Some scientists describe a tumor as a caricature of normal development. In their view, a tumor can display unusual blends of tissues and forms. Take a teratoma as an example, where teeth and hair may appear in unexpected places. The appearance can be startling, almost like the tumor is on a quest, a biological search engine inside the body. It has earned the nickname a biological Google for the body because it seems to explore possibilities within its own tissues.
What is this search trying to uncover?
It probes different potential cellular paths that proteins could follow, mapping a vast landscape of possibilities. The body opens a field of opportunity through networks similar to digital dictionaries, encyclopedias, and other knowledge stores. In the tumor, however, the field of opportunity is physiological and cellular, governed by rules and constraints unique to this context.
Historian and philosopher Karl Popper spoke of a field of possibilities in his work, describing the universe as a growing domain where nonzero probabilities emerge over time. Building on that idea, the evolutionary view of tumors, sometimes called carcino-evo-devo, uses omics technologies—genomics, transcriptomics, proteomics, metabolomics—together with big data to define a biological possibilities space. This framework helps explain how tumors can pursue multiple trajectories at the molecular level.
Why would the body harbor such a search within tumors? The answer lies in evolution. The motive here is to increase the complexity of a multicellular organism. Complexity rises as simple units combine to form more intricate systems, a trend mirrored in chemistry where basic molecules like water give rise to complex macromolecules. Life itself emerged through chemical evolution, a concept central to modern biology.
One might wonder if evolution can proceed without simplification. The focus is on complexity, not merely reducing things to basics. How does this amplification of complexity occur? After the genetic code arose, the expansion of biological complexity was steered by genome evolution. New structures can be planned in advance, encoded in DNA even before their physical form exists. In other words, information about future structures can be prepared at the DNA level, guiding development ahead of the moment when those structures appear.
Consider the immunoglobulin locus in mammals. This locus is a sophisticated mechanism that generates a vast diversity of antibodies to recognize foreign antigens. Immunoglobulins are antibodies, and the loci that encode them act like a recombination engine, capable of producing a wide range of antibody variants. Some describe this system as a biological computer because it computes and adapts in real time to unknown threats.
Does the biological computer operate specifically within tumors? In many ways, yes. Tumors act as an opportunity space where new gene combinations and tissue variants can emerge. Is that space truly vast? A rough estimate suggests a near tenfold to elevenfold diversity in antibody options alone, and the vertebrate genome supports a broad array of morphological features and cell types. If the immunoglobulin locus can calculate antibody diversity, the broader genome could, in principle, compute the full spectrum of vertebrate morphology. This view frames the tumor as a testing ground for evolutionary potential at the cellular level.
What about the human organism as a whole? Tumors may appear frequently, yet the immune system often keeps them in check. In mammals, up to about 80 percent of tumors are benign, and the reasons for their emergence can remain unclear. The theory presented here offers explanations: options within a tumor may be explored, and some choices prove useful in an evolutionary sense, even though tumors are pathological from a human health perspective. This process can lead to the formation of new cell masses, the emergence of novel cell types, tissues, and eventually more complex organisms.
How are new cell masses inherited? Inheritance can involve hereditary tumors, a surprisingly high proportion compared with classic genetic diseases. The explanation is straightforward: these traits are passed down in the same way as many cell types, arising in germline cells rather than somatic ones. Therefore, they are inherited through the germline. Evolutionary new genes do not originate in somatic tissues; they arise in germ lineages and are transmitted to offspring.
Does the concept of a biological computer hold up as a general principle? The answer is affirmative. It is observed that the body recalculates responses to new pathogens by adapting to ever-changing conditions. Early theoretical work, including a paper published in a prominent biology journal in 1979, explored how selection proceeds along compatible features. Compatibility drives the growth of complexity, as new genes appear and molecular networks become more elaborate. The tumor, in turn, seeks compatible configurations within the field of biological possibilities, driving innovation while remaining bounded by prior structure and function. When signs clash with previous patterns, the outcome can be detrimental and may lead to organismal failure, underscoring why malignancy can arise when compatibility falters.
Are malignant tumors simply a failure to find compatibility? They can be. The question of new organ development in humans has even touched the edges of contemporary biology. For instance, a tissue discovered around 2015 in the spinal canal of a person was identified as ependymal tissue overgrowing the central canal. This discovery highlighted that tumor-like growths can occur in unexpected places and contribute to ongoing evolutionary change. The broader insight is that evolution can generate novel gene activity and tissue arrangements that are not yet fully understood, including tumor-specific expressed, evolutionarily new genes.
What organs might be regarded as relatively new in the human body? Among those discussed are the placenta, mammary gland, prostate, and adipose tissue—areas that sometimes exhibit tumor-like dynamics. This observation suggests that tumors may reflect ongoing refinement of these structures by evolution, a topic that invites further discussion and study about how tumor dynamics intersect with normal organ development.