It's Time We Had a Definition of Life
In 1943 the eminent physicist Erwin Schrodinger gave a series of lectures in Dublin that were later published in book form under the title What is Life? Its success was considerable as it kick-started the new field of molecular biology, but Schrodinger deliberately avoided an investigation into a definition of life, believing that the time was not ripe.
In more recent times, Fred Adams, professor of physics at Michigan University, in The Origins of Existence--How Life Emerged in the Universe, wrestled manfully with this question, but he eventually concluded that "Achieving a universal definition of life is unquestionably of fundamental importance, but no such definition has yet been forthcoming."
There is a noticeable reluctance among scientists to grapple with this question of life. All are happy to speculate about the conditions that need to exist for life to originate, but none seem inclined to actually define life itself. In The Selfish Gene, for example, Richard Dawkins devoted a page or so to explaining the conditions necessary for its origin, then stated that "At some point a particularly remarkable molecule was formed by accident." He then went on to speculate about the further development of this molecule that he calls a replicator, but failed to explain to his readers what life actually is. A strident critic of Dawkins, Professor Gabriel Dover, in his wonderfully quirky but scientifically illuminating Dear Mr. Darwin, described the conditions necessary for life from a galactic viewpoint, but like Dawkins he omitted a definition. Professor Freeman Dyson, another critic of selfish gene theory, in his excellent Origins of Life, did go so far as to provide the characteristics of life, as did Fred Adams, but these characteristics provide a description, not a definition. These approaches seem to typify the attitude of the scientific community to what appears to be perceived as a difficult subject, but as we press on I hope to show that perception to be misplaced.
Adams specified reproduction and metabolism as the characteristics of life, while Dyson took a similar position but quite pointedly differentiated himself from Dawkins and the simplistic replicator view of life, first stating that "the essence of life from the beginning was homeostasis based on a complicated web of molecular structures ... The tyranny of the replicators was always mitigated by the more ancient cooperative structure of homeostasis that was present in every organism," and with an admirable touch disclosed a personal aspect to the question with the following: "I have been trying to imagine a framework for the origin of life, guided by a personal philosophy that considers the primal characteristics of life to be homeostasis rather than replication, diversity rather than uniformity, the flexibility of the genome rather than the tyranny of the gene, the error tolerance of the whole rather than the precision of the parts."
If we take the three specifics highlighted by Adams and Dyson, homeostasis, reproduction and metabolism, (homeostasis is the ability to maintain a constant chemical balance in a changing environment, metabolism is the chemical processes that occur in cells in particular the consumption of energy, reproduction can be as simple as cell division, but can involve a cell dividing in accordance with a strict code of instructions) we see that all of the characteristics of life are founded on cooperation, either within a single cell between its parts, or between combinations of cells. If we are to examine this from a philosophical viewpoint as Dyson suggests and as I believe we should, then instead of just using physiological processes to define life we must go one step further and look in turn to their essence. But first we should summarize Richard Dawkins' description of life after origin.
After postulating his remarkable replicating molecule, or gene, in the opening chapter of The Selfish Gene, Dawkins returned to its origins in the final chapter to examine its progress thereafter, and asked the questions "Why did genes come together ... Why do they cooperate?" He then spent a full page in not answering the question, instead explaining how they cooperate. He continued "Nowadays this cooperation goes on within cells. It must have started as rudimentary cooperation between self-replicating molecules in the primeval soup (or whatever primeval medium there was)." He's just described the origin of life itself and cannot see its significance.
It's undeniable, from Dawkins' own pen as he continues, that natural selection ensured that:
So far in his description, covering two pages of text, evolution has progressed from the origin of life right through to the modern organism and there's not a selfish gene in sight, despite Dawkins' desperate efforts to give the process a selfish spin. He ignores all this cooperation, seeing it only as a stratagem for individual genes. Now Dawkins is entitled to interpret the activities of genes as he sees fit, but it's clear from his and all other biologists' descriptions of the endless and complex cooperative arrangements that exist in nature, from the level of molecules and compounds through to organisms and societies, that natural selection has ensured that cooperation is the principal contributor to biological fitness. It's also clear that the cooperation engaged in by molecules is evidence that group selection is not just a theoretical possibility that lacks evidence from the natural world, as Dawkins maintains, rather it is the very mechanism that facilitated the initial evolution of life forms. Group selection would appear to be the dominant evolutionary principle.
Can we extract from this a useful definition of life? Can we go deeper than a description of the physiological processes provided by Adams and Dyson? It seems inescapable that life at the molecular level is actually a remarkably simple and basic concept--life is cooperation.
The key here is to return to the very beginning and consider the actual process that saw lifeless molecules assume life. At what point, we must ask, did they assume life? Unquestionably, when the first molecules began demonstrating affinity, then began coalescing, then began cooperating, they began living, for it's at that point that they began performing those functions generally considered to be the characteristics of life. There seems to be no good reason why a definition of life at the molecular level should not hold true as life forms slowly increased in complexity. Indeed, there is nothing about the modern eukaryotic cell, nothing about organisms, nothing about the myriad social arrangements existing in the natural world that undermines this definition. All are wholly dependent on cooperation for survival, and all demonstrate homeostasis, reproduction and metabolism in one form or another. When we think of the truly amazing cooperative processes that make up the immune systems of modern vertebrates for example, it's tempting to suggest that cooperation is more important in complex life forms than in their original ancestral molecules, but those first co-operators must surely remain at the pinnacle of biological significance.
If the biological definition of life is cooperation among molecules, then surely a useful general definition is that life is just simply cooperation. No adjectives, no conditions, life is cooperation. We can test this by asking the reverse question. If life is cooperation, is cooperation therefore life? That might be a question to leave to the philosophers, but at first glance it strikes me that such a case could be mounted as long as conditions are attached. For example, Richard Dawkins used the steam engine to show that an inanimate object can appear to have purpose, but an engine can also demonstrate cooperation between the various parts of the machine to achieve a particular end. We would only refer to it as being alive however in a metaphorical sense, as a machine needs external inputs for initiation and for sourcing of energy. We could perhaps therefore say that independent and spontaneous cooperation is life.
Keep in mind that after the first molecules assumed life, consciousness did not come into the picture for perhaps billions of years, despite our natural inclination to associate and even equate the two. It's this misleading inclination of ours, as conscious beings, to associate life with consciousness that has led to the perception that life is a thorny issue. Our consciousness, after all, is our most precious quality. When we lose our life, we lose our consciousness, so we incorrectly think of life as consciousness. Life however, came first, and consciousness evolved at a later point. Life is far more basic and easier to explain than consciousness, and the very simplicity of the definition of life given here has consequences that might have contributed to the reluctance of some to delve too deeply into its meaning.
For example, life as cooperation consigns much of the trappings of selfish gene theory to the dust-bin of history, along with a multitude of social attitudes, beliefs and prejudices such as the foundations of competitive market philosophy. It provides molecular-level evidence for Charles Darwin's contention, ignored by mainstream science, that mankind's social instincts are primary and individual instincts secondary, and for Peter Kropotkin's argument that mutual aid played a more significant role in the evolution of life forms than competition. It corrects and redirects the unconscious bias that has plagued "pure" research for millennia, the bias in favor of cerebral development as the major influence on human evolution rather than the demonstrably more important contribution of labor, labor being in the main a cooperative venture. (This last matter was covered by Stephen Jay Gould in his essay "Posture Maketh the Man" in which he highlighted the overwhelming detrimental influence of class attitudes on the direction of scientific research.) In short, the definition of life as cooperation has far-reaching implications, not only because it turns conventional theory on its head, but because it finally gives us a starting point, a firm footing on which to base our future considerations regarding the social good.
 Fred Adams, Origins of Existence: How Life Emerged in the Universe (New York, The Free Press, 2002), p. 167.
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