Thursday, January 15, 2009

The Medea Hypothesis the dark side of the Gaia Equation

The utter vulgarity of the herd of men comes out of their preference for the sort of life a cow leads.

Aristotle
Ethics

In an interesting article doing the rounds we see another perspective of the nice homogenous world told to us of the distant pre anthropic past..Where climate was stable and an a multitude of fauna and megafauna inhabited the earth in some peaceful coexistence.

A nice story but far from the reality of the hard and fast facts of evolutiom

WHEN WE LOOK at nature, it has become commonplace to see a fastidiously self-regulating system at work: wildebeest trim the savannah grasses, lions cull the wildebeest herds, and vultures clean the bones of both. Forests take in the carbon dioxide we exhale, use it to grow, and replace it with oxygen. The planet even has a thermostat, the carbon cycle, which relies on the interplay of volcanoes, rain, sunlight, plants, and plankton to keep the earth's temperature in a range congenial to life.

This idea of nature's harmonious balance has become not just the bedrock of environmental thought, but a driving force in policy and culture….

…According to the paleontologist Peter Ward, however, nothing could be further from the truth. In his view, the earth's history makes clear that, left to run its course, life isn't naturally nourishing - it's poisonous. Rather than a supple system of checks and balances, he argues, the natural world is a doomsday device careening from one cataclysm to another. Long before humans came onto the scene, primitive life forms were busily trashing the planet, and on multiple occasions, Ward argues, they came close to rendering it lifeless. Around 3.7 billion years ago, they created a planet-girdling methane smog that threatened to extinguish every living thing; a little over a billion years later they pumped the atmosphere full of poison gas. (That gas, ironically, was oxygen, which later life forms adapted to use as fuel.)


An indeed it is this well understood.and is also an evolutionary catalyst.. The living world is nowadays subdivided into three ”domains” or main organismal groups, i.e. Archaea, Bacteria (eubacteria, or just bacteria), and Eukarya (eukaryotes, which comprise all organisms known 200 years ago, and many others, plants, fungi, animals, and people). Photosynthesis has arisen only in the domain Bacteria. That plants, too, can carry out photosynthesis is because the precursors of plant cells have combined with bacteria

The Evolution of Photosynthesis and its Environmental Impact(extract Bjorn and Govindjee)chapter12

When we think about how photosynthesis has affected our environment, we may first
remember that it has produced the oxygen we breathe, and (directly or indirectly) the
food we eat. But the impact of photosynthesis is much wider. The oxygen produced
by photosynthesis has also given rise to the ozone layer, which protects the biosphere from the ultraviolet-B radiation from the sun The fossil fuel,has been produced by photosynthesis in times past. The sequestration of carbon from the atmosphere has given us a human-friendly climate,.We must not fall into the trap of believing that photosynthesis has always resulted in a good environment for the inhabitants of our planet. The free oxygen is still a hazard for our own cells, and even for the chloroplasts producing oxygen. Photosynthesis has not always had a friendly, Gaia-like influence on inhabitants of the Earth. When oxygen first started to accumulate, it almost certainly killed off a large part of the terrestrial population by direct poisoning. It was even a hurdle to the producers themselves. Many of the cyanobacteria (as many other bacteria as well as archaea) carry out nitrogen fixation by means of nitrogenase. Nitrogenase is extremely sensitive to oxygen and easily inhibited by it, and organisms had to invent various methods for protecting the nitrogen fixing enzyme from oxygen. Some of the filamentous forms developed special cells (heterocysts) for a special kind of photosynthesis, which fixes nitrogen using PSI only, and does not fix carbon dioxide or evolve oxygen. From morphological fossils it has been deduced that this arrangement is 1.5 Ga old. In modern cyanobacteria there is a strict correlation between occurence of heterocysts and of akinetes.Before cyanobacteria evolved, the oxygen content of the atmosphere was below 10-5 of the present. The initial effects of photosynthetic oxygen production on climate were disastrous. Before the oxygenation of the atmosphere the earth was kept comfortably warm (too warm for the human taste) by not only a high atmospheric content of carbon dioxide, but also by another greenhouse gas, methane. When oxygen arrived, methane was first oxidized to carbon dioxide by an emerging new group of microorganisms. Then also the concentration of carbon dioxide was drastically lowered by cyanobacterial assimilation. This led to a sharp temperature decrease and a glaciation which lasted for about 70 million years, between 2.32 and 2.22 Ga ago. Since traces from this time of glaciation (the Makganyene glaciation) are found near the ancient equator, some scientists believe that the whole globe became covered with ice and snow during at least part of this time. There was what has been called a ”snowball earth” The ice cover prevented silicate weathering, a process that consumes carbon dioxide, and continuing volcanism increased the carbon dioxide content again and eventually put an end to the long ice age. In the meantime the hydrothermal vents at the bottom of the sea had spewed out nutrients at a rate which could not under the icy conditions be matched by consumption. Therefore, many cyanobacterial nutrients were abundant at the end of the glaciation, but probably not all.


There is also another process based on the dictum of you cant beat theem join them assimilation as we discussed here.

“Let us imagine a palm tree, growing peacefully near a spring, and a lion hiding in the bush nearby, all of its muscles taut, with blood thirsty eyes, prepared to jump upon an antelope and to strangle it. The symbiotic theory, and it alone, lays bare the deepest mysteries of this scene, unravels and illuminates the fundamental principle that could bring forth two such utterly different entities as a palm tree and a lion. The palm behaves so peacefully, so passively, because it is a symbiosis, because it contains a plethora of little workers, green slaves(chromatophores) that work for it and nourish it. The lion must nourish itself. Let us imagine each cell of the lion filled with chromatophores, and I have no doubt that it would immediately lie down peacefully next to the palm, feeling full, or needing at most some water with mineral salts.”

(Konstantin Sergeevich Mereschkowsky (1905)


We see this within all humans now with our mitochodria developed form other phenotypes.Indeed around 50% of yours and my drymatter by weight is mitochodria,and we may even have some martian mitochondria in us having arrived on a meteor as we discussed earlier but that is another story.

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