Ethology actually is and how I define it as a discipline.
Ethology has long centered on “Tinbergen’s four questions,” proposed by Niko Tinbergen.
There are various ways of phrasing and framing them, but here I will take the four perspectives to be “survival value,” “ontogeny,” “evolution,” and “causation.”
Niko Tinbergen argued that behavior must be examined from these four perspectives, and they remain an important guiding framework for ethology today, and by extension for neuroethology.
However, each of these perspectives is currently pursued by research that focuses on it in isolation.
To take clear examples, neuroethology focuses on how neurons control behavior from the standpoint of causation, ecology centers on survival value, and evolutionary biology centers on evolution.
Answering each of these questions matters, but these perspectives have tended to exist in isolation, with whatever fell outside a given focus treated as a black box.
In other words, I feel there has not yet been a discipline that focuses simultaneously on the causation and the survival value of behavior and satisfies both scopes. (At the level of individual studies, of course, work combining these views is becoming more common.)
Truly understanding behavior requires all four perspectives—”survival value,” “ontogeny,” “evolution,” and “causation“—so why have they not been integrated? No one really knows, but one factor is surely that it is hard for researchers in these areas to understand one another.
Put the other way around: why not make mutual understanding possible?
Here, using the notion of a system as a common medium may offer a solution.
That is, if systems can serve as a kind of shared language linking these perspectives, researchers should be able to incorporate one another’s ideas.
Here I define this system as the behavioral system.
There are many ways of conceptualizing behavior, and no single definition fits them all, but for simplicity I define behavior here as follows:
The internally coordinated responses (actions or inactions) of whole living organisms (individuals or groups) to internal and/or external stimuli, excluding responses that are more easily understood as developmental changes
Japanese translation: 生物全体（個体または群れ）が内部および／または外部からの刺激に対して内部的に調整した反応（行動または不行動）であり、発達上の変化としてより容易に理解できる反応は除く。
~Source: Levitis et al. (2009)~
That is the definition adopted here.
Recast in systems terms, the output of the system corresponds to behavior.
The part of the system responsible for input and processing is therefore treated as the behavioral system.
A behavioral system can be examined at multiple levels: the individual, the neuron, or the molecule.
Given this diversity of levels, understanding behavior requires working across them and making sense of behavior at several levels at once.
Because this is so complex, however, fully understanding a single system within one study becomes impossible.
That is precisely why we need a venue for sharing diverse approaches and findings across disciplinary boundaries.
Returning to “Tinbergen’s four questions,” Systems Ethology proposes the following four guiding principles for answering them.
1) System structure: Static structure represented by nodes and edges. It includes discovering the behavior and the pathways by which the behavior is formed from inputs. It also elucidates the system’s components and how they are connected.
2) System dynamics: The dynamic structure is represented by nodes and edges. This perspective includes dynamics of the system (structure changes of the systems) and dynamics on the system (inner-statements transition of the nodes in the system). Dynamic system structure changes as a result of learning, development, and other parameters.
3) The control method: Methods for controlling the system’s states and behaviors. This method includes behavioral changes caused by intervention on the system’s nodes or edges.
4) The design method: Meaning and principles of the system. This method includes understanding the system’s adaptive and evolutionary significance.
~Source: Yamanouchi et al. SWARM2024, (2024)~
These principles specify which aspects of a system we set out to elucidate, and they are based on the four principles of systems biology.
No one is certain what the future of Systems Ethology holds, and as things stand the details have yet to be unified.
That is exactly why I want to build Systems Ethology into a forum for thinking about the future of the study of behavior.
The Future of Systems Ethology
At present, Systems Ethology has only been proposed as a new framework, and so far only in a conference paper.
Eventually I hope to present it to a wider audience, for example as an opinion piece in a journal.
My more immediate hope is to realize the original aim: a place where people who study behavior can come together.
As a first step, I would like to organize a Systems Ethology research meeting here in Japan.
Closing Note
This article reflects my own personal views and is not meant to define Systems Ethology definitively.
Please bear in mind that others may see things differently, and that I may well be mistaken on some points.
