A few days ago, in comments for another post, I threatened to write somethong about Oliver's chat with James Lovelock.

Jim is, among many other things, a master of analogy, and I was struck by a new one that he was road testing – one that mixes catastrophe and optimism in a way that chimes with his new book, but which is not I think spelled out there.

The analogy is between oxygen and intelligence, and the creatures — cyanobacteria and humans — which brought these new and terrible entities to the world. In both cases, there were precursors. There are non-biological processes which produce free oxygen, and there is intelligence of various sorts elsewhere in the animal world. But in both cases there was at a specific point a quantitative shift so huge as to be qualitative and then some. Cyanobacteria really did overturn the biosphere 2.45 billion years ago, and they and their descendents have shaped it ever since; human intelligence has done so too, from the Pleistocene die-offs onwards.

Lovelock’s point is that an evolutionary breakthrough in a single form of life can have global consequences and that such a breakthrough can be — probably must be — highly destabilising, even catastrophic. The presence of free oxygen was a huge change in the terms on which life prospered on the earth, since everything that came before was based on anaerobic metabolisms: many niches and perhaps species were wiped out. Similarly, intelligence of the sort demonstrated by humans is proving far from benign on a global level, with ever increasing stress on ecosystem services and, as with oxygen, wholesale rewiring of various biogeochemical cycles.

Yet in time, for all the disruption it caused early on, oxygen became the basis of something far grander than what had come before. The amount of free energy available to the biosphere increased spectacularly, with reasonable levels of oxygen facilitating complex multicellular life in way which may well be impossible in an anaerobic world (Catling et al [pdf]). All the life you see and care about is made possible by that oxygen (though not all the life that you depend on — at the deep biogeochemical level the microbes, including the anaerobic ones, still rule). Similarly Jim suggests that, in time, intelligence may make possible a more wonderful planet in ways we can hardly guess at today and bring forth a “wise, thoughtful world”. . .

And as an analogy, Jim takes it one intriguing stage further. While cyanobacteria still abound, they are no longer the sole source of oxygen, nor even the dominant one. The cyanobacteria not only made new life forms possible — they also incorporated theselves into them, in the form of chloroplasts. The ability to make oxygen was disseminated into creatures radically unlike the original cyanobacteria — into kelp forests and elm trees and cactuses and camelias. Perhaps, Jim suggests, the same is true of intelligence — that its destiny is to be spread far beyond the species in which it first originated, into new achitectures of life and thought.

It's an analogy, and Oliver quibbles with parts of it. Another quibble may be that it wasn't that the evolution of cyanobacteria caused the oxidation event, it was a consequence of geological change.

Nickel exists in today's oceans in trace amounts, but was up to 400 times more abundant in the Earth's primordial oceans. Methane-producing microorganisms, called methanogens, thrive in such environments, and the methane they released to the atmosphere might have prevented the buildup of oxygen gas, which would have reacted with the methane to produce carbon dioxide and water. A drop in nickel concentration would have led to a "nickel famine" for the methanogens, who rely on nickel-based enzymes for key metabolic processes. Algae and other organisms that release oxygen during photosynthesis use different enzymes, and so would have been less affected by the nickel famine. As a result, atmospheric methane would have declined, and the conditions for the rise of oxygen would have been set in place.

The researchers found that nickel levels in the BIFs began dropping around 2.7 billion years ago and by 2.5 billion years ago was about half its earlier value. "The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event," says Papineau. "And from what we know about living methanogens, lower levels of nickel would have severely cut back methane production."

What caused the drop in nickel? The researchers point to geologic changes that were occurring during the interval. During earlier phases of the Earth's history, while its mantle was extremely hot, lavas from volcanic eruptions would have been relatively high in nickel. Erosion would have washed the nickel into the sea, keeping levels high. But as the mantle cooled, and the chemistry of lavas changed, volcanoes spewed out less nickel, and less would have found its way to the sea.

Perhaps (as Oliver suggests) "oxygenic photosynthesis was around for a long time before oxygen was able to build up in the atmosphere". It's presence is masked in the geologic record since it reacted with abundant methane.

To me, this suggests a different analogy than Lovelock's. It isn't that an evolutionary breakthrough brought catastophic change for the old order so much as that the decline of the old order revealed change that already occured but had not thrived. Photosynthetic bacteria were a response to catastrophe, not a cause, and so perhaps intelligence can be seen in a similar light. Perhaps the catastrophe that suddenly ended the age of giant reptiles allowed mammals to become more dominant in response, and intelligence is a way to evade a repeat of such a catastrophe. Still, it's a quibble since it ends up in the same place.

Perhaps, Jim suggests, the same is true of intelligence — that its destiny is to be spread far beyond the species in which it first originated, into new achitectures of life and thought.

It’s an idea that may sit uneasily with Lovelock’s current pessimism, which sees human activity as bound to lead to a fairly massive die-back. But it flows easily from the tradition of thought that Lovelock (and Freeman Dyson, and the late Arthur C. Clarke) drank from as a young man, a tradition that combines a respect for thermodynamics (there’s a free-energy/information level to Lovelock’s analogy that would probably be interesting to tease out) with a cosmically-contextualised yearning for transcendence.