This eight-legged gummy bear is a tardigrade, a tiny animal found everywhere from the antarctic to the equator, the bottom of Marianas Trench to the summit of Everest. Tardigrades survive naked exposure to the vacuum of space and pressures three times greater than the bottom of the sea, freezing in liquid nitrogen, boiling in oil, and pH and radiation extremes thousands of times greater than any other animal. They are omnivorous, reproduce with and without sex, and in the lab have remained viable for more than a century without food and water.
Tardigrades are found fossilized in Cambrian rocks more than half a billion years old. They are their own phylum of life, unrelated to all other multicellular life except nematode worms. We’re just beginning to understand tardigrade biology but we know nothing of the evolutionary forces that produced such strange little beasts.
To begin to answer that question, consider a less outlandish life form, something more on the human scale. Australian gum trees – eucalypts. Eucalypt leaves continuously exhale an aerosol of flammable oil and every few years the aerosol combusts to render entire forests to a layer of ash. The ash makes soil suited to spread eucalypt seeds and suckers. But it’s not just the eucalypts that burn. Effectively, the eucalypts exploit fire as a method of predation on other forest species.
Lao Tzu chapter 1 sees life as neither an aspect of the form of fire, nor of the pattern of eucalypt DNA, but of the repeating cycle of form and information. Of fire and DNA. The information in the genes of eucalypts co-evolved with the fires, expressing the form of fire to spread the information in the Eucalypt genes.
Well then, what form spreads the information in the genes of Tardigrades?
Fire only became possible on Earth with blue-green algae. The oxygen wastes of those bacteria formed a reactive toxin that came to destroy most life forms that inhabited Earth prior to their evolution. Like eucalypts with fire, blue-green algae co-evolved with ambient oxygen to render other organisms into nutrients enabling propagation of their genes.
Biologists call this event the Oxygen Catastrophe. It took millions of years, but there came a day where the atmosphere held too much oxygen for the archaea to tolerate. All over the world, methanogenic bacteria went green or went extinct. The sky turned blue and one fine day there sparked the very first atmospheric oxygen fire.
In math, any sudden transition between two different system behavior is called a catastrophe. Catastrophes occur in any entropic process and on all scales from the fall of leaves and pulse of organs through the generation of organisms to the extinction and evolution of species. Counting the oxygen catastrophe, the ecosphere has had at least six periods of global catastrophe with the seventh currently under way.
The solar system is subject to still more violent catastrophes. And our system is one of hundreds of billions of stars in one of hundreds of billions of galaxies. Stars derive energy by fusing hydrogen atoms into heavier atoms, and when they runs out of fusible hydrogen they swell or explode. Then waves of gas, dust and rubble expand outward to impact surrounding dust clouds, eventually forming a new generation of stars.
On a human timeframe that’s a distant event. But in astronomical terms our sun is 3 stellar generations removed from the original formation of the Milky Way Galaxy. It is a young star in an old galaxy. The Milky Way is a hurricane of burning dust full of stellar catastrophes that can propagate a tardigrade to reach another world. On cosmic timescales, we should expect that our young solar system and all solar systems are now lousy with organisms that evolved somewhere else.
We see signs of this “panspermia” process. A third of observable interstellar dust matches the visual and infrared signature of freeze-dried bacteria. Clumps of bacteria have been detected at heights in the stratosphere that cannot be reached by Earthly bacteria. While the sun’s UV radiation sterilises many microbes, we know numerous species of hardened bacteria exhibit tolerance to ionising UV and even Gamma radiation.
Interstellar journeys are accessible even to non-hardened microbes during a sun’s red-giant phase when its sterilising UV and cosmic rays diminish. And solar radiation pressure is sufficient to expel microbes into interstellar space. Entering a young solar system such extra-solar life forms inevitably accrete to comets in the Oort cloud, sheltering from radiation within the comets’ liquid centers. Jupiter, Saturn and other gas giant planets contain vast hydrocarbon cloud belts that offer hospitable cradles for the incubation of such forms of life.
Carl Sagan famously imagined “floaters“, gas-filled blimps swimming like jelly-fish through dense oceans of cloud on gas giant planets. If floaters were to reproduce via spores as tiny and sturdy as our tardigrades, these could hitchhike on grazing comets to journey from one world to another. And Sagan’s “sinkers”, tiny forms feeding on nutrients suspended in those clouds, would have to exhibit the pressure-tolerance of tardigrades. This is not to say that tardigrades are his sinkers, but there may be many members of the Tardigrade phylum better adapted to gas giant worlds. Evolution would favour the development of tiny extremophiles suited to any and every planetary condition.
So you would expect that once the newly oxygenated surface of Earth had stabilised to the point of supporting complex life, there would be a sudden and unique diversification of creatures in the fossil record as the clade of pre-evolved extraterrestrial spores took hold. We would expect tardigrades to date from this point in time. And indeed this is exactly what we find – it’s the Cambrian Explosion.
We have no instruments to detect extra-terrestrial microbes in transit. But it is inevitable that comets derived from encounters between astronomical bodies carry multicellular life away. The most common Earthly food of tardigrades – lichen and fungi – survive space travel. Earth-born meteorites carry viable plant seeds and animals. Accreting to comets and asteroids, these would naturally seed other rocky worlds with life. Meteorites originating on Earth may be tiny spaceships. But life may do more than travel between the stars. It may play an essential role in the creation of the stars.
On far larger scales than planets, ionised gas mixes with the molecular clouds generated by exploded stars. The fundamental processes that cause stellar nebulae to condense into clusters of new stars are driven by the physics of entropy and gravity, but their clumping behaviour and motion are influenced by the distribution and evolutionary dynamics of self-organising, self-reproducing helices of dust and plasma. And these dynamics are driven by the forms of the particles making up the interstellar dust.
In earthly clouds airborne bacteria have co-evolved to promote catastrophic precipitation of rain and snow. Earthly forests would wither without the information in the genes of airborne bacteria propagating in the form of rain drops. Likewise genes that influence the shapes of the freeze-dried microbial components of cosmic dust-helices will evolve to promote the form of star systems favorable to their own reproduction. On an interstellar scale, the evolutionary forces embodied by these bacteria could do more than precipitate rainfall – they can cause the creation of water itself.
Just as with eucalypts, evolution favours clades of interstellar life forms whose aggregate promotes conditions amenable to their own reproduction. So we should expect that when we look into the night sky we will see the same forms – bubbles, membranes and vortices – fractals of the forms that occur in an Earthly pond. The forms of stars are generated by the same process and a superset of the same creatures we find in any Earthly pond.
It is our anthropic conceit, exemplified by Sagan’s blue dot, that causes this simple fact to come as a surprise. We are not tiny creatures confined to a pixel. Our evolving universe is not a sterile, piecemeal, or haphazard continuum. The life that expresses us runs through every pixel of these pictures, a cosmic ecosystem with scale symmetry binding it from the astronomic to the nanoscopic.
A pre-scientific author could hardly have concerned himself with the co-evolution of stars and microbes. But as a non-local poem that has co-evolved with humanity over thousands of years, Lao Tzu’s words apply very well in this context. The evolving poem concerns life, not as a taxonomy of dusty butterflies pinned to a board, but as a universal ecosystem that expresses itself as butterflies, tardigrades, stars, and you.
The stage so set, we’ll move on. Chapter 2 has traditionally been translated as a laundry list of virtues. Unlocking it, we find instead the central concern of the poem. Co-evolving with this boundless, growing, subtle and catastrophic fire-froth of life, what part is played by a lonely human being?