Biology has had a hell of a revelation since Linneus started the characterization of life. The system of taxonomy, such things as a taxon, are incredibly useful to the study of the first-year medical student learning the Form of the Human in Wellness. How does one decide similarities and differences? When one documents, one should ideally be able to point out the variances from normal, not a recitation of all the things observable, which is a waste of time. One needs to learn the principles of conceptual clustering; how one goes about the sorting of things. Such things are poorly studied by undergraduates.
The miracle of Mendel’s discovery is that many of the elements of form studied by Linneus are linked to single, individual and morphologically important genes. Phenotypes are driven by genotypes. This is far from being understood. We know of genes as producers of chemicals, enzymes, THINGS. We know far less about how genes make form.
D’Arcy Thompson studied the growth of organism in “Of Growth And Form.” He used mathematical principles to organize the representation of phenotypes (e.g. see picture.)
Thompson’s thoughts are very descriptive. They do not offer a unifying thesis between form and gene; there is not really one to this day. All we know is that some of the major physical operations on form that produce the classification of the various elements of Linnean classification are related to genes. How they present in hierarchy is one of the challenges of the 21st century.
They helped reinforce a materialistic approach to biology, especially human biology. Think of it. We know that there is a relationship between single gene and form. People who do not develop the central ray of the hand during embryonic development have ectrodactyly, or “lobster-claw” hands. It comes from a single gene, and is heritable. See a person with claw-hand discussing ectrodactyly on YouTube.
It could be conceived that phenotype would be a summary of many formation genes, rather than one, or a few, stubbornly persistent phenotypic genes.
As I’ll discuss later, This finding, in its time, led to a concept of divisibility and materialism in human biology; a concept that biased modern medical science to this day.