What follows here is an entirely factual account of a
photoreceptor cell belonging to my eye. It has been on a remarkable journey,
much like the rest of the cells composing my being; indeed, I am the cumulative
product of many, many wonderful journeys of all types. This was of course,
exactly how the entire process took place. I know because I asked, and this is
was the cell said:
The
Beginning could have happened in anyone’s universe, but it didn’t.
Before charts and tables,
before catalogues and clocks, a Nothing became quite suddenly Everything. A
flood of energy rushed through the newly crowded emptiness; an elegant violence
sweeping the dust clouds into whirlwinds around each other.
Within this broiling stew
of chemistry was a particular particle of a star; the wispy spirit of shining dust,
clumping like silent snowflakes to the burning velvet fabric of a new universe.
This world was crowded, busy, bustling with action, but with each passing
moment, it grew colder and colder and farther apart. Novel things were
happening in this universe; gasses condensing into balls of fury, magnetic
fields arching into regular patterns, planets falling into position. Novel
things were happening, but not right here. Not yet. The stardust moseyed on. What
are the odds that our particular piece of stardust would, after waiting
patiently for so long, be picked up by a passing barrage of rock? Probably unclimatically
high. Our little hitchhiker bummed past woven galaxies, just beginning to spin.
It was a very special time, but it didn’t realize this, or even particularly
marvel at the novelty; it hadn’t yet found its purpose. And quite suddenly, it
was distracted.
This barrage of rock, a
veritable rainstorm of rock, was plummeting into a planet’s foaming surface; hurling
with such force as to be incinerated on impact. Or, well, almost incinerated.
The little piece of stardust plunked into this warm primordial stew and sank farther
and farther, gently into its murky depths, rich with nutrients, rich with
pieces, rich with possibilities. The spark fell and it fell into Place: the
last piece in a structure that had been almost completed maybe only a handful
of times before, maybe millions of times, but still it remained, now completed.
The Beginning of a universe of a different sort. This structure was novel,
different from anything the young planet had ever before known. This structure
was Compelled. This structure, the first ever, Wanted.
And it was lonely.
This first Being, knowing
no thing as great and as well put together as itself, soaked in the nearby
resources and created another Being in its image. This second Being was filled
with much the same compulsion as the first, and it too copied and copied and
copied. There was so much world to be filled!
And so it went, copy after
copy after living Being. But something was different… each time, each Being,
each copy… they were not each done perfectly. The changes were little at first,
slight errors in transcription, small modifications in chemical structures, but
with time, they accumulated. New cells moved. New cells swam and ate and needed
other cells to reproduce. New cells were hungry. The changes didn’t stop. With
each new altered copy and altered copy of that altered copy, the Beings became
completely unrecognizable from the First. They began to share, passing
information only between those that resembled themselves. They divided into
clans. The world around them changed too and some Beings survived better and
longer and made more of themselves to populate the expanses of ocean around
them.
It started to get a bit
crowded again, and not all could eat all the time, and this being a different
era than today, population control was a very natural phenomenon. They began to
compete. Some organisms did a poor job of gaining nutrients and died, not
bothering to pass on their genetic blueprints in a coherent manner. Some
organisms discovered they were advantaged and replicated incessantly. Some
organisms learned to attack and steal. Some learned to sense.
There was one Being in
particular. It developed a Spot.
This Spot was just a bit
of pigment to begin with, but this bacterium (because this Being was indeed a
bacterium), it realized this Spot could Sense. There were spaces in the world
that were bright and spaces in the world that were dark. It learned there were
spaces in the world that contained food and this food liked certain brightness,
or maybe it learned that its chloroplasts created more energy in places that
were bright. This special bacterium could not determine any more detail than
that, but seeing as how it didn’t know there was more detail to be discerned,
we can hardly expect it to be disappointed. It was, of course, thrilled, as I
feel any of us would be in such an unusual circumstance.
So while this bacterium
may have been the first, it certainly wasn’t the Only to develop a sensitive
photoreceptive Spot; numerous other Beings independently developed their own
Spots. More Beings followed and more Spots, too: some bigger, some more
complex, some with more cells, some with funny shapes. These Spots were partly
responsible for the first brain, too, as I think we could all agree that it’s
hardly rational to have a sensory-organizing mechanism before one has senses to
organize.
During an era, later
called the Cambrian Explosion, something incredible, but probably not
miraculous occurred. A slight structural development led to a huge grammatical
revolution and this Spot became an Eye; a Spot had curved in just a little. The
Being lucky enough to have such an Eye began to discern direction in light.
This was apparently useful because it became an extremely popular trend, very
quickly, and populations skyrocketed. Every Being wanted an Eye! Each
succeeding generation exaggerated the fashion a little farther, until
eventually, some Beings were sporting full-on depressions: whole Spots dipping
in like cups on the surface. They were proud of these developments. No one
could discern light directions like they could. They could move faster now,
with more assurance towards food and sunlight and possible mates (if they were
sexual of course… there was some discrimination even in these early times), and
with greater alertness away from the more competitive, or hungrier, types. They
could distinguish detail in their world with more clarity than anything ever
before.
Time continued to pass, as
it will, and the sensory cup deepened and deepened until it became a chamber,
forming an eye very much like the pinhole camera you might know of today. As
the size of the pinhole opening reduced, the Beings gained true imaging,
fine-tuning their directional sensing and even becoming capable of limited
shape-detection-- a useful tool. Every step forward meant more and more detail;
a greater understanding of one’s world; a greater ability to time one’s actions
to the sun or the moon for the best reproductive or energy or
resource-acquiring results.
The pinhole chamber was
rather delicate of course, being so complex and strangely shaped. The process
started by the little piece of stardust was not complete (and indeed continues
today in such a manner of development). Transparent cells grew like weeds
throughout the empty chamber space, preventing parasitic infestations and
contamination and ultraviolet radiation and anything else in the liquid world
that could get caught up in the ingress, while still allowing light to enter.
The fine cells of the chamber, then protected, began to specialize, fine-tuning
their refractive abilities to discern greater and greater details (even color!
what a whole, unbelievable new world). More pigments meant more colors, and these
eyes specialized in absorbing a narrow range of wavelengths-- the only two,
blue and green visible light, which could travel through the water of their
aquatic habitats. It was all the Beings really needed at the time. Some of
these specializing cells even granted the ability to maintain sight in or out
of the water… fast becoming a valuable tool as the Beings began to emerge onto
land! Cones and rods developed in response; distinctions between night- and day-vision
grew more important on these dry surfaces. Air was a less forgiving medium for
light than water.
These transparent cells
continued to be an invaluable development: the cells over the pinhole eye’s
aperture divided into two layers, separated by a clear liquid. This sandwich
effect thickened the eye cover to allow greater physical protection and the circulation
of oxygen, nutrients, wastes, and immune functions. The multiple liquid and
solid layers, naturally forming a biconvex structure, increased the Being’s
optical power, viewing angles, and image resolution. They felt empowered with
these high-powered lenses. But, maintaining these transparent layers of cells
was difficult and required too much energy for Vertebrate Beings. The eye
lenses began to be composed of specialized epithelial cells, saturated with
crystallin protein, and the nontransparent, living cellular machinery began to
be removed at the Being’s birth so it could see. This means, of course, that
the lens is dead cells, packed with crystallins, enough to last the Being’s
entire life. Relative crystallin concentrations, rather than its simple
presence, make the lens functional. Dead cells were easier to maintain, with no
need to supply nutrients or carry out wastes.
And still, it was not
enough! Sight made Beings more capable. Better sight made Beings more capable.
Independent transparent
and nontransparent layers split forward from the lens creating a separate cornea
and iris. This separation, like before, was also maintained by a circulatory
liquid in between, which additionally assists in refractive power. More blood
vessels and more circulation meant larger eyes and greater views (important, as
the Beings grew larger and stood taller). Larger eyes meant more optical
imperfections though, fortunately largely masked by the nontransparent ring
around the perimeter of the lens.
The greater development of
a Being’s central nervous system and brain proved to be rather important in
assisting this complex system. Photons absorbed by a chromophore, were
converted into electrical energy by a chemical reaction and then relayed to the
visual cortex. The brain would process this information and sends instructions
(if necessary) to the Being’s muscles (now so much more intricate than the
first Being’s smooth wiggles).
The structure of the eye
records its evolutionary history. The vertebrate Being’s eye, now located
within my own head, is built backwards and upside down, which necessitates the
passage of photons through a whole mess of substances -- the cornea, lens,
fluid, blood vessels, ganglion cells, amacrine cells, horizontal cells, and
bipolar cells -- before they reach the important light-sensitive rods and
cones, who can then send this information to my brain. This odd process allows
my outer retina to maintain a higher metabolic activity though, than the “right
way out” eye.
It is my opinion that all
creatures are imbued with a similar level of silliness. It’s entirely an
awesome wonder we, as full human beings, function at all, seeing as how we are
such an agglomeration of all this absurdity
My photoreceptive cell has
a long history and reflected within its pigments are the origins of the
universe. It seems even mundane tasks are ennobled by the knowledge that they
are being watched by the long-developed child of the stars.
