From embryology, we know that our bodies are organized around three basic cell types: Endoderm, Mesoderm, and Ectoderm. As we grow these cell types attempt to maintain genetically defined ratios to each other. However, these ratios are an approximation and in almost everyone, there is a relative dominance or deficit of one or two of these three cell types. This “imbalance” can be observed in the appearance of the physiology of an individual1.
The emergence of these cell types follows our evolutionary trajectory. The specialized adaptations animals acquired required specialized cell functions. For example, movement requires muscle and skeletal cells (Mesoderm). Movement relies on sense organs and some form of cognition to decide where and when to move (Ectoderm), and all living things need to process, assimilate nutrients to grow and reproduce (Endoderm). It is possible to recognize the relative dominance of these three tissue types in any individual. This activity was called Somatotyping by William H. Sheldon.
Somatotyping can be linked to the Dimensional Mastery Model, offering visual cues as to which evolutionary paradigm is most dominant and hinting at which therapeutic strategies cataloged in the model would have greater efficacy. It is likely that somatotyping is done either consciously or unconsciously by all effective therapists.
The foundational cell type in our bodies is Endoderm which forms our viscera and organs. This can be thought of as the cell type which shares a common ancestor with all organisms. It is this tissue type that handles the basic processes of life.
Endomorphs are generally more social, more able to simply be present at the moment. Their emotional reactivity trends to grief.
Movement required the emergence of a cell type to handle this specialized task. Mesoderm is the tissue type of our muscles and skeleton, which we share in some variation with all organisms which move.
Mesomorphs are more action-oriented, often taking the role of a leader in getting things done. Their experience of time is more linear, comfortable stepping through a plan to achieve a goal. Their emotional reactivity trends towards anger.
In this model Mesoderm is the tissue type associated with Vertebrates
While animals were figuring out the how of movement, they also needed to figure out the where and why. This required the development of complex sensory systems, and the ability to think through the relevance of what they were sensing. Ectoderm is the tissue type of our nervous system. It is common for Ectomorphs to state that they feel as if their nervous system is right on their skin, and their emotional reactivity trends towards anxiety.
The pictures shown above illustrate quite pure forms of tissue type dominance, which are quite rare. We almost always fall into a blend somewhere in the middle of these three types, making assessment somewhat more challenging. These charts illustrate for men and women where we tend to cluster. (Click on the chart for a full-screen pdf)
1: “Atlas of Men, A Guide and Handbook on Somatotyping” William H. Sheldon 1954