Contents

Epigenetic Tracking is a biological model, originally conceived as a model of embryonic development. Computer simulations proved the capacity of the model to generate complex 3-dimensional cellular structures, and the potential to reproduce the complexity typical of living beings. The most distinctive feature of this model is the presence of a homoge-neous distribution of stem cells, which are continuously and dinamically created during development from non-stem cells and reside in niches. Embryonic stem cells orchestrate early developmental events, adult stem cells direct late developmental and regeneration events, ageing stem cells cause ageing and cancer stem cells are responsible for cancer growth. The conceptual backbone provided by Epigenetic Tracking brings together a wide range of biological phenomena: for this reason, we think it can be proposed as a general model for multicellular biology. Despite, or perhaps due to its theoretical origin, the model allowed us to make predictions relevant to very diverse fields of biology, such as trans-posable elements, and cancer-related patterns of gene mutations. This paper contains a comprehensive review of the model and its implications. 1 a