There is more to heredity than genes: some acquired information is inherited and evolutionary change can result from instruction as well as selection. Molecular biology has demonstrated that many of the old assumptions about the genetic system are incorrect. We now know that cells can transmit information to daughter cells through non-DNA (epigenetic) inheritance. This suggests that all organisms have at least two systems of heredity. In addition, many mammals transmit information behaviorally, which grants them a third heredity system. And humans possess a fourth system: symbol-based inheritance, particularly language, which plays a significant role in our evolution. It is therefore incorrect to think of heredity and evolution only in terms of classical genetic systems. Epigenetic, behavioral and symbolic inheritance systems all provide variation on which natural selection processes can work.

Eva Jablonka and Marion Lamb (2005) have detailed the many different forms of epigenetic inheritance systems-EISs (see their Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life published by MIT Press). Jablonka and Lamb described the following EISs: self-sustaining feedback loops-memories of gene activity; cellular structural inheritance-architectural memories, e.g., prions in Creutzfeldt-Jakob disease, i.e., ‘mad cow’s disease’; chromatin-marking systems-chromosomal memories (chromatin is the DNA plus RNA, proteins, including histones, etc.-the ‘stuff’ of chromosomes)-methylated DNA significantly influences gene transcription and is also a part of the heredity system that transfers epigenetic information from mother cells to daughter cells; and RNA interference (RNAi) which leads to the stable and cell heritable silencing of specific genes (depending on small RNA molecules known as siRNAs). Besides the pathways of genetic and epigenetic inheritance, Jablonka and Lamb (2005) delineate two more inheritance systems: behavioral and symbolic, the latter two being significant for psychosocial scientists in their attempts to understand mental illnesses.

Epigenetic research, I firmly believe, will become much more significant in the future as applied to psychiatric disorders. The pharmaceutical companies are already researching how their psychopharmacological agents impact on the epigenetics of psychiatric illnesses. However, since the role of the social environment looms much larger within psychiatric epigenetics, psychosocial interventions, including most importantly, psychotherapy, will be increasingly recognized as potentially ameliorative.

Brian Koehler PhD
Postdoctoral Faculty
New York University
80 East 11th Street #339
New York NY 10003
212.533.5687
brian_koehler@psychoanalysis.net