A new criterion for demarcating life from non-life

Life Is Uncertain: Inherent Variability Exhibited by Organisms, and at Higher Levels of Biological Organization

Organisms act stochastically. A not uncommon view in the ecological literature is that this is mainly due to the observer having insufficient information or a stochastic environment-and not partly because organisms themselves respond with inherent unpredictability. In this study, I compile the evidence that contradicts that view. Organisms generate uncertainty internally, which results in irreducible stochastic responses. I consider why: for instance, stochastic responses are associated with greater adaptability to changing environments and resource availability. Over longer timescales, biologically generated uncertainty influences behavior, evolution, and macroecological processes. Indeed, it could be stated that organisms are systems defined by the internal generation, magnification, and record-keeping of uncertainty as inputs to responses. Important practical implications arise if organisms can indeed be defined by an association with specific classes of inherent uncertainty: not least that isolating those signatures then provides a potential means for detecting life, for considering the forms that life could theoretically take, and for exploring the wider limits to how life might become distributed. These are all fundamental goals in astrobiology.

Does the discovery of the mimivirus call into question attempts to define life?

Despite biology being ‘The study of living organisms’ (Proffitt, 2017), there is no consensus between biologists on the definition of life (Bedau, 2010). Defining life has challenged and divided biologists and philosophers alike ever since Aristotle proposed the first definition. Emerging fields like synthetic biology and exobiology have rekindled attempts at establishing a definition of life for practical purposes. The question presents many challenges with each attempt thus far leading to unintended implications and strong counterexamples. It is an inherently multidisciplinary challenge with each approach giving wildly varying and often irreconcilable definitions. The given definitions of life are numerous with over 300 definitions published in books and journals. The unique characteristics of the mimivirus, discovered in 2003, and later giant viruses, rekindled the discussion in defining life, indicating other complications in a definition.

A Unifying Theory of Biological Function

A new theory that naturalizes biological function is explained and compared with earlier etiological and causal role theories. Etiological (or selected effects) theories explain functions from how they are caused over their evolutionary history. Causal role theories analyze how functional mechanisms serve the current capacities of their containing system. The new proposal unifies the key notions of both kinds of theories, but goes beyond them by explaining how functions in an organism can exist as factors with autonomous causal efficacy. The goal-directedness and normativity of functions exist in this strict sense as well. The theory depends on an internal physiological or neural process that mimics an organism’s fitness, and modulates the organism’s variability accordingly. The structure of the internal process can be subdivided into subprocesses that monitor specific functions in an organism. The theory matches well with each intuition on a previously published list of intuited ideas about biological functions, including intuitions that have posed difficulties for other theories.

Extensive fitness and human cooperation

Evolution depends on the fitness of organisms, the expected rate of reproducing. Directly getting offspring is the most basic form of fitness, but fitness can also be increased indirectly by helping genetically related individuals (such as kin) to increase their fitness. The combined effect is known as inclusive fitness. Here it is argued that a further elaboration of fitness has evolved, particularly in humans. It is called extensive fitness and it incorporates producing organisms that are merely similar in phenotype. The evolvability of this mechanism is illustrated by computations on a simple model combining heredity and behaviour. Phenotypes are driven into the direction of high fitness through a mechanism that involves an internal estimate of fitness, implicitly made within the organism itself. This mechanism has recently been conjectured to be responsible for producing agency and goals. In the model, inclusive and extensive fitness are both implemented by letting fitness increase nonlinearly with the size of subpopulations of similar heredity (for the indirect part of inclusive fitness) and of similar phenotype (for the phenotypic part of extensive fitness). Populations implementing extensive fitness outcompete populations implementing mere inclusive fitness. This occurs because groups with similar phenotype tend to be larger than groups with similar heredity, and fitness increases more when groups are larger. Extensive fitness has two components, a direct component where individuals compete in inducing others to become like them and an indirect component where individuals cooperate and help others who are already similar to them.

The Natural Emergence of (Bio)Semiosic Phenomena

Biological organisms appear to have agency, goals, and meaningful behaviour. One possibility is that this is mere appearance, where such properties are not real, but only 'as if' consequences of the physiological structure of organisms. Another possibility is that these properties are real, as emerging from the organism's structure and from how the organism interacts with its environment. Here I will discuss a recent theory showing that the latter position is most likely correct, and argue that the theory is largely consistent with the basics of the field of biosemiotics. The theory can be represented as a triad that resembles the semiotic triad proposed by Peirce, which connects a sign with its object through a process of interpretation. In the theory presented, the sign is an internalized version of fitness (i.e., expected reproductive rate) which refers to the true fitness through a feedback loop that in effect produces interpretation. The feedback loop entangles deterministic and stochastic forms of causation in such a way that genuine agency, goal-directedness, and their associated meaning emerge. It produces a strong form of emergence not reducible to its constituents. The result is that novel phenomena arise that are real and necessary components for a complete understanding of living organisms.

Active causation and the origin of meaning

Purpose and meaning are necessary concepts for understanding mind and culture, but appear to be absent from the physical world and are not part of the explanatory framework of the natural sciences. Understanding how meaning (in the broad sense of the term) could arise from a physical world has proven to be a tough problem. The basic scheme of Darwinian evolution produces adaptations that only represent apparent ("as if") goals and meaning. Here I use evolutionary models to show that a slight, evolvable extension of the basic scheme is sufficient to produce genuine goals. The extension, targeted modulation of mutation rate, is known to be generally present in biological cells and gives rise to two phenomena that are absent from the non-living world: intrinsic meaning and the ability to initiate goal-directed chains of causation (active causation). The extended scheme accomplishes this by utilizing randomness modulated by a feedback loop that is itself regulated by evolutionary pressure. The mechanism can be extended to behavioural variability as well and thus shows how freedom of behaviour is possible. A further extension to communication suggests that the active exchange of intrinsic meaning between organisms may be the origin of consciousness, which in combination with active causation can provide a physical basis for the phenomenon of free will.