key: cord-0852587-chk7z8u9
authors: Doolittle, W. Ford
title: Evolutions’ next major transition
date: 2020-06-28
journal: Curr Biol
DOI: 10.1016/j.cub.2020.06.079
sha: 0863d2854a3a6aac698c4ab6b8eb50df726c9446
doc_id: 852587
cord_uid: chk7z8u9

Much discussion about the impact of the Covid-19 pandemic and whatever emerges as the 'new normal' has been psychological or political in nature, but there is a more inclusive evolutionary biological context in which we might understand it, ourselves, and our responsibilities to the planet.

Steven Jay Gould, probably the most influential mid-century theorist for the public and practicing biologists alike -and a champion of "contingency" -was particularly down on the notion of progress. He wrote that it "is a noxious, culturally embedded, untested, nonoperational, intractable idea that must be replaced if we wish to understand the patterns of history" (2) . In his Wonderful Life (3) he likened the evolution of life's complexity to a sort of random "Drunkard's Walk". Life started very simply of course and since complexity space is large, wound up some place more complex, but there was no driving force favoring the formation of complex organisms like ourselves from simple ones like bacteria. There was only contingency, he held, and most of us went along with him.

Maynard Smith and Szathmáry's book changed this thinking insofar as it described evolution as an almost inevitable series of major events (or sometimes similar major events occurring in parallel in different lineages) representing a subsuming of the evolutionary interests of lower-level units by higher-level collectives comprising several or many such units (Fig. 1) . This was thus indeed a kind of progressive ratchet, moving evolution towards ever higher levels of complexity and sophistication, by nesting individuals within collectives, as new, composite, individuals. A sacrifice in independence or reproductive "selfishness" of the units to the collective was a new evolutionary principle, Maynard Smith and Szathmáry argued, writing that "One feature is common to many of the transitions: entities that were capable of independent replication before the transition can replicate only as part of a larger whole after it".

used as examples the incorporation of genes into chromosomes, of cyanobacteria and free living respiring bacteria plus their ultimate hosts into eukaryotic cells, the incorporation of individual lineages into species through the invention of inter-lineage recombination (sex), and the origin of multicellular organisms from unicellular organisms (1). At transitional stages there was a conflict of evolutionary interests to be overcome, and sometimes the higher-level entity still shows only what Maynard Smith and Szathmary called "contingent irreversibility". That is, some genes can free themselves from the yoke of control by chromosomes (becoming transposable "jumping genes" or even viruses), some sexual species can revert to asexuality, and sometimes cellular lineages can start to replicate independently of the controls imposed by the multicellular organism of which they are part: we call that cancer.

Sometimes external biological or abiotic environmental stressors might be imagined to have established conditions favourable to a transition: competition between different individual gene families might have favoured their getting together as chromosomes, increased atmospheric oxygen might have driven the origin of nucleus-containing cells, competition with parasites might have favoured the evolution of sex, and the advantages of size and the evolutionary opportunities offered by cellular differentiation could have promoted the transition to multicellularity, which has occurred several times in several lineages.

There were also several even higher-level transitions having to do with social organization. Maynard Smith and Szathmáry saw the origin of colonial species (bees and ants for instance) from solitary individuals, and of primate societies as examples. Cultural theorists have gone further, seeing a progression from bands (tribes), to chiefdoms (kingdoms) to nations and partially successful national alliances like the League of Nations or the UN, while the evolutionary ecologist Stephen Stearns suggested more than a decade ago that we are now "stalled part way through a major evolutionary transition from individual to group" (4). Indeed the irreversibility of cultural transitions is still highly "contingent" in Maynard Smith and Szathmáry's sense, and stress brings out conflicts between levels, which we might see now in the polarization between populisms of the left and right at the expense of national unity around the world.

The current pandemic is a stressor of unguessable strength and unknowable consequences: most of us cannot really get our minds around the potential impact. Political pundits have speculated about the new normal, and much of this speculation boils down to realizing that there are two main possibilities. Either we revert to populist nationalisms and even racial tribalisms or we unite as a international collectivity, addressing not only Covid 19 but climate change and income inequality, these stressors now combining in unpredictable ways, even as I write. An essay by the ecological economist Simon Mair in The Conversation, now circulating on the internet (5), further imagines a four-part grid (Fig. 2) , the two dimensions of which are response (centralized-to-distributed) and value (economics vs the protection of life). State capitalism and state socialism are the two centralized responses and barbarism and mutual aid are the distributed outcomes, and of course any real response will be a mix of the four, unpredictable as yet. Most first-world governments are at the moment drifting towards state socialism, but it's not clear how much economic damage can be sustained before state capitalism resurges as it seems now to be doing in the US, and Hobbesian barbarism is always a horrible possibility -especially if these two versions of centralization are seen as inevitably in conflict.

Though we can look at all this politically and economically, there is as well the broader evolutionary biological perspective provided by Maynard Smith and Szathmáry. If what has happened in evolution (either biological or socio-cultural) is a sequence of subsummations of lower entities into collective higher ones, entailing inter-level conflict and a sort of contingent irreversibility, then that may be happening once again, and again under stress, with an uncertain outcome. We are at the cusp. Maybe this biological perspective is even, stepping back, a better and more informative, longer-term view. Mair's two favoured outcomes might correspond to the transitions represented by the origins of eukaryotes, in which evolutionarily separate but symbiotic (mutualist) entities fused into one individual with "top-down" control (Mair's "State Socialism"), and the formation of ecosystems, sustained by the joint activities of many species ("Mutual Aid"). Either would entail our species functioning at a higher, collective level: a major transition in the making. This is not just metaphorical thinking. One way to survive this crisis, and maybe climate change and income disparity, is to start acting as the single species that we are, rather than as the individual tribes or nations that we comprise. In fact we are a species embedded with and dependent on many others and so this transition is further unique in the following way. Because we are conscious agents, the collective of all species on Earth now becomes conscious, potentially capable of directing its own future. Tim Lenton and Bruno Latour stressed this in a recent article in Science (6), writing that … According to Lovelock and Margulis's Gaia hypothesis, living things are part of a planetary-scale self-regulating system that has maintained habitable conditions for the past 3.5 billion years. Gaia has operated without foresight or planning on the part of organisms, but the evolution of humans and their technology are changing that. Earth has now entered a new epoch called the Anthropocene, and humans are beginning to become aware of the global consequences of their actions. As a result, deliberate self-regulation-from personal action to global geoengineering schemesis either happening or imminently possible. Making such conscious choices to operate within Gaia constitutes a fundamental new state of Gaia, which we call Gaia 2.0. By emphasizing the agency of life-forms and their ability to set goals, Gaia 2.0 may be an effective framework for fostering global sustainability.

Covid 19 is a consequence of human action. The larger our population and the more we invade the habitats of other species the more frequent will be such zoonotic diseases, and the more global are our travels the quicker these diseases will spread (7). It's not that Gaia is deliberately punishing us. But it is that we still behave as if nations were our most inclusive units, and economicsnot protection of life -was our purpose. We must "re-biologize" our thinking. We need to recognize that we are all part of one species and that this species is just one among many, singular only in being uniquely capable of understanding and changing the future of all life on the planet. If we can accomplish that, we will have witnessed the last (for now) and most inclusive (for now) of the Major Transitions in Evolution. Whether such a biosphere-wide subsummation of evolutionary interests by a centralized bio-cultural entity, if it happens, will look more like Mair's "State Capitalism" or his "State Socialism" is anybody's guess. Perhaps an intermediate stage corresponding to a more robust form of his "Mutual Aid" is the best we can or should hope for now.

At each transition, entities capable of independent reproduction (and thus with their own evolutionary trajectories) combine to produce collectives that reproduce and have new trajectories. In some cases, the transition is incomplete and lower level units can subvert collective interests (as in cancer). The social transition that Covid 19 might facilitate is as yet very incomplete. Arrow is time. 

The Major Transitions in Evolution

On replacing the idea of progress with an operational notion of directionality

Wonderful Life: the Burgess Shale and the Nature of History

Are we stalled part way through a major evolutionary transition from individual to group

What will the world be like after coronavirus? Four possible futures. The Conversation

Drivers, dynamics, and control of emerging zoonotic diseases