There is no broadly accepted definition of ‘life.’ Suggested definitions face problems, often in the form of robust counter-examples. Here we use insights from philosophical investigations into language to argue that defining ‘life’ currently poses a dilemma analogous to that faced by those hoping to define ‘water’ before the existence of molecular theory. In the absence of an analogous theory of the nature of living systems, interminable controversy over the definition of life is inescapable.

Familiarity with Charles Darwin's treatise on evolution is essential to every well-educated individual. One of the most important books ever published--and a continuing source of controversy, a century and a half later--this classic of science is reproduced in a facsimile of the critically acclaimed first edition.

This collection of revised and new essays argues that biology is an autonomous science rather than a branch of the physical sciences. Ernst Mayr, widely considered the most eminent evolutionary biologist of the 20th century, offers insights on the history of evolutionary thought, critiques the conditions of philosophy to the science of biology, and comments on several of the major developments in evolutionary theory. Notably, Mayr explains that Darwin's theory of evolution is actually five separate theories, each with its own (...) history, trajectory and impact. Ernst Mayr, commonly referred to as the "Darwin of the 20th century" and listed as one of the top 100 scientists of all-time, is Professor Emeritus at Harvard University. What Makes Biology Unique is the 25th book he has written during his long and prolific career. His recent books include This is Biology: The Science of the Living World (Belknap Press, 1997) and What Evolution Is (Basic Books, 2002). (shrink)

To surmount the notorious difficulties of defining life, we should evaluate theories of life not by whether they provide necessary and sufficient conditions for our current preconceptions about life but by how well they explain living phenomena and how satisfactorily they resolve puzzles about life. On these grounds, the theory of life as supple adaptation (Bedau 1996) gets support from its natural and compelling resolutions of the following four puzzles: (1) How are different forms of life at different levels of (...) the vital hierarchy related? (2) Is there a continuum between life and non-life? (3) Does life essentially concern a living entity’s material composition or its form? (4) Are life and mind intrinsically connected? (shrink)

Viruses have generally been thought of as infectious agents. New data on mimivirus, however, suggests a reinterpretation of this thought. Earth’s biosphere seems to contain many more viruses than previously thought and they are relevant in the maintenance of ecosystems and biodiversity. Viruses are not considered to be alive because they are not free-living entities and do not have cellular units. Current hypotheses indicate that some viruses may have been the result of genomic reduction of cellular life forms. However, new (...) studies relating to the origins of biological systems suggest that viruses could also have originated during the transition from First to the Last Universal Common Ancestor. Within this setting, life has been established as chemical informational system and could be interpreted as a macrocode of multiple layers. The first entity to acquire these features was the First Universal Common Ancestor that evolved to an intermediate ancestral that could be named T-LUCA and be equated to Woese’s concept of progenotes. T-LUCA may have remained as undifferentiated subsystems with viruses-like structures. The net result is that both cellular life forms and viruses shared protein synthesis apparatuses. In short, virus is a strategy of life reached by two paths: T-LUCAs like entities and the reduction of cellular life forms. (shrink)

Biosemiotics argues that “sign” and “meaning” are two essential concepts for the explanation of life. Peircean biosemiotics, founded by Tomas Sebeok from Peirce’s semiotics and Jacob von Uexkül’s studies on animal communication, today makes up the mainstream of this discipline. Marcello Barbieri has developed an alternative account of meaning in biology based on the concept of code. Barbieri rejects Peircean biosemiotics on the grounds that this discipline opens the door to nonscientific approaches to biology through its use of the concept (...) of “interpretation.” In this article, it is noted that Barbieri does not adequately distinguish among Peirce’s semiotics, Peircean biosemiotics, and “interpretation-based” biosemiotics. Two key arguments of Barbieri are criticized: his limited view of science and his rejection of “interpretation-based” biosemiotics. My argument is based on tools taken from a different approach: Robert Rosen’s relational biology. Instead of “signs” and “meanings,” the study begins in this case from the “components” and “functions” of the organism. Rosen pursues a new definition of a law of nature, introduces the anticipatory nature of organisms, and defines the living being as a system closed to efficient cause. It is shown that Code Biosemiotics and Peircean biosemiotics can share a common field of study. Additionally, some proposals are suggested to carry out a reading of Rosen’s biology as a biosemiotic theory. (shrink)

The phylogenetic trees reconstructed from molecular data have led to the discovery that all living creatures belong to three primary kingdoms, or domains, because there are three types of cells in nature. The primary kingdoms are referred to as Archaea, Bacteria, and Eukaya, and their first representatives were the first modern cells that appeared on Earth. All known cells, on the other hand, contain a virtually universal genetic code, and this implies that the code evolved in a population of primitive (...) systems that preceded the first modern cells and is collectively known as the common ancestor of all life. This gives us the problem of understanding how the descendants of the common ancestor gave origin to the first modern cells. In this article it is argued that the appearance of the genetic code allowed the ancestral systems to translate genes into specific proteins, but their behavior was still ambiguous because they were unable to produce specific responses to the signals from the environment. To that purpose they needed to evolve signal processing codes, and here it is proposed that the development of these codes was a crucial step in the evolution of the first modern cells. (shrink)

Today there are two major theoretical frameworks in biology. One is the ‘chemical paradigm’, the idea that life is an extremely complex form of chemistry. The other is the ‘information paradigm’, the view that life is not just ‘chemistry’ but ‘chemistry-plus-information’. This implies the existence of a fundamental difference between information and chemistry, a conclusion that is strongly supported by the fact that information and information-based-processes like heredity and natural selection simply do not exist in the world of chemistry. Against (...) this conclusion, the supporters of the chemical paradigm have pointed out that information processes are no different from chemical processes because they are both described by the same physical quantities. They may appear different, but this is only because they take place in extremely complex systems. According to the chemical paradigm, in other words, biological information is but a shortcut term that we use to avoid long descriptions of countless chemical reactions. It is intuitively appealing, but it does not represent a new ontological entity. It is merely a derived construct, a linguistic metaphor. The supporters of the information paradigm insist that information is a real and fundamental entity of Nature, but have not been able to prove this point. The result is that the chemical view has not been abandoned and the two paradigms are both coexisting today. Here it is shown that an alternative does exist and is a third theoretical framework that is referred to as the ‘code paradigm’. The key point is that we need to introduce in biology not only the concept of information but also that of meaning because any code is based on meaning and a genetic code does exist in every cell. The third paradigm is the view that organic information and organic meaning exist in every living system because they are the inevitable results of the processes of copying and coding that produce genes and proteins. Their true nature has eluded us for a long time because they are nominable entities, i.e., objective and reproducible observables that can be described only by naming their components in their natural order. They have also eluded us because nominable entities exist only in artifacts and biologists have not yet come to terms with the idea that life is artifact making. This is the idea that life arose from matter and yet it is fundamentally different from it because inanimate matter is made of spontaneous structures whereas life is made of manufactured objects. It will be shown, furthermore, that the existence of information and meaning in living systems is documented by the standard procedures of science. We do not have to abandon the scientific method in order to introduce meaning in biology. All we need is a science that becomes fully aware of the existence of organic codes in Nature. (shrink)

Ecology is usually described as the study of organisms interacting with one another and their environments. From this view of ecology, viruses – not usually considered to be organisms – would merely be part of the environment. Since the late 1980s, however, a growing stream of micrographic, experimental, molecular, and model-based (theoretical) research has been investigating how and why viruses should be understood as ecological actors of the most important sort. Viruses, especially phage, have been revealed as participants in the (...) planet's most crucial food webs, even though viruses technically consume nothing (they do not metabolize by themselves). Even more impressively, viruses have been identified as regulators of planetary biogeochemistry, in which they control cycles such as carbon, nitrogen and phosphorus – cycles on which all life depends. Although much biogeochemical research black-boxes the entities filling functional roles, it is useful to focus a little more closely to understand how viruses can be held responsible for the global processes of life. This paper will give a brief overview of the history of virus ecology and tease out the implications of large-scale ecological modelling with viruses. This analysis suggests that viruses should be conceptualized as ecological actors that are at least comparable and possibly equal to organismal actors. Ecological agency can therefore be distinguished from standard interpretations of biological agency. (shrink)

All of the attempts to date to find a set of necessary and sufficient conditions for life, in order to provide an essential definition of life, have failed. We only have at our disposal series of lists that contain diverse characteristics usually found in living beings. Some authors have drawn from this fact the conclusion that life is not a natural kind. It will be argued here that this conclusion is too hasty and that if life is understood as a (...) natural kind in the non-essentialist sense of a homeostatic property cluster, it is easy to see why the attempts to find a unique and essentialist definition of life have failed. Understanding life in this way would imply that the pretension to find such a type of definition should be abandoned. (shrink)

The final version of the paper is published pp. 117-166 in: Myrdene Anderson and Floyd Merrell (eds.): On Semiotic Modeling . Mouton de Gruyter, Berlin and New York, 1991.

In The Origin of Species (1859) Darwin challenged many of the most deeply-held beliefs of the Western world. Arguing for a material, not divine, origin of species, he showed that new species are achieved by "natural selection." The Origin communicates the enthusiasm of original thinking in an open, descriptive style, and Darwin's emphasis on the value of diversity speaks more strongly now than ever. As well as a stimulating introduction and detailed notes, this edition offers a register of the many (...) writers referred to by Darwin in the text. (shrink)

Systems Biology and the Modern Synthesis are recent versions of two classical biological paradigms that are known as structuralism and functionalism, or internalism and externalism. According to functionalism (or externalism), living matter is a fundamentally passive entity that owes its organization to external forces (functions that shape organs) or to an external organizing agent (natural selection). Structuralism (or internalism), is the view that living matter is an intrinsically active entity that is capable of organizing itself from within, with purely internal (...) processes that are based on mathematical principles and physical laws. At the molecular level, the basic mechanism of the Modern Synthesis is molecular copying, the process that leads in the short run to heredity and in the long run to natural selection. The basic mechanism of Systems Biology, instead, is self-assembly, the process by which many supramolecular structures are formed by the spontaneous aggregation of their components. In addition to molecular copying and self-assembly, however, molecular biology has uncovered also a third great mechanism at the heart of life. The existence of the genetic code and of many other organic codes in Nature tells us that molecular coding is a biological reality and we need therefore a framework that accounts for it. This framework is Code biology, the study of the codes of life, a new field of research that brings to light an entirely new dimension of the living world and gives us a completely new understanding of the origin and the evolution of life. (shrink)

The New World of the Organic CodesThe genetic code appeared on Earth at the origin of life, and the codes of culture arrived almost 4 billion years later, at the end of life’s history. Today it is widely assumed that these are the only codes that exist in Nature, and if this were true we would have to conclude that codes are extraordinary exceptions because they appeared only at the beginning and at the end of evolution. In reality, various other (...) organic codes have been discovered in the past few decades.In 1975, the American biochemist Gordon Tomkins published a paper entitled The Metabolic Code. Biological symbolism and the origin of intercellular communication . That was the very first announcement of a new organic code after the discovery of the genetic code, but tragically Tomkins died that very year and his new world of organic symbolism remained unexplored. Some 10 years later, Edward Trifonov started a life-long campaign in favour .. (shrink)