22. A Poem Written in Hydroxyapatite: How a Little Bone Revealed a Hidden World

poem = something that arouses strong emotions because of its beauty

The poem of which I now speak is an ode that can be held in the hand. Found on the forest floor, which I had been intently scanning for morels, it was a prize. Granted, a morel is most certainly a gift as well. But this treasure was something much more. Though unpalatable, it was a delicious reminder of the wondrous, labyrinthine complexity of our natural world. Thirty-five millimeters in length, 20 millimeters in height, 15 millimeters in width, and a ghostly white in color was this piece of inorganic poetry. It was the phalangeal bone of a white-tailed deer, a toe bone. How it came to be there all alone on that square foot of woodland floor was a puzzle. How it had achieved its perfection of form presented me an even greater mystery.

As I examined the bone now lying in my hand, it seemed perfectly sculpted as if by the complex software of a 3-D printer. The proximal surface of the bone was marked by two deep, exceedingly smooth-surfaced concavities. Anatomists call these fossae. In this case, they were surfaces made to articulate with the phalangeal bone which once rested above it in the deer’s foot. The distal end of the bone bore two knuckle-like ridges. Condyles these are called. They would have adjoined the toe bone overlain by one of the deer’s hooves. I was willing to bet that each ridge, fossa, and curve of the bone I held would be virtually identical to the middle phalangeal bone of any other white-tailed deer. How this uniformity, this perfection of shape, this faithful commitment to structural design?

The simple answer, of course, is that the instructions for making the middle toe bone of a white-tailed deer are encoded in the deer’s DNA. Comparing these instructions to computer software likely does an injustice to the astounding functional complexity of the genetic code. Having taught biology for many years, the central dogma of DNA structure and function I understand. I grasp the concepts of DNA replication, transcription, and translation. I can explain and diagram the basics of what is entailed in transforming genetic code to protein should anyone be inclined to ask. But then I find myself chancing upon an object such as this, some phenomenon from the world of living things, and I find myself adrift.
So it is with the diminutive toe bone lying in my hand. It does indeed arouse strong emotions of wonder. How can a series of organic compounds – the A’s, T’s, G’s, and C’s of DNA – result in such perfection of form? How do the bone forming cells of the tiny, fetal deer know how to lay down this hydroxyapatite matrix? How do these cells know how to fill this template with fibers of protein, lengths of neuron, tunnels of lifeblood? By what molecular instinct are its ends sheathed with cartilage? How did this tiny bone know that it had reached its exact proportions of length, width, and height and that it was time to stop its growth? Yes, of course I know the blueprint is encoded in the deer’s DNA. But I still marvel at the plethora of tiny details that must occur at the microscopic, cellular level of growth and development. How are length, form, and composition being transferred between cells and raw materials? How is the exact placement of osteoblast, chondrocyte, and osteoclast communicated? All these questions arise from this one tiny bone. And consider the plethora of other bones in the deer skeleton. Each has been laid down with the uniformity of structure precise to Odocoileus virginianus. All have their myriad articulations, facets, bodies, processes, and passageways for blood vessels and nerves. Sinew and hide, aorta and antler, hoof and heart are all constructed to precise specifications with an accuracy that seldom fails. The detailed instructions for all these are written by means of a modest four-letter alphabet – A (adenine), T (thymine), C (cytosine), and G (guanine); so simple to recite, so astounding to contemplate. Limitless questions, countless considerations course through my mind as I run my fingers gently over the little bone.

Even among the ancients the miraculous, enigmatic wonder of life itself was recognized. We are “fearfully and wonderfully made” the Psalms proclaim. It requires only a tiny leap of reasoning to understand that this reference to the phenomenon which is the human species extends far beyond our selves. Today we better appreciate that the astoundingly intricate nature of life applies to every organism on our earth. All are “wonderfully made.” We now more fully understand that this miracle is spawned through the interplay of superbly complex biological mechanisms. Be it ant or ash, worm or warbler, millipede or me, the organic world expresses itself through genetic, cellular, and physiological contrivances which should leave us in awed reverence.

These biological processes are coded for and directed by DNA, an immortal thread that stretches back to the beginnings of life on earth. It is a self-replicating compound of extraordinary control, amazing elasticity, and astonishing potential. It is the shared strand that has been passed from generation to generation up through the branches of the biosphere’s phylogenetic tree. In this way, DNA weaves all life into the quilt we call biodiversity. Our small, blue world is such an extraordinarily special place – so beautiful, so enriched by its distinctive life forms, so unique within the cosmos.

The little phalanx now resides upon my desk. Periodically, I find myself requiring a gentle reminder that I live in a universe of immense wonder. To satisfy this want, all I need do is glance upon this elegant poem written in the language of bone.


photo credits:
     bone specimen by the author
     DNA by Richard Wheeler at Wikimedia Commons
     geologic time spiral by USGS at Wikimedia Commons
     earth rise above the moon by Goddard Space Flight Center. Ariz.     St. Univ.