Search Our Scientific Publications & Authors

Artif Life 2019 ;25(1):33-49

ProtoLife, Inc.

We detect ongoing innovation in empirical data about human technological innovations. Ongoing technological innovation is a form of open-ended evolution, but it occurs in a nonbiological, cultural population that consists of actual technological innovations that exist in the real world. The change over time of this population of innovations seems to be quite open-ended. Read More

Artif Life 2019 ;25(1):4-8

Binghamton University-SUNY, Department of Systems Sciences and Industrial Engineering.

Open-endedness is often considered a prerequisite property of the whole evolutionary system and its dynamical behaviors. In the actual history of evolution on Earth, however, there are many examples showing that open-endedness is rather a consequence of evolution. We suggest that this view, which we call evolved open-endedness (EOE), be incorporated more into research on open-ended evolution. Read More

Artif Life 2019 ;25(1):22-32

Brandeis University, Department of Computer Science .

The escalation of complexity is a commonly cited benefit of coevolutionary systems, but computational simulations generally fail to demonstrate this capacity to a satisfactory degree. We draw on a macroevolutionary theory of escalation to develop a set of criteria for coevolutionary systems to exhibit escalation of strategic complexity. By expanding on a previously developed model of the evolution of memory length for cooperative strategies by Kristian Lindgren, we resolve previously observed limitations on the escalation of memory length by extending operators of evolutionary variation. Read More

Artif Life 2019 ;25(1):9-21

University of Southern Denmark, Center for Fundamental Living Technology (FLinT), Department for Physics, Chemistry, and Pharmacy.

We document and discuss two different modes of evolution across multiple systems, optimization and expansion. The former suffices in systems whose size and interactions do not change substantially over time, while the latter is a key property of open-ended evolution, where new players and interaction types enter the game. We first investigate systems from physics, biology, and engineering and argue that their evolutionary optimization dynamics is the cumulative effect of multiple independent events, or quakes, which are uniformly distributed on a logarithmic time scale and produce a decelerating fitness improvement when using the appropriate independent variable. Read More

Artif Life 2019 ;25(1):1-3

Monash University.

Nature's spectacular inventiveness, reflected in the enormous diversity of form and function displayed by the biosphere, is a feature of life that distinguishes living most strongly from nonliving. It is, therefore, not surprising that this aspect of life should become a central focus of artificial life. We have known since Darwin that the diversity is produced dynamically, through the process of evolution; this has led life's creative productivity to be called Open-Ended Evolution (OEE) in the field. Read More

Artif Life 2019 ;25(1):74-91

Brandeis University DEMO Lab.

To study open-ended coevolution, we define a complexity metric over interacting finite state machines playing formal language prediction games, and study the dynamics of populations under competitive and cooperative interactions. In the past purely competitive and purely cooperative interactions have been studied extensively, but neither can successfully and continuously drive an arms race. We present quantitative results using this complexity metric and analyze the causes of varying rates of complexity growth across different types of interactions. Read More

Artif Life 2019 ;25(1):50-73

Michigan State University, BEACON Center for the Study of Evolution in Action, Department of Computer Science and Engineering Program in Ecology, Evolutionary Biology, and Behavior.

Building more open-ended evolutionary systems can simultaneously advance our understanding of biology, artificial life, and evolutionary computation. In order to do so, however, we need a way to determine when we are moving closer to this goal. We propose a set of metrics that allow us to measure a system's ability to produce commonly-agreed-upon hallmarks of open-ended evolution: change potential, novelty potential, complexity potential, and ecological potential. Read More

Artif Life 2018 25;24(4):296-328. Epub 2019 Jan 25.

Michigan State University, BEACON Center for the Study of Evolution in Action, Department of Computer Science and Engineering.

In nature, gene regulatory networks are a key mediator between the information stored in the DNA of living organisms (their genotype) and the structural and behavioral expression this finds in their bodies, surviving in the world (their phenotype). They integrate environmental signals, steer development, buffer stochasticity, and allow evolution to proceed. In engineering, modeling and implementations of artificial gene regulatory networks have been an expanding field of research and development over the past few decades. Read More

Artif Life 2018 25;24(4):250-276. Epub 2019 Jan 25.

Nanjing Agricultural University, Department of Zoology, College of Life Sciences.

Digital evolution is a computer-based instantiation of Darwinian evolution in which short self-replicating computer programs compete, mutate, and evolve. It is an excellent platform for addressing topics in long-term evolution and paleobiology, such as mass extinction and recovery, with experimental evolutionary approaches. We evolved model communities with ecological interdependence among community members, which were subjected to two principal types of mass extinction: a pulse extinction that killed randomly, and a selective press extinction involving an alteration of the abiotic environment to which the communities had to adapt. Read More

Artif Life 2018 25;24(4):277-295. Epub 2019 Jan 25.

Institute of Cognitive Sciences and Technologies, National Research Council.

Previous evolutionary studies demonstrated how robust solutions can be obtained by evaluating agents multiple times in variable environmental conditions. Here we demonstrate how agents evolved in environments that vary across generations outperform agents evolved in environments that remain fixed. Moreover, we demonstrate that best performance is obtained when the environment varies at a moderate rate across generations, that is, when the environment does not vary every generation but every N generations. Read More

Artif Life 2018 25;24(4):229-249. Epub 2019 Jan 25.

Michigan State University.

Mutualisms occur when at least two species provide a net fitness benefit to each other. These types of interactions are ubiquitous in nature, with more being discovered regularly. Mutualisms are vital to humankind: Pollinators and soil microbes are critical in agriculture, bacterial microbiomes regulate our health, and domesticated animals provide us with food and companionship. Read More

Artif Life 2018 ;24(3):199-217

Imperial College London.

One important sense of the term "adaptation" is the process by which an agent changes appropriately in response to new information provided by environmental stimuli. We propose a novel quantitative measure of this phenomenon, which extends a little-known definition of adaptation as "increased robustness to repeated perturbation" proposed by Klyubin (2002). Our proposed definition essentially corresponds to the average value (relative to some fitness function) of state changes that are caused by the environment (in some statistical ensemble of environments). Read More

Artif Life 2018 ;24(3):182-198

Imperial College London.

The idea that an agent's actions can impact its actual long-term survival is a very appealing one, underlying influential treatments such as Di Paolo's (2005). However, this presents a tension with understanding the agent and environment as possessing specific objective physical microstates. More specifically, we show that such an approach leads to undesirable outcomes, for example, all organisms being maladaptive on average. Read More

Artif Life 2018 ;24(3):220-223

University of Glasgow, MRC/CSO Social and Public Health Sciences Unit.

Despite tremendous advancements in population health in recent history, human society currently faces significant challenges from wicked health problems. These are problems where the causal mechanisms at play are obscured and difficult to address, and consequently they have defied efforts to develop effective interventions and policy solutions using traditional population health methods. Systems-based perspectives are vital to the development of effective policy solutions to seemingly intractable health problems like obesity and population aging. Read More

Artif Life 2018 ;24(3):227

Artif Life 2018 ;24(3):218-219

University of Surrey, Centre for Research in Social Simulation (CRESS), Centre for Evaluation of Complexity Across the Nexus (CECAN).

Artif Life 2018 ;24(3):157-181

University of Wyoming, Department of Computer Science, Evolving AI Lab.

Many believe that an essential component for the discovery of the tremendous diversity in natural organisms was the evolution of evolvability, whereby evolution speeds up its ability to innovate by generating a more adaptive pool of offspring. One hypothesized mechanism for evolvability is developmental canalization, wherein certain dimensions of variation become more likely to be traversed and others are prevented from being explored (e.g. Read More

Artif Life 2018 17;24(2):154-156. Epub 2018 Apr 17.

Language Acquisition and Language Processing Lab, Department of Language and Literature, Norwegian University of Science and Technology.

In their commentary on our work, Ravignani and Verhoef (2018) raise concerns about two methodological aspects of our experimental paradigm (the signaling game): (1) the use of melodic signals of fixed length and duration, and (2) the fact that signals are endowed with meaning. They argue that music is hardly a semantic system and that our methodological choices may limit the capacity of our paradigm to shed light on the emergence and evolution of a number of putative musical universals. We reply that musical systems are semantic systems and that the aim of our research is not to study musical universals as such, but to compare more closely the kinds of principles that organize meaning and structure in linguistic and musical systems. Read More

Artif Life 2018 17;24(2):106-118. Epub 2018 Apr 17.

Department of Earth and Planetary Sciences, Harvard University; and Santa Fe Institute.

Life and other dissipative structures involve nonlinear dynamics that are not amenable to conventional analysis. Advances are being made in theory, modeling, and simulation techniques, but we do not have general principles for designing, controlling, stabilizing, or eliminating these systems. There is thus a need for tools that can transform high-level descriptions of these systems into useful guidance for their modification and design. Read More

Artif Life 2018 17;24(2):149-153. Epub 2018 Apr 17.

Leiden Institute of Advanced Computer Science (LIACS), Leiden University; and Center for Research in Language, University of California, San Diego.

Music is a peculiar human behavior, yet we still know little as to why and how music emerged. For centuries, the study of music has been the sole prerogative of the humanities. Lately, however, music is being increasingly investigated by psychologists, neuroscientists, biologists, and computer scientists. Read More

Artif Life 2018 17;24(2):119-127. Epub 2018 Apr 17.

Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez.

What is the influence of short-term memory enhancement on the emergence of grammatical agreement systems in multi-agent language games? Agreement systems suppose that at least two words share some features with each other, such as gender, number, or case. Previous work, within the multi-agent language-game framework, has recently proposed models stressing the hypothesis that the emergence of a grammatical agreement system arises from the minimization of semantic ambiguity. On the other hand, neurobiological evidence argues for the hypothesis that language evolution has mainly related to an increasing of short-term memory capacity, which has allowed the online manipulation of words and meanings participating particularly in grammatical agreement systems. Read More

Artif Life 2018 17;24(2):128-148. Epub 2018 Apr 17.

Smart Data Research Group, SW-Content Research Laboratory, Electronics & Telecommunications Research Institute (ETRI).

Artificial life (ALife) examines systems related to natural life, its processes, and its evolution, using simulations with computer models, robotics, and biochemistry. In this article, we focus on the computer modeling, or "soft," aspects of ALife and prepare a framework for scientists and modelers to be able to support such experiments. The framework is designed and built to be a parallel as well as distributed agent-based modeling environment, and does not require end users to have expertise in parallel or distributed computing. Read More

Artif Life 2018 17;24(2):85-105. Epub 2018 Apr 17.

Department of Systems Science and Industrial Engineering, Center for Collective Dynamics of Complex Systems, Binghamton University. (HS).

Whereas the relationship between criticality of gene regulatory networks (GRNs) and dynamics of GRNs at a single-cell level has been vigorously studied, the relationship between the criticality of GRNs and system properties at a higher level has not been fully explored. Here we aim at revealing a potential role of criticality of GRNs in morphogenesis, which is hard to uncover through the single-cell-level studies, especially from an evolutionary viewpoint. Our model simulated the growth of a cell population from a single seed cell. Read More

Artif Life 2018 25;24(1):5-9. Epub 2018 Jan 25.

University of California, Merced.

We describe the questions and discussions raised at the First Workshop on Social Learning and Cultural Evolution held at theArtificial Life Conference 2016 in Cancún, Mexico in July 2016. The purpose of the workshop was to assemble artificial life researchers interested in social learning and cultural evolution into one group so that we could focus on recent work and interesting open questions. Our discussion related to both the mechanisms of social learning and cultural evolution and the consequences and influence of social learning and cultural evolution on living systems. Read More

Artif Life 2018 25;24(1):10-28. Epub 2018 Jan 25.

School of Computing, Edinburgh Napier University. E-mail:

Artificial life is concerned with understanding the dynamics of human societies. A defining feature of any society is its institutions. However, defining exactly what an institution is has proven difficult, with authors often talking past each other. Read More

Artif Life 2018 25;24(1):29-48. Epub 2018 Jan 25.

Evolutionary and Adaptive Systems Group, University of Sussex. E-mail:

In both social systems and ecosystems there is a need to resolve potential conflicts between the interests of individuals and the collective interest of the community. The collective interests need to survive the turbulent dynamics of social and ecological interactions. To see how different systems with different sets of interactions have different degrees of robustness, we need to look at their different contingent histories. Read More

Artif Life 2018 25;24(1):1-4. Epub 2018 Jan 25.

Cognitive Science Program, Indiana University, Bloomington, Indiana, USA.

Artif Life 2018 25;24(1):80-84. Epub 2018 Jan 25.

Centre for Research in Social Simulation (CRESS), Centre for Evaluation of Complexity Across the Nexus (CECAN), University of Surrey, UK. E-mail:

Artif Life 2018 25;24(1):49-55. Epub 2018 Jan 25.

Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, 2-12-1-IE-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan. E-mail:

This is a report on the Biological Foundations of Enactivism Workshop, which was held as part of Artificial Life XV. The workshop aimed to revisit enactivism's contributions to biology and to revitalize the discussion of autonomy with the goal of grounding it in quantitative definitions based in observable phenomena. This report summarizes some of the important issues addressed in the workshop's talks and discussions, which include how to identify emergent individuals out of an environmental background, what the roles of autonomy and normativity are in biological theory, how new autonomous agents can spontaneously emerge at the origins of life, and what science can say about subjective experience. Read More

Artif Life 2018 25;24(1):56-70. Epub 2018 Jan 25.

Algorithmic Dynamics Lab, Unit of Computational Medicine, SciLifeLab, Karolinska Institute, Karolinska Hospital L8:05, SE-171 76, Stockholm, Sweden. E-mail:

Is undecidability a requirement for open-ended evolution (OEE)? Using methods derived from algorithmic complexity theory, we propose robust computational definitions of open-ended evolution and the adaptability of computable dynamical systems. Within this framework, we show that decidability imposes absolute limits on the stable growth of complexity in computable dynamical systems. Conversely, systems that exhibit (strong) open-ended evolution must be undecidable, establishing undecidability as a requirement for such systems. Read More

Artif Life 2018 25;24(1):71-79. Epub 2018 Jan 25.

Chemical Robotics Laboratory, University of Chemistry and Technology Prague, Technická 3, Prague 6, 166 28, Czech Republic. E-mail:

Protocells are objects that mimic one or several functions of biological cells and may be embodied as solid particles, lipid vesicles, or droplets. Our work is based on using decanol droplets in an aqueous solution of sodium decanoate in the presence of salt. A decanol droplet under such conditions bears many qualitative similarities with living cells, such as the ability to move chemotactically, divide and fuse, or change its shape. Read More

Artif Life 2017 6;23(4):453-480. Epub 2017 Oct 6.

École Polytechnique.

One proposed scenario for the emergence of biochemical oscillations is that they may have provided the basic mechanism behind cellular self-replication by growth and division. However, alternative scenarios not requiring any chemical oscillation have also been proposed. Each of the various protocell models proposed to support one or another scenario comes with its own set of specific assumptions, which makes it difficult to ascertain whether chemical oscillations are required or not for cellular self-replication. Read More

Artif Life 2017 6;23(4):552-557. Epub 2017 Oct 6.

University of Southern Denmark Santa Fe Institute.

We summarize the results and perspectives from a companion article, where we presented and evaluated an alternative architecture for data storage in distributed networks. We name the bio-inspired architecture RAIN, and it offers file storage service that, in contrast with current centralized cloud storage, has privacy by design, is open source, is more secure, is scalable, is more sustainable, has community ownership, is inexpensive, and is potentially faster, more efficient, and more reliable. We propose that a RAIN-style architecture could form the backbone of the Internet of Things that likely will integrate multiple current and future infrastructures ranging from online services and cryptocurrency to parts of government administration. Read More

Artif Life 2017 6;23(4):550-551. Epub 2017 Oct 6.

University of Surrey.

Artif Life 2017 6;23(4):481-492. Epub 2017 Oct 6.

University of the West of England.

This article suggests that the fundamental haploid-diploid cycle of eukaryotic sex exploits a rudimentary form of the Baldwin effect. With this explanation for the basic cycle, the other associated phenomena can be explained as evolution tuning the amount and frequency of learning experienced by an organism. Using the well-known NK model of fitness landscapes, it is shown that varying landscape ruggedness varies the benefit of the haploid-diploid cycle, whether based upon endomitosis or syngamy. Read More

Artif Life 2017 6;23(4):528-549. Epub 2017 Oct 6.

University of Chemistry and Technology Prague.

Liquid droplets are very simple objects present in our everyday life. They are extremely important for many natural phenomena as well as for a broad variety of industrial processes. The conventional research areas in which the droplets are studied include physical chemistry, fluid mechanics, chemical engineering, materials science, and micro- and nanotechnology. Read More

Artif Life 2017 6;23(4):493-517. Epub 2017 Oct 6.

University of Bristol.

Social learning, defined as the imitation of behaviors performed by others, is recognized as a distinctive characteristic in humans and several other animal species. Previous work has claimed that the evolutionary fixation of social learning requires decision-making cognitive abilities that result in transmission bias (e.g. Read More

Artif Life 2017 6;23(4):518-527. Epub 2017 Oct 6.

University Erlangen-Nuremberg.

In Lévy walks (LWs), particles move with a fixed speed along straight line segments and turn in new directions after random time intervals that are distributed according to a power law. Such LWs are thought to be an advantageous foraging and search strategy for organisms. While complex nervous systems are certainly capable of producing such behavior, it is not clear at present how single-cell organisms can generate the long-term correlated control signals required for a LW. Read More

Artif Life 2017 ;23(3):424-448

Moffitt Cancer Center.

The importance of individual cells in a developing multicellular organism is well known, but precisely how the individual cellular characteristics of those cells collectively drive the emergence of robust, homeostatic structures is less well understood. For example, cell communication via a diffusible factor allows for information to travel across large distances within the population, and cell polarization makes it possible to form structures with a particular orientation, but how do these processes interact to produce a more robust and regulated structure? In this study we investigate the ability of cells with different cellular characteristics to grow and maintain homeostatic structures. We do this in the context of an individual-based model where cell behavior is driven by an intracellular network that determines the cell phenotype. Read More

Artif Life 2017 ;23(3):343-350

Augmanity.

Asimov's three laws of robotics, which were shaped in the literary work of Isaac Asimov (1920-1992) and others, define a crucial code of behavior that fictional autonomous robots must obey as a condition for their integration into human society. While, general implementation of these laws in robots is widely considered impractical, limited-scope versions have been demonstrated and have proven useful in spurring scientific debate on aspects of safety and autonomy in robots and intelligent systems. In this work, we use Asimov's laws to examine these notions in molecular robots fabricated from DNA origami. Read More

Artif Life 2017 ;23(3):351-373

University of Vermont.

In some evolutionary robotics experiments, evolved robots are transferred from simulation to reality, while sensor/motor data flows back from reality to improve the next transferral. We envision a generalization of this approach: a simulation-to-reality pipeline. In this pipeline, increasingly embodied agents flow up through a sequence of increasingly physically realistic simulators, while data flows back down to improve the next transferral between neighboring simulators; physical reality is the last link in this chain. Read More

Artif Life 2017 ;23(3):374-405

University of Birmingham.

The idea that lifetime learning can have a significant effect on life history evolution has recently been explored using a series of artificial life simulations. These involved populations of competing individuals evolving by natural selection to learn to perform well on simplified abstract tasks, with the learning consisting of identifying regularities in their environment. In reality, there is more to learning than that type of direct individual experience, because it often includes a substantial degree of social learning that involves various forms of imitation of what other individuals have learned before them. Read More

Artif Life 2017 ;23(3):406-423

SISSA International School for Advanced Studies.

It has been proposed that languages evolve by adapting to the perceptual and cognitive constraints of the human brain, developing, in the course of cultural transmission, structural regularities that maximize or optimize learnability and ease of processing. To what extent would perceptual and cognitive constraints similarly affect the evolution of musical systems? We conducted an experiment on the cultural evolution of artificial melodic systems, using multi-generational signaling games as a laboratory model of cultural transmission. Signaling systems, using five-tone sequences as signals, and basic and compound emotions as meanings, were transmitted from senders to receivers along diffusion chains in which the receiver in each game became the sender in the next game. Read More

Artif Life 2017 ;23(3):295-317

University of New Mexico.

Inspired by natural biochemicals that perform complex information processing within living cells, we design and simulate a chemically implemented feedforward neural network, which learns by a novel chemical-reaction-based analogue of backpropagation. Our network is implemented in a simulated chemical system, where individual neurons are separated from each other by semipermeable cell-like membranes. Our compartmentalized, modular design allows a variety of network topologies to be constructed from the same building blocks. Read More

Artif Life 2017 ;23(3):318-342

Icahn School of Medicine at Mount Sinai.

Amoeba, a computer platform inspired by the Tierra system, is designed to study the generation of self-replicating sequences of machine operations (opcodes) from a prebiotic world initially populated by randomly selected opcodes. Point mutations drive opcode sequences to become more fit as they compete for memory and CPU time. Significant features of the Amoeba system include the lack of artificial encapsulation (there is no write protection) and a computationally universal opcode basis set. Read More

Artif Life 2017 17;23(2):287-294. Epub 2017 May 17.

Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Avda. Diagonal Las Torres 2640, Peñalolén, Santiago, Chile. E-mail:

Traditionally, the formation of vocabularies has been studied by agent-based models (primarily, the naming game) in which random pairs of agents negotiate word-meaning associations at each discrete time step. This article proposes a first approximation to a novel question: To what extent is the negotiation of word-meaning associations influenced by the order in which agents interact? Automata networks provide the adequate mathematical framework to explore this question. Computer simulations suggest that on two-dimensional lattices the typical features of the formation of word-meaning associations are recovered under random schemes that update small fractions of the population at the same time; by contrast, if larger subsets of the population are updated, a periodic behavior may appear. Read More

Artif Life 2017 17;23(2):169-185. Epub 2017 May 17.

Department of Engineering, Trumpington Street, The University of Cambridge, Cambridge, CB21PZ, UK. E-mail: (A.R.).

Evolutionary algorithms have previously been applied to the design of morphology and control of robots. The design space for such tasks can be very complex, which can prevent evolution from efficiently discovering fit solutions. In this article we introduce an evolutionary-developmental (evo-devo) experiment with real-world robots. Read More

Artif Life 2017 17;23(2):236-286. Epub 2017 May 17.

Perceptual Robots, Windsor SL4 1TB, United Kingdom. E-mail:

Departing from the conventional view of the reasons for the behavior of living systems, this research presents a radical and unique view of that behavior, as the observed side effects of a hierarchical set of simple, continuous, and dynamic negative feedback control systems, by way of an experimental model implemented on a real-world autonomous robotic rover. Rather than generating specific output from input, the systems control their perceptual inputs by varying output. The variables controlled do not exist in the environment, but are entirely internal perceptions constructed as a result of the layout and connections of the neural architecture. Read More

Artif Life 2017 17;23(2):119-123. Epub 2017 May 17.

Vrije Universiteit Amsterdam, Amsterdam, The Netherlands. E-mail:

Artif Life 2017 17;23(2):186-205. Epub 2017 May 17.

Department of Computer Science and Creative Technologies, University of the West of England, Bristol, UK. E-mail: (R.J.P.).

Design mining is the use of computational intelligence techniques to iteratively search and model the attribute space of physical objects evaluated directly through rapid prototyping to meet given objectives. It enables the exploitation of novel materials and processes without formal models or complex simulation. In this article, we focus upon the coevolutionary nature of the design process when it is decomposed into concurrent sub-design-threads due to the overall complexity of the task. Read More