Embryologists at University College London have helped solve an evolutionary riddle that has been puzzling scientists for over a century. They have identified a key mechanism in the initial stages of an embryo's development that helps differentiate more highly evolved species, including humans, from less evolved species, such as fish.
Early on in development, the mass of undifferentiated cells that make up the embryo must take the first steps in deciding how to arrange themselves into component parts to eventually go on to form a fully developed body. This is a process known as 'gastrulation'.
During this stage, the cells group into three layers, the first is the 'ectoderm' which then in turn generates the 'mesoderm' and 'endoderm' layers.