Molecular and Systemic Epigenetic Inheritance: Integrating Development, Genetics, and Evolution

Currently, a central problem for theoretical biology is the integration of development with genetics and evolutionary theory. Through the late 20th century, biologists held that animals resemble their ancestors strictly because of the transgenerational transmission of DNA. This view effectively wrote development out of evolutionary biology. However, many molecular and developmental biologists now understand that phenotypes-anatomical, physiological, and behavioral traits-are not determined by genes (i.e., DNA segments) alone; instead, they emerge epigenetically from developmental processes involving co-acting genetic factors, environmental factors, molecular epigenetic factors, and other non-genetic factors within organisms' bodies. This insight forces a rethinking of biological inheritance. Perspectives focusing on the dynamics of developmental systems offer a compelling alternative way to think about inheritance, providing a powerful substitute to the reductionistic framework that attributes phenotypic outcomes to genetic instructions set in advance of developmental processes. Rethinking genetics, epigenetics, and inheritance by focusing on the dynamics of developmental systems helps highlight the bidirectional effects of evolutionary and developmental processes on one another, yielding a more integrated understanding of development, inheritance, and evolution. Simultaneously, this approach encourages rejection of genetic determinism, a simplistic perspective that continues to appear in psychological writing, despite its biological implausibility.