Conversations with a Soul by McArthur Tom

Author:McArthur, Tom [McArthur, Tom]
Language: eng
Format: mobi, epub
Published: 2013-02-19T18:30:00+00:00

4 billion years ago ours was a dead planet. Simple life forms evolved about a billion years later, then somewhere about 500 million years after that, the first players emigrated from the sea – plants, vegetation, growing rooting germinating sprouting things that prepared the earth to receive the earliest known creatures.

Before about 480 million years ago, the continents were lifeless save for thin crusts and varnishes of bacteria. Green algae growing near the coasts began to creep into inlets and estuaries, where rivers carried fertilizing loads of weathered minerals and dead microbes. The algae moved into shallower waters and evolved a thick skin that protected against longer and longer exposure to the open air, until they no longer had to be submerged. They became land plants. Soaked by sunlight, they evolved into low mossy mats and then ground hugging weeds . . . new species evolved, slowly at first, developing roots and associations with underground fungi to extract food and water from the ground, and hard tissue to hold the botanical weight high. When the plants died their corpses enriched the estuaries and inlets with nitrogen, phosphorus, and other scarce elements, making it easier for succeeding generations to grow. Invertebrates emerged from the water, beginning with millipedes, 450 million years ago, and then followed by insects, spiders, scorpions, worms and mites; they began to root through the thickening soil and nibble the stems.56

I stood there as the kelp washed ashore, transported back through time in my mind and imagination, witnessing a process that has been going on for millions of years!57

Somewhere around 385 million years ago lobe fined fish, of which the celebrated coelacanth is a distant cousin, migrated into wetlands and marshy inlets, and another frontier was breached.

Not shaped for long, deep-ocean swims like sharks and tuna, lobe-fins were better suited for sudden bursts through sludgy water. One of the risks of life on the coasts was the sudden drop in the oxygen caused by blooms of bacteria feasting on organic matter in shallow water, and sucking up the gas for themselves. But with lungs the lobe-fins could get their oxygen elsewhere. The fossil record suggests that lobe-fins thrived in these places. Evolving into enormous forms, they feasted on the galaxies of small fishes that in turn fed on the invertebrates that lived in the muck. Their limblike fins even let them move along the bottom of the lagoons, and in shallow water they might have pushed up with their front fins to breathe.58

Perhaps, some amphibious creatures may even have started to colonize the land through their fertilized eggs. Washed into estuaries and lagoons they lay in shallow water until they hatched.

Yet the migration was not simply from sea to shore but also from shore to sea!

Mammals that breathed oxygen yet live in the ocean, present us with an anomaly. What are oxygen breathing creatures doing in a world where the inhabitants were designed to filter out oxygen in the water? Palaeontologists and their evolution-investigating cohorts came to believe

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