The Biological Universe (Dick 1996) analysed the history of the extraterrestrial life debate, documenting how scientists have assessed the chances of life beyond Earth during the 20th century. Here I propose another option – that we may in fact live in a postbiological universe, one that has evolved beyond flesh and blood intelligence to artificial intelligence that is a product of cultural rather than biological evolution. MacGowan & Ordway (1966), Davies (1995) and Shostak (1998), among others, have broached the subject, but the argument has not been given the attention it is due, nor has it been carried to its logical conclusion. This paper argues for the necessity of long-term thinking when contemplating the problem of intelligence in the universe. It provides arguments for a postbiological universe, based on the likely age and lifetimes of technological civilizations and the overriding importance of cultural evolution as an element of cosmic evolution. And it describes the general nature of a postbiological universe and its implications for the search for extraterrestrial intelligence.

While early eukaryotic life must have been unicellular, multicellular lifeforms evolved multiple times from protistan ancestors in diverse eukaryotic lineages. The origins of multicellularity are of special interest because they require evolutionary transitions towards increased levels of complexity. We have generated new sequence data from the nuclear large subunit ribosomal DNA gene (LSU rDNA) and the SSU rDNA gene of several unicellular opisthokont protists – a nucleariid amoeba (Nuclearia simplex) and four choanoflagellates (Codosiga gracilis, Choanoeca perplexa, Proterospongia choanojuncta and Stephanoeca diplocostata) to provide the basis for re-examining relationships among several unicellular lineages and their multicellular relatives (animals and fungi). Our data indicate that: (1) choanoflagellates are a monophyletic rather than a paraphyletic assemblage that independently gave rise to animals and fungi as suggested by some authors and (2) the nucleariid filose amoebae are the likely sister group to Fungi. We also review published information regarding the origin of multicellularity in the opisthokonts.

The oft-repeated claim that life is ‘written into’ the laws of nature is examined and criticised. Arguments are given in favour of life spreading between near-neighbour planets in rocky impact ejecta (transpermia), but against panspermia, leading to the conclusion that if life is indeed found to be widespread in the universe, some form of life principle or biological determinism must be at work in the process of biogenesis. Criteria for what would constitute a credible life principle are elucidated. I argue that the key property of life is its information content, and speculate that the emergence of the requisite information-processing machinery might require quantum information theory for a satisfactory explanation. Some clues about how decoherence might be evaded are discussed. The implications of some of these ideas for ‘fine-tuning’ are discussed.

To recognize alien life, we would have to be clear about the defining criteria of ‘life’. Metabolism – in other words, biochemical fine-tuning – is one of these criteria. Three senses of metabolism are distinguished. The weakest allows strong artificial life (A-life): virtual creatures having physical existence in computer electronics, but not bodies, are classed as ‘alive’. The second excludes strong A-life but allows that some non-biochemical A-life robots could be classed as alive. The third, which stresses the body's self-production by energy budgeting and self-equilibrating energy exchanges of some (necessary) complexity, excludes both strong A-life and living non-biochemical robots.

It has been concluded from measurements, recently made by Mars Odyssey experiments, that there is water in the upper few metres of the Martian surface at mid- and equatorial latitudes with regionally high contents of up to about 9 wt%. This Martian subsurface water is shown to be in the form of adsorption (or sorption) water. The adsorptive bond of water molecules is about twice as strong on mineral surfaces compared with on water ice. Therefore, evaporation of adsorption water in porous soil happens on time scales, which exceed those of sublimation of water ice by orders of magnitude. Consequently, sorption water can have survived in the near-surface layers of the Martian soil at mid- and equatorial latitudes over geological time scales, where ice must have been lost by sublimation. Sorption water is unfrozen, i.e. liquid-like, down to temperatures of −40°C and below. It must, at least regionally and temporarily, be an important and not a trace constituent of the upper-surface Martian soil. The presence of liquid-like sorption water on Mars is also discussed in view of exobiological implications.

Random Boolean networks (RBM) were introduced about 35 years ago as first crude models of genetic regulatory networks. RBNs are comprised of N on–off genes, connected by a randomly assigned regulatory wiring diagram where each gene has K inputs, and each gene is controlled by a randomly assigned Boolean function. This procedure samples at random from the ensemble of all possible NK Boolean networks. The central ideas are to study the typical, or generic properties of this ensemble, and see 1) whether characteristic differences appear as K and biases in Boolean functions are introducted, and 2) whether a subclass of this ensemble has properties matching real cells.

Such networks behave in an ordered or a chaotic regime, with a phase transition, ‘the edge of chaos’ between the two regimes. Networks with continuous variables exhibit the same two regimes. Substantial evidence suggests that real cells are in the ordered regime. A key concept is that of an attractor. This is a reentrant trajectory of states of the network, called a state cycle. The central biological interpretation is that cell types are attractors. A number of properties differentiate the ordered and chaotic regimes. These include the size and number of attractors, the existence in the ordered regime of a percolating ‘sea’ of genes frozen in the on or off state, with a remainder of isolated twinkling islands of genes, a power law distribution of avalanches of gene activity changes following perturbation to a single gene in the ordered regime versus a similar power law distribution plus a spike of enormous avalanches of gene changes in the chaotic regime, and the existence of branching pathway of ‘differentiation’ between attractors induced by perturbations in the ordered regime.

Noise is serious issue, since noise disrupts attractors. But numerical evidence suggests that attractors can be made very stable to noise, and meanwhile, metaplasias may be a biological manifestation of noise. As we learn more about the wiring diagram and constraints on rules controlling real genes, we can build refined ensembles reflecting these properties, study the generic properties of the refined ensembles, and hope to gain insight into the dynamics of real cells.

Nitrogen is an essential element for life. Specifically, fixed nitrogen (i.e. NH3, NH4+, NOx or N that is chemically bound to either inorganic or organic molecules and can be released by hydrolysis to form NH3 or NH4+) is useful to living organisms. Nitrogen on present-day Mars has been analysed only in the atmosphere. The inventory is a small fraction of the amount of nitrogen presumed to have been received by the planet during its accretion. Where is the missing nitrogen? Answering this question is crucial for understanding the probability of the origin and evolution of life on Mars, and for its future astrobiological exploration. The two main processes that could have removed nitrogen from the atmosphere include: (1) non-thermal escape of N atoms to space and (2) burial within the regolith as nitrates and ammonium salts. Nitrate would probably be stable in the highly oxidized surface soil of Mars and could have served as an NO3− sink. Such accumulations are observed in certain desert environments on Earth. Some NH4+ nitrogen may also be fixed and stabilized in the soil by inclusion as a structural cation in the crystal lattices of certain phyllosilicates replacing K+. Analysis of the Martian soil for traces of NO3− and NH4+ during future missions will provide important information regarding the nitrogen abundance on Mars. We hypothesize that Mars soil, as typical of extremely dry desert soils on Earth, is likely to contain at least some of the missing nitrogen as nitrate salts and some fixed ammonium bound to aluminosilicate minerals.

Silicic acid increased numbers of both aerobic and facultatively anaerobic bacteria in ultrapure water incubated under strict oligotrophic conditions; soil extracts acted as the bacterial inoculum. The results are discussed in relation to the possibility that silicic acid, produced by the hydrolysis of silicates on the early Earth, could have stimulated the growth of the first bacterium, thereby allowing it to become established in the then prevailing conditions (presumed to be oligotrophic).

I shall present three arguments for the proposition that intelligent life is very rare in the universe. First, I shall summarize the consensus opinion of the founders of the modern synthesis (Simpson, Dobzhanski and Mayr) that the evolution of intelligent life is exceedingly improbable. Secondly, I shall develop the Fermi paradox: if they existed, they would be here. Thirdly, I shall show that if intelligent life were too common, it would use up all available resources and die out. But I shall show that the quantum mechanical principle of unitarity (actually a form of teleology!) requires intelligent life to survive to the end of time. Finally, I shall argue that, if the universe is indeed accelerating, then survival to the end of time requires that intelligent life, though rare, to have evolved several times in the visible universe. I shall argue that the acceleration is a consequence of the excess of matter over antimatter in the universe. I shall suggest experiments to test these claims.

A recurrent argument against the reality of biological evolution is the claim that there is insufficient time for the emergence of biological complexity. Such a view is a staple of creation ‘scientists’, but even cosmologists and biochemists have been overheard murmuring similar sentiments. Certainly the stock response, that the scientific evidence for evolution is overwhelming, must be made. However, it is also the case that whilst the efficacity of natural selection is not in dispute, it is context-free and fails to explain the specificities of life. This observation is usually greeted with a Gallic shrug: ‘Yes, the biosphere is very rich, but so what?’ Indeed, the standard scientific response is that evolution is dogged by contingent happenstance, with the implication that a given complexity, say intelligence, is an evolutionary fluke. This, however, is inconsistent with the ubiquity of evolutionary convergence. Here I outline the argument for such convergence providing a ‘road-map’ of possibilities that arguably has universal applications and as importantly points to a much deeper structure to life.