Geology Reference
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is the ability to swap bits of DNA, much as you or I sell or buy second-hand clothes at
charity shops, only more so. Evolutionist Lynn Margulis and writer Dorion Sagan use a
powerful analogy that beautifully illustrates this bacterial capacity for gene exchange. If,
by some magic, your body could swap DNA as bacteria do, copies of your DNA would
leak out of you profusely as you swam around in your local swimming pool. If you were
blueeyed, the pool water would teem with multiple copies of blue-eye genes that had
leaked into the water across your skin. Any brown-eyed swimmer plunging into the pool
after you would easily absorb your genes and would emerge from their swim with start-
ling blue eyes much like yours. Margulis and Sagan provide a further analogy. If we had
the gene-swapping abilities of bacteria, then by merely smelling roses and inhaling the
rose-smell gene we would smell like roses ourselves, or we could develop tusks just by
spending a little time in close contact with elephants.
Oxygen-producing photosynthesis, one of the most astonishing of all bacterial meta-
bolic accomplishments, may well have been invented by a single ancestral bacterium
that spread the innovation by means of the 'open source' genetic exchange that we have
just explored. We can illustrate this with a little story. Imagine that some 3,000 million
years ago, during the Archean eon, there was a microbe named Suria who lived in the
surface of the Earth's ancient ocean, swirling about in the great eddies which the wind
made as it stirred up the waters. Life was already well established, and the air was full
of methane, for this was long before the time when oxygen became abundant in the air.
Suria, like many of her brethren, had been harvesting energy from the sun by splitting
hydrogen sulphide gas from the depths into hydrogen and little globules of yellow sul-
phur, which she spat out into the sea. Then by some trick of the light, or by some re-
markable coincidence of metabolism or genetics, a sudden but rather small change oc-
curred deep in the tumultuous and beautifully orchestrated biochemical realm where the
chemical beings which constituted her physical form played out their fantastic chemical
intrigues, assassinations and love affairs. Suddenly, down in those depths, Suria's mo-
lecules configured themselves into a new way of dancing with sunlight and she was able
to extract the life-giving hydrogen from water, H
2
O, rather than from the pungent hydro-
gen sulphide gas all around her. Now she secreted oxygen rather than sulphur, and the
world was forever changed. Suria, in creating 'oxygenic photosynthesis', had become
oured photosynthetic pigment. This was a fantastic achievement, and Suria, abiding by
the microbial code of reciprocity, released small fragments of the genetic text bearing
the secret of this new discovery into the sea around her. Soon, her immediate neighbours
had taken up the message, and they too began to make oxygen and hydrogen from wa-
ter. The recipe for oxygenic photosynthesis spread rapidly through the global microbial
community, and very soon the superabundance of water made it possible for the photo-
