Coast Chronicles: Blessed bodies and our inner beasts

<I>Nobu Tamura illustration/Wikipedia Commons</I><BR>The Tiktaalik is not just any freshwater fish. This fossil fish from 375 millions years ago, dug up from a shelf of frozen rock on Ellesmere Island in the Arctic, provided explicit evidence that it was the first fish to crawl up onto land.

Gary Snyder has a collection of poems called "Real Work" and the phrase "chop wood, carry water" comes to mind.

Springtime is about sap flowing, leaves opening and physical labor again at center stage - house cleaning, tilling and planting the garden, mowing, sorting and taking unused items to consignment shops or the dump.

Our bodies, after a long winter slumber, are (we hope) charged up and ready to walk, run or shimmy through another cycle of the seasons.

Cycles This past weekend, Paul and Crystal Springer arrived from Vancouver to mow Alice and Winston's sprawling lawn after their deaths six days apart a couple weeks ago. I know wherever Winston is he's cussing because no one has planted the garden he tilled the last time he was home.

Then I met my next door neighbors, Chris and Bonnie, out doing yard work too.

"Yes, our folks just can't make it to the beach anymore," said Bonnie. "They're in Vancouver so Chris and I came up when we thought we'd have a couple days of good weather. Chris is on the roof."

"But the molehills! I stopped counting at 150," she said before returning to weeding.

These amazing bodies - their muscles and joints, each toe, the phenomenal opposable thumb, soft tissue organs, the synaptic brain - this community of flesh we're in charge of is a perambulating miracle, a workhorse of design.

And we owe it all to 4.5 billion years of evolution.

Fishibians As Neil Shubin tells us in "Your Inner Fish" (Vintage Books, 2009), we are - depending on your view - either an amazing compilation of successes layered one over the other; or a complex system of jury-rigged evolutionary adaptations. Or probably both.

I took a deep dive into his book from the first moment I spotted it on the University of Washington bookstore stacks. It is spectacularly mind-blowing, especially for us non-science types.

Shubin is a paleontologist and professor of anatomy with a specialty in fossils.

You may remember that I wrote about the development of the human hand some weeks ago and one of the features was Shubin's discovery of Tiktaalik, which means in Inuktituk, "large freshwater fish."

Tiktaalik is not just any freshwater fish however. This fossil fish from 375 millions years ago that Shubin and his team dug up from a shelf of frozen rock on Ellesmere Island in the Arctic provided explicit evidence that it is the first fish to crawl up onto land.

Tiktaalik has both a wrist - jointed for walking or at least pushing itself upward, something a fish has no need for - and a neck bone array - which means it can lift its head up separate from its spine.

Tiktaalik is, in fact, one of our ancient ancestors and one in a sequence of evolutionary fish-forms called "Fishibian."

Fishibians represent perhaps the most complete fossil record of a set of transitional evolutionary steps by which fish crawled out of the water an onto land. This transition happened during the Devonian period of earth's history - starting between 385 and 380 million years ago, give or take a few.

Let's run through these just for fun, in order: there's the Eusthenopteron; Panderichthys; Elginerpeton; Ventastega; Mextaxyganthus; Tiktaallik; Acanthostega; and, last and actually least, Icthyostega. (That should give our proofing team hysterics.)

These creatures have both fish-like and amphibian characteristics, hence, fishibians.

The Origin of Spines Let's take the last one in line, which was actually the first one discovered, in 1932; but as you might guess, it baffled scientists. Icthyostega has four limbs and a skull (amphibian) but also the definitively fishy lateral line sensory organ that tells a fish about water pressure and currents as it swims.

You can visually see this line running down both sides on any fish body.

Just as a tiny aside in the huge story called Planet Earth, this lateral-line sensory system became our spinal cord.

And if we dig back deeper in time to search out its origins, Shubin tells us that one of the first appearances of the spinal cord existed inside a little worm called Amphioxus.

"Amphioxus is a worm, an invertebrate, that shares many features with back-boned animals such as fish, and amphibians, and mammals [us]. Amphioxus lacks a backbone, but like all creatures with backbones, it has a nerve cord that runs along its back."

"In addition, a rod runs the length of its body, parallel to the nerve cord. This rod, known as the notocord, is filled with a jelly like substance and provides support for the body."

"As embryos, we have a notocord too, but unlike Amphioxus's, ours breaks up and ultimately becomes part of the disks that lie between our vertebrae" (Shubin, page 94).

An even older ancestor of the Amphioxus is a worm that lived 530 million years ago, the Haikouella. Three hundred individual fossil specimens of this worm have been found in southern China, and they too have a rudimentary notocord.

Evolution and Deep Time You see what I mean about mind-blowing? First of all, who can even understand what 530 million years means? And then, some little worm invented the precursor of the spinal cord that we know and hold dear. Right!

I know that the Long Beach Church of the Nazarene has had on their reader board for a couple weeks this note: "Gods [sic] animals defy evolution."

I say God's animals edify evolution.

I mean, look, who created the fish's lateral line sensory organ? Wait, we have to go back to Amphioxus's notocord. No, even further back please to the 300 or so versions of Haikouellas who invented it - one or two or 50 of which passed on this evolutionary trait to other creatures that eventually passed it on to us.

But did life invent itself?

Evolution does not preclude a higher power. It clearly illustrates a design working over vast stretches of time in ways that follow certain biological rules of survival.

Let's look at another of the critical body parts that we can thank fish and amphibians for - the bones of our middle and inner ears.

At between 23 and 28 days of development, the human embryo, which has looked until then like a folded tube, has a blob on one end that will become a head. Four little swellings start forming on this blob end: at three weeks the first two form, and in four more days the last two form.

Our Inner Ears These are called "arches" and every fish, amphibian or mammal embryo looks similar at this point - they all have four arches.

These arches have a mix of cells that will become various parts of our heads.

The first arch tissues form our upper and lower jaws, two tiny middle ear bones and all the vessels and muscles that supply them.

Arch two forms the third small ear bone (the stapes), a tiny throat bone, and most of the muscles that control facial expression.

The third arch forms bones, muscles and nerves that we will use for swallowing further down in our throats. And the fourth arch forms our larynx, its muscles and vessels.

Through DNA and fossil study, scientists can trace bones from these so called "gill arches" to our ears, first during the transition from fish to amphibians (their hyomandibula bone becomes our stapes) and later during the shift from reptile to mammal, the reptilian jawbones become our hammer (malleus) and anvil (incus).

Nature does not throw anything away unless it is absolutely unusable, most inventions are repurposed or recycled. These bones in fish are migrated into use to create our exquisite hearing apparatus suitable for sounds projected in the air rather than the water.

Blessed Bodies But what I really wanted to talk about were these bodies - I mean simply the concept of a body. Where did it come from?

For millions of years there were no bodies, there were only single-celled organisms floating around in a rich soupy world of water.

How did we get a front and a back, a head and a tail?

For that, dear readers, we'll have to wait one more week. Or pick up your own copy of "Your Inner Fish" - it will make your tail spin.

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