What is Life?:How chemistry becomes biology
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The network perspective on life might assist in addressing some of the questions concerning life that have been frequently raised over the years. Based on the theory of life proposed here, replication is the essence of life. That might seem to imply that a mule or lone rabbit would not be considered alive, as neither can reproduce. But, of course, mules (and lone rabbits) are alive. It is true that they cannot reproduce but they are still part of the replicative network—they are just dead-ends. A road that stops in a dead-end is still a road and part of the road network. Mules are replicative entities, not because they can reproduce—they can’t—but because of the replicative process by which they came into being. What about viruses—are they alive? One can conduct lengthy debates on the matter and ultimately the answer would depend on one’s precise definition of a living thing. Clearly viruses are lacking key life characteristics, such as possessing an independent metabolism. Having said that, however, there is no doubting that viruses are also an integral part of the life network. For viruses the question is more philosophic and linguistic than scientific.
The merging of chemistry and biology
The goal of this book has been to demonstrate that answers to several of the most central of life questions, including the classic one posed by Schrödinger, are finally becoming accessible. The extraordinary powers of science and the inductive method in particular, have revolutionized our lives and our understanding of the world to an extent we could not have foreseen, even a century ago. Thanks to the remarkable scientific progress these past 150 years, from Darwin’s awesome revolution in biological thinking, through to the exciting new developments in systems chemistry, biology and chemistry are finally merging, finally becoming one. The Darwinian revolution may now be nearing its ultimate goal, the one that Charles Darwin already foresaw 130 years ago—the integration of the biological sciences within the physical sciences. That merging of the two sciences means that within the limits that science itself imposes on us, we can begin to understand what is life, why it emerged, how we, a twiglet on the tree of life, together with all other living things on our planet, relate to the material world and the universe as a whole, and why, despite the unforgiving harshness of the Darwinian view, we are committed to one another, why in some deeper sense, we are one. Can that fundamental life connection serve as a ray of hope for the future of humankind, the entity that Stephen Hawking called ‘a chemical scum on a moderate-sized planet’? Only time will tell.
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INDEX
abiogenesis 126, 182
Allen, Woody 50, 167
alien life 178
Altman, Sydney 105
archaea 3, 89
Aristotle 32, 33
autocatalysis 62–5, 68, 151
bacteria 90
bacterial diversity 23, 24
Bohr, Niels 36
Brenner, Sydney 53
catalysis 61, 62, 151, 152
Cech, Thomas 105
chemical reactions 58
chemotaxis 15–16 chirality 27, 28
Chyba, Christopher 41
Ciechanover, Aaron 22
Cleland, Carol 41
competitive exclusion principle 128
complexity 4
consciousness 177
Conway, John 119
Cornish-Bowden, Athel 57
Crick, Francis 54, 55, 83
cyanobacteria 74, 75
Darwinian theory 8, 34, 35, 112, 113, 117, 183, 184
Dawkins, Richard 4, 76
death 170
De Duve, Christian 108
definition of life 40, 164
Delbrück, Max 88
dissipative structure 118
diversity 171
DNA 38, 69, 151
dynamic kinetic stability (DKS) 73, 75, 78, 141, 144–6, 149, 150, 164, 166–9, 172
dynamic stability 71
Dyson, Freeman 103
earth’s age 87
Eigen, Manfred 142, 143
Einstein, Albert 47
entropy 62
eukarya 90
Feynman, Richard 47, 101
finches, Darwin’s 129
fitness 140, 141, 147, 148
fitness landscape 142
game of life 119
Ganti, Tibor 115
general theory of evolution 153
Grand, Steve 76
Haeckel, Ernst 35
Haldane, J.B.S. 83
Hawking, Stephen vii, 191
Hershko, Avram 22
hierarchical reduction 53, 137
holism 50–7 homeostasis 6
homochirality 28, 29, 174, 175
horizontal gene transfer 91
human genome project 113
induction 43
information 150–3
Jobs, Steve 170
Joyce, Gerald 128, 129, 132–4, 159, 166
Kauffman, Stuart 102, 114
kinetic selection 138, 139
kingdoms of life 90
Last Universal Common Ancestor
(LUCA) 88, 91, 173
Lifson, Shneior 107
Lotka, Alfred 138, 164