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 necessary 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 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 and 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 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 the selfish gene 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 code of instructions) we see that all of the characteristics of life are founded on cooperation, either within a 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 it would be useful to examine 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 questions, instead explaining how they cooperate. He continued “Nowadays much of this cooperation goes on within cells. It must have started as rudimentary cooperation between self-replicating molecules in the primeval soup.” It’s undeniable, from Dawkins’ own pen as he continued, that:
· Those replicators that cooperated had greater biological fitness: “it (a gene) flourishes only in the presence of the right set of other genes.”
· Only those that acted collectively underwent further development: “But cooperation between genes did not stay limited to cellular biochemistry. Cells came together to form many-celled bodies.”
· Those replicators that created walls to protect the society of genes had greater biological fitness: “Cell walls perhaps arose as a device to keep useful chemicals together…”
· Those that acted as though the society was greater than the individual, and could undertake specialised functions that contributed to the social good had greater biological fitness: “The cells in the club can specialise, each therefore becoming more efficient at its particular task. Specialist cells can serve other cells in the club and they also benefit from the efficiency of other specialists.”
It’s clear from the work of Dawkins 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 those first replicating 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.
When we think of the truly amazing cooperative processes that make up the immune systems of modern vertebrates for example, it’s tempting to think 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.
Can we extract from this a useful definition of life? Can we go deeper than a description of the physiological processes outlined 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 process that saw lifeless molecules assume life. At what point we must ask, did they assume life? Unquestionably, when the first molecules began coalescing, then began cooperating, they began living, for it’s at that point that they began performing those functions that we generally consider 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 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, metabolism and reproduction in one form or another. (The forms may differ, but all have mechanisms for maintaining stability, for intake and consumption of energy, and for reproduction.)
If the definition of biological life is cooperation among molecules, then possibly a useful general definition is that life is just simply cooperation. We can test this by asking the reverse question. If life is cooperation, is cooperation therefore life? It strikes me that such a case could be mounted as long as conditions are attached. For instance, an engine demonstrates cooperation between its various parts to achieve a particular end, but we would only refer to it as being alive in a metaphorical sense, as an engine needs external inputs for initiation and for sourcing of energy. The limitations of the engine example however, lead us in the right direction for a general definition. We can conclude as a general rule that independent spontaneous cooperation is life.
There’s one important fact that stands out like a beacon from this discussion. Cooperation preceded evolution. All else is commentary. (Apologies to Wilson and Wilson!)
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 as conscious beings to confuse the two and equate consciousness with life. Life is far more basic and easier to explain than consciousness, and the very simplicity of the definition given here has consequences that might have contributed to the reluctance of some to delve too deeply into its meaning. But that is another story.