Let me refute a growing belief in biology - that the cell theory is finished. “The cell concept is now an empty shell,” said a recent letter to Biologist, delightfully confusing metaphors, “. . . the cell, as the centre of structure and function, is dead.” I believe the opposite: that we can only understand ourselves as manifestations of the cells of which we are composed. Everything we do is a reflection of the separate cells whose choreographed interactions make us what we are.
In this era of molecular biology, the cell is viewed merely as a dynamic chemical system. Youngsters learn of DNA and enzymes, but see little of the intricacies of life. Life is predicated upon the cells which created the biosphere and regulate it still. The single cell is a temple of pluripotentiality. Cells can build wings with which to fly, scavenge for sticks to make homes, construct stone walls for protection, manufacture delicate glass globes of infinite intricacy, yet do not hesitate to sacrifice themselves wholesale for the good of the race.
Unlike humans, they can regulate their rate of reproduction to the available food supply, and many can create a hermetically sealed personalised ‘space capsule’ for long-term survival if their environment is disrupted. Of course cells are sentient. Some microbes can detect magnets or see where they are going.
We are seduced by the view that an amoeba is a simple creature, little more than a blob of plasm. In truth, its intricate life systems, undertaken by something so compact, connote complexity. An amoeba has a head and a tail (confine it in a cul-de-sac and it turns round to find its way out). With two sticks of firewood and an elastic band, anyone can show how a human walks. It is harder to model the ability of a water-soluble amoeboid cell to feed and reproduce, find (and approve) a sexual partner, sometimes even to unite in vast numbers forming a macroscopic body which heads off looking for a place to breed.
This is how we may marry those two opposing concepts of the zygote as an ultimate microdot, a seed for new life, and yet as the cell from which all later specialised cells can find expression. Multicellular organisms exist by potentiating specific functions in identifiable cell populations, whilst repressing those inappropriate to that site. Differentiation is the consequence the development, in a pluripotential cell, of only those features that are functionally appropriate.
This is no call for reductionism. I am not retreating to the cell, but starting with it and moving outwards to multicellular magnificence. The capacity of cells to build communities, like people, offers a truly holistic view of higher forms of life. By comprehending the cell, we can extrapolate from the model to embrace every multicellular species. In single cells we may model society. Every action of a many-celled organism is an expression of functions of those single cells. Lust and pair-bonding are mirrored when we see a grazing ciliate break off feeding to seek out, identify, and conjugate with a partner.
Homo sapiens is immortal. The single cells live on as the germ line: the ovum and the spermatozoon. There is nothing about the appearance of these cells to suggest that the two might fuse: that the globular cell might become infected by a swimming germ to initiate that process known as embryological development. We are the sporing phase on which the survival of these simple cells depends.
If you fix on the germ cells, then that is Homo sapiens, floating about in brine as microbial species did a thousand million and more years ago. We humans are moribund, no more than senescent fruiting-bodies facing an inevitable and distressing demise. People are the expendable husks which are supervened by the immortal germ cells. Such is the true nature of our kind. The cells matter, not us.
Microorganisms identify distinctions between self and non-self. Most fundamentally they do this when the time comes to select a mate, and when they display an ability to reject unsuitable partners. Cells have a finely tuned capacity to identify the non-self, and those of an immune system can extirpate non-self life forms with vigour. There are many areas in which antagonism of this sort - the animus of non-self rejection - exists within communities of living organisms.
Creatures have a remarkable ability to recognise their relatives. Bees can find their kin in the turmoil of a mixed community. Leaf-hoppers that are morphologically indistinguishable detect tiny differences in stridulation that mark one from another.
The culture of microorganisms offers the key to understanding the cultures of mankind. In recent years, in human medicine, much attention has been focussed on the study of auto-immune diseases, when the cells within the body start to attack other cells with whom they ought to co-exist. Lymphocytes are trained, as they mature in the thymus, to tolerate some external markers on cells, whilst rejecting others.
In countless nations across the world, disparate racial and cultural groups are mutually recognised and live supportively in the harmony of cooperation. We can model the conflicts in the news as an auto-immune disease - of society. It is one which training for tolerance can solve for people, as it does for cells.
Instinctual rejection of non-self may turn out to be one of the most fundamental properties of life; a unifying concept that stretches across biology. It is an area in which systemic theory and international relationships can meet, and where biology could offer an understanding of the origins of human conflict. By studying the ways of single cells we may at last perceive ourselves.
The cell theory is far from dead. I believe it is only just fit to come to life.