WHAT DOES IT MEAN TO SAY WE ARE COMPOSED OF CELLS?
Until the 1660s the smallest object human eyes could see was a mustard seed or speck of dust. That changed when Robert Hooke devised a microscope and described the structure of cork bark as made of a myriad of what he called cells. He had no concept that life was composed of cells; that came later, when German scientists in 1838 described plants and animals as communities of cells. By the 1860s a new field of microscopic anatomy (called histology) studied tissues and related them to function as well as to disease. With this knowledge came Rudolph Virchow’s cell doctrine. Every individual’s life has its origin in a single cell.
When we contemplate that the one cell that gave rise to our present self has now produced 100 trillion cells in an adult body, that is a staggering realization of the multitudes of cells we contain. Scientists quickly learned that the tissues were related to function. Some cells are contractile like muscle. Some secrete digestive juices like those that line the insides of our guts. Some are sacs of hemoglobin, like our blood cells. This tells us that our body is a community of specialized regions carrying out different functions. It also tells us that because we are unaware of our cells unless we see them under microscopes, we tend to ignore them. This makes us vulnerable to agents that alter cells (usually the genes they contain) and result in tumor cell formation. We are also vulnerable to agents that alter reproductive cells and produce birth defects if not in our children then in some future generation that gets the damaged gene causing a birth defect. Because our education for the past two or three generations has largely minimized the ways our cells can be damaged, we are not likely to protect ourselves adequately from harm. That will change as science penetrates our education and our culture more forcefully in the coming generations. It took a half-century or more before the germ theory penetrated public consciousness and made us aware that there are germs that can cause illness or death. Yet there are still those who believe infectious diseases are imaginary and that all illness arises from loss of faith or is meted out by a fate beyond human understanding.
But there is also a pleasurable side to knowing we are composed of cells. It enriches our knowledge of life and how it works. It stimulates our curiosity to know how cells change in composition to acquire different functions as we shift from being a fertilized egg to an embryo, fetus, child, and adult. It may challenge our sense of who we are when we consider that it is possible to take adult cells, shift them into an embryonic state, and produce a clone or individual who is an identical twin of the individual who contributed that cell. Twins who are a generation apart may not be the same in personality and interests as twins raised together from birth. Right now that cloning is done in dogs, sheep, or other mammals but it is very possible that someone will do this for humans. In our more morbid science fiction imaginations we can imagine a world-controller who produces a nation cloned of himself and perhaps his wife and arranges the sterilization or death of all others. It freaks us out, but it is not likely to happen, any more than having Congress and a President ordering the sterilization of all Americans who cannot trace their ancestry to the Revolutionary War.