Earth, an ancient, extremely complex, multiple, all-planetary, thermodynamically open, self-controling system of living and non-living matter which accumulates and redistributes immense resources and energy and determines the composition and dynamics of the Earth’s biosphere, lithosphere, cryosphere, atmosphere and hydrosphere and the nonlinear interactions and feedback loops between and within them. These components can be also regarded as self-regulating systems in their own right, and further broken down into more specialized subsystems.
The sources of Earth’s evolving chemical complexity are the energies of solar diurnal disequilibria and the energies of physicochemical gradients at hot hydrothermal vents. The diurnal disequilibria arise naturally when Earth’s rotation converts ‘constant’ solar radiation into cyclic energy gradients that drive chemical reactions at Earth’s oceanic and rocky surfaces; hydrothermal vents release metallic ions and other compounds into the ocean, enriching the ocean’s molecular complexity. How these versatile biomolecules came into being is one of the questions about the origin of life. Amino acids, nucleobases, and various sugars are even found in meteoroids. However, for a peptide to be formed from individual amino acid molecules, very special conditions are required that were previously assumed to be more likely to exist on Earth.
Different chemistries driven by solar radiation and by hydrothermal vents interact, particularly at the three-phase boundary of irradiated tidal seashores, and thus further increase the chances of life’s emergence. Thus, the evolution of primordial chemical compositions and processes was initially driven by Earth’s diurnal cycles that caused repeated colloidal phase separations – the appearances and disappearances of ‘first microspaces’. Today’s microbial cell cycle can be viewed as an ‘evolutionary echo’ from the cyclic chemical disequilibria of the rotating surface of Hadean Earth. The cell cycle had (partially) decoupled from physicochemical diurnal gradients when the stabilization of lipid-protein membranes and information processing allowed cell heredity to take root.
Life, information, and consciousness are entities unique to the biosphere. Each of these three entities has its own properties, physiological behaviors, and physiological functions, but they only appear together as a whole in a living being. That is, the biotic phenomena of life, information, and consciousness cannot exist individually in an organism; they are indivisibly linked, and this is reflected in an organism’s biological behavior as a result of the interaction of its internal environment with its external environment.
Life’s evolution follows a pattern of diversification and subsequent integration of diversity at higher levels of complexity. Throughout evolution this integration has predominantly been achieved through new forms of cooperation and symbiosis.
Life seems little short of miraculous — all those stupid atoms getting together to perform such clever tricks! For centuries, living organisms were regarded as some sort of magic matter. Just ordinary matter doing extraordinary things, all the while obeying the familiar laws of physics. Life is the aspect of existence that processes, acts, reacts, evaluates, and evolves through growth (reproduction and metabolism). The crucial difference between life and non-life (or non-living things) is that life uses energy for physical and conscious development. Life is self-organizing chemistry which reproduces itself and passes on its evolved characteristics, encoded in DNA. In thermodynamics terms, it has the ability to reduce local entropy or disorganization, thus locally contravening the third law of thermodynamics. Life is also a process through which energy and materials are transformed; but so is non-life. Our environment may be conducive to an origin of life and its sustainability. It provides the physicochemical boundaries for life, and considers abiotic, prebiotic and biotic processes. Coevolution is what happens from the moment life comes into being. This concept envisions spatiotemporal interactions between life and environment, and how they modify each other. It is a systemic relationship that takes place through loops and feedback mechanisms and is measured by changes and adaptation. With the Gaia hypothesis, coevolution becomes a symbiotic relationship between life and environment, which evolve together as a single, self-regulating system maintaining the conditions for life on Earth. Gaia is a cybernetic feedback system operated unconsciously by the biota. Habitability, coevolution and Gaia approach life’s origin and its evolution from the astronomical, planetary and ecological perspectives.
From the standpoint of physics, there is one essential difference between living things and inanimate clumps of carbon atoms. The former tend to be much better at capturing energy from their environment and dissipating that energy as heat.
The separation between living and nonliving may not be a fundamental difference of nature between them, but a difference in the amount of energy and complexity of information that is being integrated, organized, stored, transformed and exchanged at any single moment. All matter, including living matter, is subject to the laws of physics.
What, then, is the secret of life’s remarkable properties? Can quantum mechanics play a fundamental role in biology, for example through coherent superpositions and entanglement? Biology and biological processes often deal with electrons and protons that are continuously being transferred between different parts of a cell or a macromolecular system. These transfer processes can only take place when the system exchanges energy with its environment in the form of molecular vibrations and phonons. Such a system is called an ‘open quantum system’, and special physical laws apply to it. Electrons, protons, excitations, chemical bonds, and electronic charges are by definition quantum, and an understanding of their dynamics requires quantum mechanics. Furthermore, these basic entities largely determine the properties of the next level of organization in biological systems – that of biomolecular complexes, whose interaction with one another, and with their environment, often cannot be described accurately without considering the laws of quantum biology.
Good examples of biological processes in which quantum effects are visible are the transport of electrons and protons in photosynthesis, respiration, vision, catalysis, olfaction, and in basically every other biological transport process. Further examples include the transfer of electronic and/or vibrational energy, and magnetic field effects in electron transfer and bird migration.
Although all this adds up to a prima facie case for quantum mechanics playing a role in biology, they all confront a serious and fundamental problem. At first sight, the warm and wet interior of a living cell seems a very unpromising environment for low decoherence. Back-of-the-envelope calculations suggest decoherence times of less than 10–13 s for most biochemical processes at blood temperature. However, there are reasons why real biological systems might be less susceptible to decoherence. One is that biological organisms are highly non-linear, open, driven systems that operate away from thermodynamic equilibrium. The physics of such systems is not well understood and could conceal novel quantum properties that life has discovered before we have. Indeed, sophisticated calculations indicate that simple models generally greatly overestimate decoherence rates. Spin, as a given quantum mechanical property of particles, is the basis of complex matter, such as atoms, molecules, peptides, nucleotides, proteins and cells, and thus of all life. Spin determines the structure and controls the function of all matter. The quantum effects manifest themselves as long-distance effects (like in electron and proton tunneling) with a characteristic temperature dependence, magnetic field effects, the participation of superposition (or delocalized) states, resonance effects, etc.
In recent years, much attention has been given to decoherence, and its avoidance, by physicists working in the burgeoning field of quantum computation and quantum-information science. Effects like coherence, entanglement and superposition can be maintained only if the quantum system avoids decoherence caused by interactions with its environment. In the presence of environmental noise, the delicate phase relationships that characterize quantum effects get scrambled, turning pure quantum states into mixtures and in effect marking a transition from quantum to classical behavior. Only so long as decoherence can be kept at bay will explicitly quantum effects persist. The claims of quantum biology therefore stand or fall on the precise decoherence timescale. If a system decoheres too fast, then it will classicalize before anything of biochemical or biological interest happens.
This theory takes life’s origin to the beginning of the universe. Because it involves interactions at the quantum level, it may also mean a theory of everywhere, in which the separation between living and nonliving is not a fundamental difference of nature between them, but a difference in the amount of energy and complexity of information that is being integrated, organized, stored, transformed and exchanged at any single moment.
But what is life really about, if anything? Is life a meaningless accident arising from the laws of physics operating in a meaningless universe? Life is a creative process towards an increasingly aesthetic experience of the world that is both rich and beautiful.