What is life? Systems of biological development

It is nearly eighty years since the three lectures given by Erwin Schrodinger at Trin- ity College, Dublin were published (Schrodinger 1944). The title that Schrodinger chose for those lectures, and which he maintained in their publication, was: ‘What is Life?’ It’s a simple enough question, and others have since responded, or have posed the same question in the titles of their own works (e.g., Murphy & O’Neill 1995; Margulis & Sagan 1995; Pross 2012; cf. Lazcano 2008). While it has proven possible to list the attributes that many are prepared to accept as being present amongst all living things, it seems that a single, agreed, answer to the question by which life might be defined has remained elusive (Tirard et al. 2010; Kauffman 2019). Nonetheless, all living systems must share a common level of organisation ‘which makes a living system a whole, autonomous unity’ and where ‘reproduction and evolution are not constitutive features of the living organization’ (Varela et al. 1974, 187, my emphasis). The exclusion of reproduction and evolution from the possible definition of life is because a living organism needs to develop to maturity before it is capable of reproducing, and thus before it can contribute to the possible trajectory of an evolutionary sequence. Living things therefore exist and develop before they can reproduce, and in these terms, they can be identified as autopoietic systems (self-producing or self-developing systems) comprising a network of the components that maintain the further production of those same components (by their growth and repair). It is by these processes of self-production that the organism grows to maturity.

The individual human originates as a single fertilised cell (a zygote) in the womb of the mother before that cell then starts to divide to produce the cells that build the organs of the foetus, the child, and then the adult. The biological process of this self-production is common to any complex organism, and it is one in which the components of that organism continue to produce and repair themselves throughout the organism’s lifetime. With the important exception of the foetus’s initial development being dependent upon the mother’s body, this development and ageing proceeds without the work of an external agency (Rosen 1991). By this I mean that the organism has no external designer or labourer, and it is this that distinguishes its making and remaking from the making and repairing of a machine. Biological systems, the simplest example of which is the cellular stage of development, originate by building an enclosing membrane or skin (Hofffneyer 2008, 17-38), and this forms the boundary condition that constrains the operation of the organism’s internal mechanisms (Montevil & Massio 2015). It is across the semi-permeable boundary of this skin that the necessary flows of energy occur which facilitate the internal work of self-production. Starting from the premise that systems of living matter ‘are not adequately described simply as a matter of complex configurations of physical or biochemical processes’ (El-Hani et al. 2009, 5), we must understand that all forms of life are biological systems that can only exist as processes of self-production when entwined within various environmental conditions.

If we hope to understand the origins of life, then it is the origins of these systems of self-producing order that we need to understand and the ways that they metabolise energy (Kauffman 1993), rather than the origins of life originating with the means of biological transmission (reproduction) along with its subsequent evolution. It is from this non-evolutionary perspective that the idea of the gene must also be understood, namely in terms of the way that it functions within the cellular process, rather than from the perspective of its supposed role in the transmission of inherited traits (Schrodinger 1944; Dawkins 1978 [1976J). It has been by emphasising the processes of transmission that the function of the gene’s role in carrying units of information from one generation to the next has been brought to the fore, with the result that the gene has been treated as if the information that it supposedly carried determines the formation of the cell, and thus of the organism as a whole. However, the question that we need to ask is not ‘what does the gene dofor the cell?’, but 4vhat does the cell do with the gene?’ (cf. El-Hani et al. 2009).

The definition of what we might mean by the concept of a gene is certainly complex, even to the point that its physical existence has been questioned (Falk 1986; Fogle 1990). Instead of regarding the gene as a unit of information (Maynard Smith 2000), or indeed as being physically manifest in a particular stretch of DNA, it would be more accurate to treat the gene as the outcome of a process that resulted from the operation of the elements within the cell, and it is this process that gives rise to the cell’s function. The problem then becomes how we should conceive of the processes that are involved in cellular replication and the subsequent growth of the organism. In addressing this problem, I follow the current work on biosemiotics (Hoffineyer 2008; Kull et al. 2009) with its commitment to the Peircean theory of the sign (cf. Hoopes 1991).

The Peircean sign has three elements: (1) the sign vehicle that stands for or indicates (2) some object or value as it is recognised by (3) an interpretant. If the organism is conceived of as an emergent state of becoming that arises from the cellular mechanisms that operate as interpretants, then these interpretive processes employ the chemistry of DNA as a sign vehicle, and they result in the production of proteins. It is these proteins that determine the work that the cell will undertake (its function). This cellular work-cycle is a process sustained by catalysing the energy that can be imported across the cell’s membrane from an environmental substrate. Genes are thus only known to us by the ways that certain sections of the DNA code are expressed, and the idea of the gene satisfies our need to identify the agency that causes the formation of proteins. Consequently, we should accept that genes are the objectification of a process by which the sign vehicle of DNA is interpreted in the building and replication of a cell. DNA is matter, and it is the agency of its interpretation that gets us from that matter to its mattering (cf. Kauffman 2019), a ‘mattering’ which we now characterise by reference to genetics. It follows that the making of life is an interpretive process and the organism’s development is a more complex process than the one implied by the traditional claim that the genes provide a ‘blueprint’ that determines the design of an organism (Moss 2003; Pigliucci 2010).

Given that organisms are built by the accretion of cells, then complex cells (that is eukaryotic cells with a nucleus and with divisions within the surrounding cytoplasm) are, as Lynn Margulis demonstrated, constructed by a process of symbiosis that involves the merger of different simple (prokaryotic) cells. Prokaryotic cells lack a nucleus and are represented today by bacteria and by the biological family of Archaea:

[mjolecular biological, genetic, and high-powered microscopic studies . . .

confirm the once radical nineteenth-century idea that the cells of plants

and of our animal bodies, as well as those of fungi and all other organisms composed of cells with nuclei, originated though mergers of different types of bacteria in a specific sequence. (Margulis 1998, 30)

The implication of Margulis’s work was radical. Whilst ‘the origin of life was concurrent with bacteria’, and given that ‘bacteria do not have species at all’, then speciation is ‘a property only of nucleated organisms’ that originated ‘long after bacteria had evolved nearly all the important metabolic traits displayed by life on earth’ (Margulis & Sagan 2002, 55). The origin of life is not, therefore, the origin of speciation.

An organism is a form of life that is therefore a ‘far from equilibrium’ system, which grows to maturity by the internal agencies of interpretation that are themselves dependent upon the extraction and metabolism of energy from that organism’s environment. The reliable development of complex organisms, as given by their long-lived lineages, occurs ‘because of reliable interactions between the developing organism and its environment’ (Griffiths & Gray 1994, 280). If the reliability of these interactions within an ecology is the process that secures the longterm stability witnessed by the lineage of a form of life, then this counts against the Darwinian assumption that evolutionary change within a species should occur gradually, through the step-by-step modification in the reproduction of individuals, extending over several generations (Darwin 2009 [1859], 278-305). Indeed, the fossil record has failed to reveal these gradual changes (Gould 2002, 840-850; contra Dennett 1996, 282-299), and the fossil record confirms the long-term stability in the phenotypic form of a species (Eldredge 1995, 64-78). This stability is then interspersed by horizons of rapid change with the appearance of new species occurring alongside horizons of extinction. It was in light of empirical evidence such as this that Niles Eldredge and Stephen J. Gould proposed that a model of punctuated equilibria was the better description for the shape of evolutionary change than a model of gradual change (Gould & Eldredge 1977). The important point here is that rapid horizons of ‘phase change’ are to be expected in the history' of complex systems (Kauffman 1995, 116—118), meaning that the empirical observations drawn from the fossil record support an approach which looks to the evolution of complex ecosystems, rather than the evolution of relatively autonomous species, or the natural selection of single, mutating, genetic lineages.

It is this complex process of ecosystemic development that evolves, a process of ‘downward causation’ (Dupre 2010) in which the developing organism is situated within the relations upon which it depends, and it is able to build itself within the changing components of its ecosystem. The relationships of life comprise the flows of materials, energy, and information that are identified from beyond the skin of the organism, and are employed in its development. These ecosystems evolve over time (Oyama 2000), and the description of this form of biocultural evolution could be simply treated as if it were the description of‘all of history’ (Margulis 1998, 24).

If archaeology is concerned to understand the way's that forms of humanness have emerged, rather than being an attempt to explain the reasons for the changing patterns of material residue, then such an archaeology will have to treat those residues as part of the conditions of possibility from which a kind of humanness might have constructed itself. Archaeological materials are the residues of those environments within which forms of life, including forms of humanness, have found it possible to live. Humanness was the agency that interpreted those environments; as Stuart Kauffman puts it, ‘[ajgency introduces meaning into the world! Agency is fundamental to life’ (Kauffman 2019, 91).

 
Source
< Prev   CONTENTS   Source   Next >