Intelligence as a Planetary Scale Process
* Frank A, Grinspoon D, Walker S (2022). Intelligence as a planetary scale process. International Journal of Astrobiology 21,47–61. doi
This article proposes a four-stage evolution, three of which have already evolved:
- a planet with a immature biosphere: no planetary intelligence
- a planet with a mature biosphere: emergence of planetary intelligence through cooperation amongst species
- a planet with a immature technosphere: humans produce technology that endangers the biosphere
- a planet where humanity is able to manage the effects of its technosphere for long-term sustainability of the biosphere
Abstract
"Conventionally, intelligence is seen as a property of individuals. However, it is also known to be a property of collectives. Here, we broaden the idea of intelligence as a collective property and extend it to the planetary scale. We consider the ways in which the appearance of technological intelligence may represent a kind of planetary scale transition, and thus might be seen not as something which happens on a planet but to a planet, much as some models propose the origin of life itself was a planetary phenomenon. Our approach follows the recognition among researchers that the correct scale to understand key aspects of life and its evolution is planetary, as opposed to the more traditional focus on individual species.
We explore ways in which the concept may prove useful for three distinct domains:
- Earth Systems and Exoplanet studies;
- Anthropocene and Sustainability studies;
- and the study of Technosignatures and the Search for Extraterrestrial Intelligence (SETI).
We argue that explorations of planetary intelligence, defined as the acquisition and application of collective knowledge operating at a planetary scale and integrated into the function of coupled planetary systems, can prove a useful framework for understanding possible paths of the long-term evolution of inhabited planets including future trajectories for life on Earth and predicting features of intelligentially steered planetary evolution on other worlds."
Contents
Adam Frank et al. :
"First, we will examine whether it is possible to consider intelligence, or some form of cognition, operating on a planetary scale even on those worlds without a planetary-scale technological species (Fig. 1(a) and (b)). This would require some form of collective cognition to have been a functional part of the biosphere for considerably longer than the relatively short tenure of human intelligence on Earth. If true, then the inherently global nature of the complex, networked feedbacks which occur in the biosphere may itself imply the operation of an ancestral planetary intelligence.
Second, we wish to consider whether the changes humans have been introducing to the planet through our industrial activitiesthe changes marking the ‘Anthropocene’ geological epoch (Crutzen, 2002; Steffen et al., 2015)– may be understood as a transition in both the kind and level of global cognitive activity. Here, we are interested in the emergence of networks of processes that originate with human agency but become active and autonomously operate on levels beyond individuals. Thus, we will consider the idea of an emerging technosphere and its place in the Anthropocene (Fig. 1(c), Haff, 2014a, 2014b).
A focus on the Anthropocene allows us to assess the sustainability requirements for a long-lived industrial planetary civilization through the lens of planetary intelligence. Many current threats to sustainability are characterized by inadvertent planetary-scale changes in the environment. These are caused by our aggregate activities being unguided by an awareness of their global scale consequences (Grinspoon, 2016). It is not hard to argue that the long-term survival of our, or any global scale ‘project of civilization’ will require a fundamentally different mode of planetary-scale behaviour in which knowledge of planetary-scale impacts feeds back on, and modulates, behaviour in an intentional loop (e.g. perhaps mediated by artificial intelligence as our systems become increasingly integrated). This means we will need to consider the question of timescales within such feedback loops and also the scale at which decisions are made. We note that decisions favouring the sustainability of collectives may not be the same as the preferences favoured by individuals. A clear but simple example in social choice theory is Arrow’s Impossibility Theorem. Arrow’s theorem demonstrates how, based on a simple set of reasonable assumptions, there is no possible way to rank the preferences of choices made by individuals into a ranked set of preferences for a collective (Arrow, 1950). That is, a collectives’ rankings among a set of choices will not reflect that of its individual members in any procedural way. The idea of planetary-scale collective cognition brings with it the question: would planetary behaviour dominated by stabilizing feedback between awareness and consequences represent a new type, or new level of planetary intelligence? If so, then our concept also takes on an aspirational quality. A deeper understanding of the transition to this mode could be useful for the project of building a sustainable global civilization (United Nations, 2015). Finally, we wish to generalize these questions beyond the singular example of terrestrial history by asking whether planetary intelligence is likely to be a property of some (or perhaps most) inhabited worlds elsewhere in the universe, or at least the longlived ones we are most likely to remotely detect (Fig. 1(d)). This implies that past, current and potential future transitions in Earth’s history may have counterparts on other planets. Work on the ‘Astrobiology of the Anthropocene’ (Haqq-Misra and Baum, 2009; Frank and Sullivan, 2014; Frank et al., 2017, 2018; Mullan and Haqq-Misra, 2019) has already indicated that technological civilizations engaging in large-scale energy harvesting could trigger strong climate-changing feedbacks. The transition to long-term sustainable forms of such civilizations (if such a thing is possible) may have general, generic features which themselves involve transitions in planetary intelligence (Grinspoon, 2016). This line of inquiry can help us to both reflect upon terrestrial evolution from a less parochial perspective and formulate potential paths and states for planetary scale cognition on other planets. Such an effort may also be useful in deriving new observable diagnostics for ‘exo-civilizations’ by articulating characteristics of technological civilizations which can be detected from a distance (aka ‘technosignatures’). Thus, a characterization of planetary intelligence and its role in planetary evolution may be particularly useful for technosignature studies which currently represent a new and highly active direction in astrobiology and SETI (Genio and Wright, 2018; Wright et al., 2020)."
Typology
Frank A, Grinspoon D, Walker S:
Four possible domains of planetary intelligence
(a) "On a planet with an immature biosphere (such as the Earth during the Archean Eon) there are insufficient feedback loops between life and geophysical coupled systems to exert strong co-evolution.
(b) On a planet with a mature biosphere (such as Earth after the Proterozoic) the biosphere exerts strong forcing on the geophysical state establishing full co-evolution of the entire system. This feedback may provide some degree of long-term stabilizing (i.e. Gaian) modulations for the full system.
(c) On a planet with an immature Technosphere (represented by the current Anthropocene Earth) feedbacks from technological activity produce strong enough forcing on the coupled planetary system to drive it into new dynamical states. These forcings however are unconstrained by intention relative to the health of the civilization producing the technology.
(d) On a planet with a mature Technosphere, feedback loops between technological activity and biogeochemical and biogeophysical states have been intentionally modified to ensure maximum stability and productivity of the full system. Alongside each planetary image, we show a schematic atmospheric spectrum.
An immature biosphere would show an atmosphere mostly in equilibrium dominated perhaps by CO2. In a mature biosphere life would have changed atmospheric chemistry leading to a highly non-equilibrium state such as perhaps high concentrations of O2. In an immature Technosphere new ‘pollutant’ species appear, such as CFCs, while industrial activities such as combustion may alter the abundance of other preexisting gases like CO2 and methane. In a mature Technosphere all atmospheric constituents may have their concentrations modified to produce long-term stable and productive states for the full (civilization + biosphere) system. This is represented via a range of possible peaks for different constituents."
Schematic representation of the evolution of coupled planetary systems in terms of degrees of planetary intelligence
"Schematic representation of the evolution of coupled planetary systems in terms of degrees of planetary intelligence.
We propose five possible properties required for a world to show cognitive activity operating across planetary scales (i.e. planetary intelligence).
These are:
(1) emergence,
(2) dynamics of networks,
(3) networks of semantic information,
(4) appearance of complex adaptive systems,
(5) autopoiesis.
Different degrees of these properties appear as a world evolves from abiotic (geosphere) to biotic (biosphere) to technologic (technosphere). While the extent of each property shown in the histogram to the right is meant to be schematic, they represent a proposed evolutionary trajectory whereby a planet develops greater or lesser degrees of self-organizing and self-sustaining complexity. Thus, in the path from an abiotic world to one with a mature biosphere, the evolution of life pushes the planet from one which could not be described as a global complex adaptive system and did not exhibit autopoiesis to one in which those properties are both present and robust. Likewise, an immature technosphere actually shows lower degrees of planetary intelligence than a mature biosphere because key properties such as autopoietic sustainability have been reduced."
Classification for planets based on the degree of thermodynamic complexity
Adam Frank et al. :
"In Frank et al. (Reference Frank, Carroll-Nellenback, Alberti and Kleidon2018), a classification for planets was proposed based on the degree of thermodynamic complexity in the coupled systems (Frank et al., Reference Frank, Carroll-Nellenback, Alberti and Kleidon2017).
A Class I world, like Mercury, has no atmosphere and so can only reradiate low entropy incoming stellar flux as a higher entropy, lower temperature blackbody.
With the addition of an atmosphere, Class II worlds can tap free-energy gradients generated by incoming solar radiation (i.e. temperature differences between the surface and atmosphere) to do work and generate dissipative structures/processes like convective circulation and evaporation/condensation cycles.
Class III worlds include ‘thin’ biospheres which can locally modify conditions tapping free energy (such as chemical gradients) generated by abiotic processes. On Class IV worlds, the biosphere is ‘thick’ (or ‘mature’) meaning it generates a complex network of processes that exert strong global forcings on the other planetary systems (Fig. 2).
Higher levels of dissipation, and therefore disequilibrium, are expected in going from Class I to Class IV worlds. Such a ‘run’ of disequilibrium is, in fact, seen in the solar system in going from Venus, Mars and Titan to Earth (Krissansen-Totton et al., Reference Krissansen-Totton, Bergsman and Catling2016; Frank et al., Reference Frank, Carroll-Nellenback, Alberti and Kleidon2017). Models also show that in moving from the Archean (a thin immature biosphere) to the current thick, mature biosphere, the Earth System has also seen a temporal rise in disequilibrium (Krissansen-Totton et al., Reference Krissansen-Totton, Olson and Catling2018).
The final classification in this scheme was a Class V planet which included a civilization (i.e. a technosphere, Figs. 1 and 2), that had come into a long-term, stable relationship with the other coupled systems. By extending the properties/features of the other classes to a world with a technosphere, Frank et al. (Reference Frank, Carroll-Nellenback, Alberti and Kleidon2018) sought to articulate the characteristics of energy-intensive civilizations that had reached biogeochemical and biogeophysical steady-states with their host worlds (i.e. mature technospheres). The deployment of planetary scale cooperative dynamics with the biosphere was imagined to be one aspect of achieving these states. One example considered was the large-scale ‘greening’ of deserts to make the biosphere more diverse and productive for its own functioning (Becker et al., Reference Becker, Wulfmeyer, Berger, Gebel and Münch2013; Bowring et al., Reference Bowring, Miller, Ganzeveld and Kleidon2013).
From the perspective of the goals of this paper, the generation of robust and stable steady-states between technospheres, biospheres and the other coupled systems would involve the clearest example of planetary intelligence. Here the collective agency of the individual components of the technosphere and biosphere are marshalled for explicitly planetary scale goals. Like the early stage Anthropocene, a Class V world includes a technosphere giving it the first set of characteristics in our definition of planetary intelligence: emergence; networks of semantic information flow; the operation of the technosphere as a CAS including the functioning of signal-sensitive boundaries. Unlike the early stage Anthropocene (which we have argued is an immature Technosphere) the mature technosphere on a Class V planet would have achieved operational closure by deliberately adapting its own activities to function within the limits (temporal and spatial) of the other planetary systems. Thus, a mature technosphere would not function independently from the other systems. Instead, it would have adapted to function within the boundaries of a newly enlarged whole that includes its own activities. In short, a class V planet would exhibit planetary scale intelligence (cognitive activity) and, as such, would be autopoietic.
Grinspoon (Reference Grinspoon2016) has argued that Class V worlds could represent the beginning of planet's entering not just a new geological epoch, as in the Anthropocene, but a new eon, which could continue for hundreds of millions of years or more. Just as the other recognized eon boundaries in Earth history can be seen to represent transitions in the functional relationships between the biosphere and the rest of the Earth system, this ‘sapezioc’ eon would involve the application of not just cognition via semantic information flows operating on planetary scales but of wisdom in the sense of ‘the ability to act with judgment born of experience’. Thus, planets in a sapezoic phase would be those in which wise self-management (i.e. the civilization's construction of the technosphere) and wise planetary management are one and the same. The mechanisms for self-management must themselves be collective and global in scale. (Arguably, a benevolent dictator would not constitute a planetary intelligence because the control is local.)
Once again, we should consider the question of feedback timescales. In Fig. 5, we present a schematic diagram of timescales for feedback or ‘interventions’ at work in the different kinds of planets we have been discussing in this paper. These can be described either in terms of the five classes discussed in Frank et al. (Reference Frank, Carroll-Nellenback, Alberti and Kleidon2017) or as is done in this paper via the immature/mature biosphere/technosphere distinctions. For so-called ‘mature biospheres’, the feedbacks represent networks operating via the coupled planetary systems across a range of timescales from decades (DMS ocean temperature regulation) to CH4 climate regulation across millions of years. Note these may or may not be explicitly Gaian in terms of producing a homeostatic regulation. For ‘immature technospheres’, the feedbacks or interventions will be inadvertent. They are the unintentional consequences of the civilization's activity occurring in decades to century timescales. For ‘mature technospheres’, however, the interventions will be intentional. They will be purposely Gaian and designed to maintain the sustainability of both the biosphere and the technosphere as a coupled system. At the short end, ozone replenishment and climate mitigation would occur on decades to century timescales. Terraforming of uninhabited worlds (if possible) is estimated to require up to 1000-year timescales. Planetary defence from asteroids would require the development of systems that would operate over timescales for ‘city buster’ impacts (>1000 years). At the longest timescales and highest technological capacity, intentional changes in stellar evolution (if possible) to prolong habitability would occur over millions of years."
History
i.e. evolution of the key concepts related to planetary intelligence:
"Consideration of planetary scale cognitive activity goes back to the formative development of biogeochemistry, Earth Systems' Science and Astrobiology. Indeed, the modern concept of the biosphere can be traced to the work of Vernadsky, the founder of both geochemistry and biogeochemistry (Vernadsky, Reference Vernadsky1998). It was Vernadsky who saw that the aggregate activity of life on Earth must be considered part of a system – the biosphere – which strongly couples to the other planetary systems: atmosphere, hydrosphere, cryosphere and lithosphere. In his view, this coupling was driven by the thermodynamics of free-energy gradients (Kleidon, Reference Kleidon2010).
As Vernadsky wrote,
- ‘Activated by radiation, the matter of the biosphere collects and redistributes solar energy and converts it ultimately into free energy capable of doing work on Earth. A new character is imparted to the planet by this powerful cosmic force. The radiations that pour upon the Earth cause the biosphere to take on properties unknown to lifeless planetary surfaces, and thus transform the face of the Earth.’
For Vernadsky, the biosphere was an emergent phenomenon that appeared with, and evolved in tandem with the diversity of individual species. Indeed, the evolution of such species could only be fully accounted for in the context of the wider biosphere. But this emergence, he argued, always involved some degree of cognitive or ‘cultural’ activity.
After developing the concept of the biosphere, Vernadsky went on to explore the concept of the Noosphere (‘noos’ being Greek for Mind). Unlike Teilhard de Chardin's explicitly theological version of the idea, for Vernadsky the Noosphere was an emergent shell of influence based on the totality of what he called ‘cultural biogeochemical energy’. In using the term ‘culture’, Vernadsky meant collective cognitive activity. He held that such activity had always been present in the biosphere from microbes to mammals. But, he argued, the collective cognitive activity in these species, and hence in the biosphere, was insignificant in both measure and impact until the development of Homo Sapiens' scientific and industrial activity.
While Vernadsky thought that ‘cultural biogeochemical energy’ was a minor player in the biosphere until recently, Lynn Margulis had her own conception of the idea and believed it played a larger role in planetary evolution via the Gaia Theory she famously developed along with James Lovelock. The Gaia Hypothesis, as first developed by Lovelock held that Earth's life was able to maintain global conditions, such as average temperature, within a range that kept the planet habitable . Lovelock argued this would occur through negative feedbacks between life and planetary geochemistry. These feedbacks would act to keep perturbations in global conditions in check. What Margulis brought to the collaboration was a focus on the remarkable capacities of microbes to serve as drivers for Gaian feedbacks.
What matters for our concerns is that through her research on evolutionary cooperation (as opposed to competition), Margulis saw the microbial domains as rich with a kind of ‘pre-intelligence’. As she wrote ‘the view of evolution as chronic bloody competition … dissolves before a new view of continual cooperation, strong interaction, and mutual dependence among life forms. Life did not take over the globe by combat, but by networking’ (Margulis and Sagan, Reference Margulis and Sagan1986, p. 122).
Gaia was not, however, to be seen as an organism. As Margulis wrote ‘[Gaia] is an emergent property of interaction among organisms, the spherical planet on which they reside, and an energy source, the Sun’ . This concept of the emergence of a new planetary property from the networked activity of individual players was the central insight of what came to be called Gaia Theory. As Margulis later wrote ‘Gaia is the regulated surface of the planet incessantly creating new environments and new organisms…. Less a single live entity than a huge set of interacting ecosystems, the Earth as Gaian regulatory physiology transcends all individual organisms’ (Margulis and Sagan, Reference Margulis and Sagan1986, p. 120).
Gaia Theory was controversial when it was first proposed, particularly because some saw it as introducing a teleological principle into evolution (Dawkins, Reference Dawkins1982), while others argued that there was no means for it to arise through natural selection (Doolittle, Reference Doolittle2017). We note that there still remain questions concerning the evolution and efficacy of biospheric feedbacks for producing a full planetary homeostasis (Kirchner, Reference Kirchner2002). Recent work, however, points to evolutionary mechanisms that may select for the global-scale negative feedbacks which could maintain such a system (Lenton et al., Reference Lenton, Daines, Dyke, Nicholson, Wilkinson and Williams2018).
Still, the basic principles of Gaia Theory, effectively repackaged as ‘Earth Systems Science’, now represent the cornerstone of modern approaches to Earth's evolutionary history. What Earth Systems Science took from Gaia Theory was its recognition of the biosphere as a principal driver of planetary evolution, as well as the profound role of collective microbial activity in shaping critical biospheric feedbacks.
The concepts of Biosphere, Noosphere and Gaia – as developed by Vernadsky, Lovelock and Margulis – are the foundations for what follow in our argument. Taken as a whole, they represented the crucial first coherent attempts to recognize that life and its activity (including intelligence) may best be understood in their full planetary context. Our goal in what follows is to focus on the ways in which a theory of planetary intelligence may be pursued and prove useful."
Excerpts
Definition of Planetary Intelligence
Frank A, Grinspoon D, Walker S:
"Our explicit definition of planetary intelligence is the acquisition and application of collective knowledge, operating at a planetary scale, which is integrated into the function of coupled planetary systems. One nascent example would be the global response to the planetary-scale crisis of ozonosphere erosion by CFCs. Another, still very much a work in progress, could be a global response to the crisis of anthropogenic global warming. However, we call these examples ‘nascent’ because, while they involve a global coordinated response to a potential existential threat, the decision-making is at the level of localized activities of individuals and governments. As wewill describe, a transition to global planetary intelligence should include a kind of intelligence that is more than the aggregate sum of the localized activities of life on smaller scales. We are interested in properties that exist at the scale of biospheres and/or technospheres (where technospheres are the aggregate planetary activity of technology; Herrmann-Pilath, 2018), and in their coupling to other planetary systems (e.g. geospheres), that are not apparent in individual organisms and subsystems comprising a biosphere or technosphere. Thus, the cognitive activity we are interested in must operate via feedback loops that are global in scale, coordination and operation. The concept of ‘human computation’ is one relevant example. Human computation includes examples where humans are computational elements in information processing systems, such as crowd-sourced activities like wiki editing or human-assisted AI (Michelucci et al., 2015). In addition, by defining planetary intelligence in terms of cognitive activity – i.e. in terms of knowledge that is only apparent at a global scale– we are explicitly broadening our view of technological intelligence beyond species that can reason or build tools in the traditional sense. We note that terms such as ‘knowledge’ and ‘cognition’ are usually reserved to describe individuals, but it is exactly our goal to push these concepts and determine in what sense they can apply to planetary-scale processes. We will clarify these points in the sections that follow. There are successive distinct domains where we wish to explore the operation, and effect, of planetary intelligence. We will argue that each relates to a different, but successive, phase of planetary evolution."
Planetary intelligence before technological species: biosphere networks
Adam Frank et al. : Once a species capable of constructing a technological civilization appears, intelligence by most definitions exists on a planet. As we will see, however, this does not imply it is meaningful to discuss the existence of a planetary intelligence as the dominant driver of planetary evolution in such a world. Life on Earth emerged almost 4 billion years ago. By 3 billion years ago, collectives of single-celled organisms existed in large enough quantities to begin affecting the coupled geophysical/geochemical systems (Lenton and Watson, Reference Lenton and Watson2011). The formation of methanogens, for example, is believed to have changed atmospheric chemistry sufficiently to alter the Earth's radiative properties and trigger the first global glaciation or ‘snowball Earth phase’. In addition, for the first two billion years of Earth's evolution, its atmosphere consisted primarily of N2 and CO2 with O2 acting only as a trace gas. It was the evolution of oxygenic photosynthesis by cyanobacteria that led to the atmosphere's Great Oxygenation Event (GOE) approximately 2.5 billion years ago (Catling, Reference Catling2014). The GOE made O2 abundant in Earth's biogeochemical networks with profound consequences such as allowing for far more energetic modes of metabolism (Lenton and Watson, Reference Lenton and Watson2011).
Microbes also play an essential role in Gaian and Earth Systems Science descriptions of planetary evolution through the establishment of feedback loops which maintain the planet in stable dynamic equilibria. Known and proposed examples of such feedbacks abound: climate regulation through biologically enhanced rock weathering (Zeebe and Caldeira, Reference Zeebe and Caldeira2008); the maintenance of O2 partial pressures below 30% through methane-producing microbes (Lenton and Watson, Reference Lenton and Watson2000; Berner et al., Reference Berner, Beerling, Dudley, Robinson and Wildman2003); climate regulation through cloud-albedo control linked to algal gas emissions (Charlson et al., Reference Charlson, Lovelock, Andreae and Warren1987); the biological transfer of selenium from the ocean to the land as dimethyl selenide (Watson and Liss, Reference Watson and Liss1998)
Given the critical role of microbes in establishing these feedback loops, when formulating questions of planetary intelligence one can first ask if microbes, or their communal networks, possess anything like cognition. In other words, do microbes or their collectives ‘know’ anything about the world, rather than just bumping into it? This leads us to ask what is meant by knowing or, more formally, to consider the nature of cognition across all forms of life. A succinct definition is given by Shettleworth (Reference Shettleworth1993) who sees cognition as ‘the mechanisms by which animals acquire, process, store, and act on information from the environment’. A more extensive definition is given by Lyon (Reference Lyon2015).
Biological cognition is the complex of sensory and other information-processing mechanisms an organism has for becoming familiar with, valuing and interacting with its environment in order to meet existential goals, the most basic of which are survival (growth or thriving) and reproduction.
There is now considerable evidence that bacteria exhibit a range of behaviours associated with cognition in the sense given above. Signal Transduction (ST), the most basic form of sense perception, is known to occur in bacteria in multiple forms allowing them to sense and respond to a wide array of environmental cues. Bacteria can also communicate through a process known as Auto-Induction where they stimulate changes in their genetic expression when certain environmental molecules reach threshold concentrations (Miller and Bassler, Reference Miller and Bassler2001). This is the basis of the much discussed process of bacterial quorum sensing where advantageous genetic changes in populations are induced at concentrations dependent on population density. Equally important was the discovery of rich social behaviours in species like Myxococcus xanthus (‘the primate of eubacteria’, Lyon, Reference Lyon2015) which has proven capable of structured, multi-dimensional swarming (Kaiser and Warrick, Reference Kaiser and Warrick2014), pack-like predation (Berleman and Kirby, Reference Berleman and Kirby2009), and the use of chemical cues to lure faster-moving prey (Shi and Zusman, Reference Shi and Zusman1993). Memory and learning, both bedrock conceptions of cognition, have also both been shown to be present in the bacterial toolkit of behaviours (Wolf et al., Reference Wolf, Fontaine-Bodin, Bischofs, Price, Keasling and Arkin2008).
From this perspective, there have been forms of cognitive activity (i.e. Vernadsky's cultural biogeochemical energy) on the planet for much longer than there have been animal nervous systems, and certainly far pre-dating the appearance of the genus homo. If the microbes which form planetary feedback loops can be said to collectively know things about their world then, perhaps, it may be possible and useful to ask if this knowing is integrated into higher scale, emergent behaviours which would represent planetary intelligence.
To see this, consider how the feedback loops which maintain Earth's O2 levels can be conceptualized (and modelled) as networks with information flow. Some habitable zone planets may also be capable of generating O2-rich atmospheres (Domagal-Goldman et al., Reference Domagal-Goldman, Segura, Claire, Robinson and Meadows2014) through a variety of processes in the atmosphere. Thus, O2 levels can vary due to purely geophysical/geochemical feedback loops. However, in the absence of a biosphere, these networks are not processing information in both the Shannon and semantic senses. On a planet without life, e.g. orbiting an M-star, O2 levels might be similar to those of an inhabited planet, but the O2 cannot act as a signal by geophysical/geochemical processes.
A biosphere, however, represents a complex network of feedback loops which can be seen as taking changing O2 levels as a signal. Such changes hold semantic information for the biosphere (Kolchinsky and Wolpert, Reference Kolchinsky and Wolpert2018) triggering responses that change the biospheric state. The presence of semantic information flows enables a biosphere to chart a contingent path through the available phase space of planetary states. Unique planetary states are selected that could not have been reached without its action. Perturbations in planetary conditions become significant and have meaning to the biosphere only within the context of the information represented by the existing state, which itself was reached through an evolutionary history. That is, like other biological systems at lower scales, we conjecture that the biosphere's evolution is ‘state-dependent’, with rules that emerge dependant on those states (Goldenfeld and Woese, Reference Goldenfeld and Woese2011; Adams et al., Reference Adams, Zenil, Davies and Walker2017). This is the dynamic we expect for planetary intelligence.
It is noteworthy that in today's biosphere there are semantic information flows, which act locally and yet can yield feedback and controls on larger scales. An obvious example is that information encoded in the arrangement of bases in a genome, which is minuscule in physical size compared to the planet, can nonetheless specify the control of metabolic pathways that shape global biogeochemical cycles.
In another example, arbuscular mycorrhizal fungi inhabit the root systems of 80% of land plant species (Simard et al., Reference Simard, Perry, Jones, Myrold, Durall and Molina1997). They are mutualistic symbionts that develop extensive, below-ground networks influencing uptakes and transfer of nutrients to their hosts. Because of their geographic extension, these networks may link contiguous plants to one another via their root systems. The global distribution of these symbioses is likely integral to understanding the present and future functioning of global scale biomes like forest ecosystems (Steidinger et al., Reference Steidinger, Crowther, Liang, Van Nuland, Werner, Reich, Nabuurs, de-Miguel, Zhou, Picard, Herault, Zhao, Zhang, Routh and Peay2019). Given their importance, and the apparent ability of these networks to direct nutrients to parts of the forest under stress, the question of self-recognition has been explored. Indeed, recent results show that the root systems of plants belonging to different species, genera and families may be connected by means of mycorrhizal networks, which can create indefinitely large numbers of below ground fungal linkages within plant communities (Giovannetti et al., Reference Giovannetti, Avio, Fortuna, Pellegrino, Sbrana and Strani2006). Thus, there may be pathways through which semantic information flows across these large-scale biomes. They, in turn, may be part of an emergent cascade to planetary scales of feedbacks and controls that could be considered cognitive in the autopoietic sense.
Finally let us consider the question of boundaries and signals. Before the GOE, O2 existed only as a trace gas in Earth's atmosphere. Through the collective action of cyanobacteria, the GOE was triggered and O2 became a principal component in Earth's biogeochemical networks. In terms of autopoiesis, one can argue that this led to the development of an ozone layer which became significant for the subsequent evolution of the biosphere. The thin band of atmosphere where ozone is maintained depends on the continued functioning of the biosphere. It may, perhaps, be seen as a simple boundary or photo-chemical membrane of the biosphere for which the signal is incoming sunlight. In addition, many planets have so-called ‘cold-traps’ in their atmospheres where the temperature switches from decreasing with height to increasing with height. On Earth, this temperature inversion occurs at a relatively low altitude, at the boundary between the troposphere and the stratosphere. Earth has not lost its oceans, as likely occurred on Venus, in part because rising water vapour condenses and rains back to the surface at the cold trap. The presence of oxygen in the atmosphere is a key reason for the location of the cold trap making it potentially another simple version of a signal-sensitive boundary that formed via the collective action of the planet's biota. While these examples are obviously highly speculative, they illustrate how the general principles we described in section ‘Theoretical Preliminaries’ may yield guidance in thinking about planetary intelligence.
Thus, we can imagine a transition in the evolution of a planet from one with an immature biosphere without strong networked feedbacks on the geospheres to a mature biosphere in which life becomes a dominant player in the evolution of the planet. Such a transition would be associated with the appearance of truly global feedbacks of semantic information, CAS behaviour and autopoiesis as shown schematically in Fig. 2. On Earth, this transition would have occurred in the Archean at its boundary with the Proterozoic."
From the conclusions
"Humanity currently sits at a precipice: our collective actions clearly have global consequences, but we are not yet in control of those consequences. A transition to planetary intelligence, as we described here, would have the hallmark property of intelligence operating at a planetary scale. Such planetary intelligence would be capable of steering the future evolution of Earth, acting in concert with planetary systems and guided by a deep understanding of such systems. If other civilizations that may exist in the universe also undergo such a transition, we would expect to see a marked difference in terms of the signatures of planets with sustainable, global intelligence versus those that have not transitioned to this phase of planetary evolution. Indeed, if planetary intelligence is a requirement for the longevity of planetary-scale civilizations, as we conjecture, we would expect most intelligence we observe in the universe to have gone through this transition.
A critical question is how viewing intelligence as a planetary scale process can help us adapt to and learn to harness the changes we are driving for our own long-term sustainability. Of course, the first question to ask is sustainability for whom? ‘Civilization’ at present is highly unequal in terms of those populations who have the greatest agency in effecting planetary change and those who are the most vulnerable to the consequences of planetary instabilities. Humans, or our descendants in the far future, may be very different than we are at present. Thus, the question of planetary intelligence is as much an ethical and moral one, as it is a scientific one. It implicitly assumes there is collective action that can operate for collective good, at the scale of global dynamical processes. As we have pointed out, what is best for individuals is not always optimal for collectives (e.g. cheating in evolutionary biology). Thus, the transition to planetary intelligence will have to overcome some of the same selfish challenges that evolution has faced repeatedly in the >3.5 billion year history of life on this planet. In fact, we can view the transition to global intelligence as a major transition in evolution, but one that must occur at the planetary scale (Furukawa and Walker, Reference Furukawa and Walker2018).
However, unlike other major transitions in the history of life on Earth, the transition to planetary intelligence is marked by lower-level components (e.g. us) who have some awareness of what is happening. By contrast, it is difficult to conclude that individual cells were aware of, or had a choice in, their joining together to enact multicellularity. Global transitions are already happening affecting almost everything about our daily lives, from what we eat and where, to our social behaviours and economic activity. Often the global features that regulate our behaviour as individuals are mediated by bottom-up action only, that is they are emergent properties of our complex global system. They are not necessarily steered at that global level however. Thus, we are in some sense partway through a major transition, where we have relinquished some of our individuality and behaviours, but we have not yet emerged on the other side where we are in it for the collective good.
To conclude, an exploration of an exploration of planetary intelligence can draw together three domains of study: the evolution and function of Earth's biosphere; the current emergence of the technosphere in the Anthropocene; and the astrobiology of worlds inhabited by technologically capable exo-civilizations. We hope that future work might articulate the properties and applications of Planetary Intelligence in more detail."