Description / Table of Contents:
INTRODUCTION: WHAT IS LIFE?
I’m not going to answer this question. In fact, I doubt if it will ever be possible to give a full answer. (Haldane, 1949: 58)
What Is Life?
J. B. S. Haldane (1949) and Erwin Schrödinger (1944), two of the twentieth century’s most influential scientists, posed the direct question, ‘what is life?’ and declared that it was a question unlikely to find an answer. Life, they suggested, might exceed the ability of science to represent it and even though the sciences of biology, physics and chemistry might usefully describe life’s structures, systems and processes, those sciences should not seek to reduce it to the sum of its parts. While Schrödinger drew attention to the physical structure of living matter, including especially the cell, Haldane asserted that ‘what is common to life is the chemical events’ (1949: 59) and so therefore life might be defined, though not reduced, to ‘a pattern of chemical processes’ (62) involving the use of oxygen, enzymes and so on.
Following Schrödinger and Haldane, Chris McKay’s article, published in 2004 and included in this collection, asks again ‘What is Life – and How Do We Search For It in Other Worlds?’. For him, the still open and unresolved question of life is intrinsically linked to the problem of how to find it (here, or elsewhere) since, he queries, how can we search for something that we cannot adequately define? It should be noted that this dilemma did not deter the founders of Artificial Life, a project that succeeded Artificial Intelligence and that sought to both simulate ‘life-as-we-know-it’ and synthesise ‘life-as-it-could-be’ by reducing life to the informational and therefore computational criteria of self-organisation, self-replication, evolution, autonomy and emergence (Langton, 1996: 40; Kember, 2003). McKay concedes that certain characteristics of life, such as metabolism and motion, can occur without biology, but rather than pursuing contestable (re)definitions of life that could not, for him, constitute the basis for a search, he prefers to ask a more pragmatic question: ‘what does life need?’. The elements that support life – energy, carbon, liquid water, nitrogen, sulphur and phosphorus – are not contested and, barring only liquid water, they are abundant in the Solar System. It seems logical then, McKay argues, to search for life indirectly, by looking at where the water is. The case for liquid water on Mars has, as we will see, a long and argumentative history. In as far as the current case is, as McKay maintains, ‘tight’, then there is justification for his upbeat assessment that, with the correct instruments, it should be possible to find life-as-we-know-it – and even life-as-it-could-be. He writes: ‘while it could be similar at the top (ecological) and bottom (chemical) levels, life on Mars could be quite alien in the middle, in the realm of biochemistry’ (2004: 1261).