That’s you and me at our first moment of existence.
By Randall K. O’Bannon, Ph.D. NRL Director of Education & Research
When the cell was first discovered (and named) by Robert Hooke in 1665, it was hailed as a major discovery. However it was initially thought to be just a cell wall containing a mass of some sort of undifferentiated protoplasm.
It took years for scientists to learn just how complex that “simple cell” really was.
Gradually, they realized that even the standard animal cell contained many different highly specialized organelles–structures that perform various jobs inside cells. For example, these complex biological machines keep the cell healthy and thriving by handling critical manufacturing, processing, transportation, and communication functions for the cell. Even the cell wall turned out to be a very specialized structure. It admits or blocks the entry or exit of materials or molecular messages meeting very specific conditions, ready to perform very specific functions.
The nucleus was easy to pick out, but its full significance has still only recently begun to be appreciated. The nucleus is, of course, the “command center” which controls and regulates the cell’s activities. However, it is the also the storehouse for the cell’s DNA (short for deoxyribonucleic acid) which contains the unique blueprint for the fully developed animal—however many trillions of cells that may be, however many dozens of unique types of cells are needed to make up that organism.
The profundity of this cannot be overstated. Within that single cell, in that DNA, are the full set of instructions for building a fully functioning adult organism with all its complex working parts and organs. It is as if a single microscopic dot contained not just the blueprint for a large skyscraper, but for a city full of skyscrapers, with plans for all the roads, the vehicles, the farms and the grocery stores, the water and sewer systems, the hospitals, law enforcement, power production, the communications system, the factories and more. And of course, with a great deal more complexity and efficiency than can be found in any modern city today.
Have a look at the human heart.
Take the specialized master pump of the circulatory system, the four chambered human heart. Here we have three layers of cardiac muscle, carefully calibrated to operate in a steady but flexible rhythm. The beating of that heart assures that every cell in the body gets the oxygen and nutrition and healing factors it needs, all the while making sure that waste is carried off and depleted corpuscles are replenished.
Each function, each element of the system has been carefully orchestrated by the code of that first single cell.
The same with the lungs, the other side of the cardiopulmonary system. With the help of the diaphragm and the tiny capillaries of the alveoli, lungs are capable of extracting oxygen from the air and delivering it to the blood stream while also removing carbon dioxide from some of those same cells and releasing it back into the environment.
Consider the human hand.
Within that single original cell (called the human zygote), there are codes for building each of the twenty-seven specialized bones of the hand, giving structure and flexibility to the wrist, palm, and fingers. These bones are growing, living material, containing marrow generating stem cells that give us red and white blood cells.
Blood vessels strategically placed throughout the hand form a system of arteries, veins and capillaries that carry nutrition to every type of cell and tissue found there, providing energy and oxygen for them to grow and function. Those blood vessels also carry away waste products and deoxygenated blood to be purged and renewed.
Also in that very first cell’s instructions are the elaborate system of muscles, ligaments, tendons and sheaths that give the hand the strength and ability to grasp, hold, move and manipulate various elements and objects of a great variety of sizes, shapes, and weights.
An intricate system of sensory nerves allows the hand and fingers to detect changes in temperature, pressure, even the slightest variation in surface texture or shape. Highly specialized motor nerves enable bones and muscles to work together, performing intricate and complex movements, offering great agility and strength as well as the capacity to make fine, nearly instantaneous adjustments to constantly changing circumstances.
Several layers of skin offer both covering and protection for bones, muscles, nerves and blood vessels, in addition to playing critical roles in regulating body temperature, water and electrolyte balance, and the synthesis of vitamin D. Owing to high concentration of sensory nerves, the skin of the palm and fingers are especially sensitive to pleasant and painful stimuli. The connection of those nerves with the ridges of the fingertips make them particularly good at gripping, holding, and managing fine calibrations.
Each and every layer from bone to muscle to nerve to vein to skin is all extremely specialized and connected and coordinated. That same hand has the ability to
… tie a shoelace,
… build a house,
… plant a tree,
… assemble a circuit board,
… write on a chalkboard, read Braille, use sign language, text a friend,
… steer a race car, hit a baseball, throw a football, shoot a basketball, swing a tennis racket,
… give your spouse a helping hand or a massage,
… build a sandwich or prepare a gourmet meal,
… sew a shirt or chisel a statue,
… play ‘Chopsticks” or a Chopin sonata,
… type a college paper or a bestselling novel,
… perform a card trick or do brain surgery,
… finger paint or paint a Mona Lisa,
… hold the hand of a young child or mop the brow of an aged parent.
The capacity to do all these things is contained in that single tiny special cell, in the zygotic human being. And this is just about the marvel that is the human hand!
There are yet many more marvels to consider.
Even before getting into the marvelous mystery of the human brain, consider the unique sensory capacities found centered around the human face and head. Within the instructions encoded in that single celled human zygote are all the specialized cells, structures, sensitivities, systems and neural networks necessary for a human being to experience a glorious variety of inputs from the environment in the form of smells, tastes, sounds and sights.
If you doubt the complexity involved there, just open the back of your computer or TV or sound system and try to explain how every module and circuit function to be able to give you just a facsimile of the reality your eyes and ears deliver you daily. And though your favorite cooking show may present something so compelling it makes you salivate, to actually smell or taste it, you’ll have to bring in a couple of entirely new sensory systems science is still working to understand and artificially replicate.
And what about that brain, with its hundred billion or so neurons and synapses, storing facts and memories, providing a seat for consciousness, processing logic and mathematics, managing the body’s physical systems, recognizing and responding to the environment, considering a course and initiating the body’s actions?
Yes, once again, every bit of that is all set up according to the precise instructions found in that original single human cell formed at conception – the zygote.
There is nothing like that single cell in all of nature.
The zygotes of other animals may contain genetic blueprints for some amazing creatures, but none possess the full set of capabilities and capacities of humanity. Other human cells contain human DNA, but do not exist in the conditions that fully activate that genome and cause the division and differentiation that gives rise to all those various interconnected, coordinated and specialized parts and systems.
It isn’t just that these are elaborate plans or blueprints amazingly shrunk and stuffed in a tiny package, some novel microscopic library. They are living cells, human beings who are alive, growing, interacting with their environment, actively moving on to their next stage of development and engagement.
Even more amazing, with all that elaborate precision and complex detail contained in that cell, there is still room for great individual variation so that no two human beings are ever precisely alike. So every human being is remarkable and every human being is remarkably unique!
This too is part of that single, first human cell. What we have here isn’t just that first instance of humanity, but the first appearance of a particular, unique individual human being.
That’s you, at your first moment of existence. That’s me. That’s every single one of us exactly as we were at that first amazing initial stage of our lives.
So, is the single celled human zygote just another cell, just a tiny, insignificant mass of protoplasm?
Sure, if the Ceiling of the Sistine Chapel by Michelangelo is “just a painting.”
1. As with any major scientific discovery, there are many disputes over who first saw what and who it was that first understood what he or she was seeing, but it is widely agreed that Hooke was the one who first named the cell, likening the chambers he saw in the slice of cork he was observing in a microscope to the cells where monks lived in a monastery.
2. There are an estimated 37.2 trillion in the human body, according to the Annals of Human Biology, Nov-Dec 2013. The American Association for the Advancement of Science says there are over 200 different types of cells found in the human body (“The Cells in Your Body,” accessed 9/14/21).
3. Twins, while sharing the same original DNA, always display at least some small difference, perhaps due to environmental or epigenetic factors experienced during development, so that those who know them well can tell them apart.