It is evident that existing biological theories, heavily influenced by evolutionary thinking, have largely neglected causal relationships between genes and cells, as well as between cells and the physical body. They have failed to explain in detail how the disordered elemental materials of nature gradually become organized to eventually form the physical body of a species. This issue encompasses the origin of species as well as their survival and reproduction post-origin, including issues most closely tied to humanity-birth, aging, illness, and death.

To properly address these issues, it is necessary to explore and research the relationship between the origin of species, the self-regulatory laws governing species post-origin, and medicine, as well as the inherent laws embedded within each theory. That is exactly what this body of work does.

After the publication of Revisiting the Origin of Species by author Thierry Hoquet, readers raised many questions, reflecting the persistent reliance, whether conscious or unconscious, on evolutionary thinking in their consideration of species origin. To articulate the new perspective on species origin more concretely and provide a more detailed and holistic understanding of species' physiological processes, Zhang conceived the idea of On Species, which bridges species origin and medicine.

The essence of On Species is a synthesis of holistic biology and holistic physiology. It investigates the formation of the physical body of species and the many factors involved in this process, elucidating how inorganic matter transitions into organic matter and ultimately into the form of life. It examines the relationship between stability and freedom at various structural levels of the species' body, positing that any species can only vary within a limited range at both genetic and physical levels.