The Parable of Gaia's Grandchild

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As presented at the 2013 Spring Equinox Storytelling and Suishi Feast

Out on the plains, east of the Feos Mountains on the planet Piseri, the forest stretched for thousands of unbroken kilometers. The trees were so huge that every one was its own cosmos, a unique ecosystem built over the millennia by the complex interplay of thousands of species, some who colonize trees, some who only migrate through changing conditions in ways either subtle and brutish. Each change created and continued to create opportunities for other species and so, over time, each tree developed its own unique version of the greater ecosystem.

The most massive of these ecosystem-trees were also the most ancient, some so old that entire species had evolved and died out amongst their branches. The largest of their branches was so wide that an entire band of humans could have walked abreast comfortably along it, if there had been any human bands left on the planet. The trees were not just bigger, but had evolved many habits that gave them long life. Their branches grew struts that reached out and connected with other branches or rooted into the ground to form geodesic shells able to withstand the most violent storms. They stored rich tubers underground with enough energy to keep them through the worst winters. They built interconnected root systems that allowed trees to trade sugar for water or phosphorus for nitrogen across the entire continent so that they never went without the resources they needed for long. These networks were powered by wooden pumps, hearts in their heartwood which also raised sap far higher than transpiration had ever been able to do.

The oldest ecosystem-tree's last heart was failing. Its top had dried out and was leafless. But life sees death as an opportunity and the bigger the dying creature the bigger the opportunity; xeric mega-epiphytes had colonized it. Its top branches were so huge that they supported epiphytes that were up to thirty metres tall. Radiative evolution had found many marvelous uses for trees with hearts. Distant cousins of the ecosystem-trees, these mega-epiphytes sustained themselves on the dry branches by using their own heart pumps to compress and decompress gases. The cold newly decompressed gases were used to cool specialized leaves until they condensed water out of the air. These thick blue leaves dripped with moisture and were spotted with frost. The condensed water ran down deep bark grooves into waiting green basins at the bases of the mega-epiphytes. Thus these living basins became ponds from which the mega-epiphytes could collect water at need. At the same time, other leaves were kept warm by newly compressed gas. Photosynthesis was able to continue at a fast pace in the cold high-altitude air.

But life finds all concentrations of resources attractive. These artificial ponds were no different: tiny fish-like amphibians swam in them, feeding on plant matter. When a pond was disrupted the fish were still able to express amphibian genes, grow limbs and crawl off to find new ponds to live in, climbing many trees in their search for a suitable home before finding another pond and detaching their limbs to continue their piscine lives.

Piseri's biosphere was not isolated. The time of isolated biospheres had long ago passed and now space was alive with biological trade. Species moved back and forth from star to star by long slow trading of DNA and living beings amongst asteroid-sized leviathans which travelled between worlds. Millions of years before a tiny parasitic worm had found its way to Piseri and found the ancestors of the piscine amphibians to their liking. But every species that arrived from space created many new possible niches for native species. The piscine amphibians carried native worms with which they had formed a commensal relationship; Indeed, while the worms got food and a safe place to live from the amphibians, in return, they viciously attacked the alien worms, defending their hosts from the parasites. Both kinds of worms, alien parasite and native defender were present in the pond and each piscine amphibian.

Another species had found the alien worms useful. An amoeba whose ancestors had parasitized the native defender worms' ancestors had radiated to a new host, the alien parasite. Such a specialized species was very vulnerable to extinction--to be a parasite of a parasite is to occupy a very small niche indeed. But parasites often find it difficult to change hosts; the hosts have specific defenses which require specific adaptations to defeat and, once specialized, it is difficult to continue to interbreed with cousins who remain behind on other hosts. Opportunities to meet are rare and the resulting genetic isolation, combined with genetic drift, leads to permanent speciation. It was both cloud and silver lining, in that the amoeba had found a niche to which it had become supremely adapted. This was happening althrough the forest; The trees provided millions of niches that species could adapt to and the new species so formed provided millions more; the forest created diversity and used diversity to create diversity; an upward spiral of ever growing possibilities. Something was using those possibilities to store information for later retrieval.

Yet another species had a symbiotic relationship that was even more specialized and vulnerable. A species of bacteria lived on the skin of the amoeba protecting it from more generalized bacteria that might harm it. Bacteria are ubiquitous and their diversity is mysterious. Few understand how they interact, how many species there are or how widely they trade DNA. Even bacterial phages, viruses that attack bacteria, understand little of this.

Today one phage was attacking one of the bacteria which clung to the skin of an amoeba, in the gut of an alien worm. It attached to the skin of the bacterium and injected its DNA. The bacterium incorporated the DNA into its own. The virus had defeated the bacterium's defenses. Now the bacterium would produce copies of the virus until its cytoplasm was full of them and its membrane was stretched beyond its strength. Then it would burst and spew new viruses into the worm's gut. It seemed that the virus was victorious but, in truth, it was deceived. The virus had unwittingly carried a marker, a kind of message. The bacterium had responded to this marker by incorporated several dormant genes into every copy of the virus that it created.

These genes had been carried by the bacterium's ancestors for hundreds of millions of years. Now it was being called to send them out in the virus. The virus was generalized. It would attack many different kinds of bacteria and even different kinds of plants. Somewhere an ecosystem-tree, immune to the viruses' attack would accumulate these genes and use them to create seeds for a new kind of mega-plant. This new kind of plant would create further seeds and have the ability to throw them into space. Each seed would be carrying enough genetic information to grow whole ecosystems. Markers were spreading from virus to bacterium to virus all through the forest; Piseri was Gaia's grandchild and she was preparing to have children of her own.

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