Abstract
The role of embryology in metazoan evolution is rooted deeply in the history of science. Viewing Neoplasia as an evolutionary engine provides a scientific basis for reexamining the disease cancer. Once the embryo is understood as a benign tumor with a pivotal role in the evolution of all animal forms, there will be an immediate paradigm shift in the search for cancer cure, potentially revealing insights that may be buried within the great developmental transitions of metazoans. This article discusses one of the unifying principles between embryology and oncology, namely cancer stem cells. Some considerations are also provided on the central role of physics and biomechanics in the assembly of the first embryo, which can be regarded as a differentiated benign tumor. Mechanical impregnation of the nucleus of a stem cell, culminating in a totipotent/multipotent cell, was a major event safeguarding the success of embryogenesis throughout evolution. Germ cells in the earliest ctenophore embryos underwent delayed differentiation, subsequent to the mechanical assembly of the embryo. Finally, a discussion is presented on the concept that cancer and embryogenesis (cancer and healthy stem cells) are two sides of the same coin, that is, of the same process. The only difference is that cancer stem cells reveal themselves in inappropriate contexts. Neoplasia is a free force, whereas cancer is a force contained by animal organization.