What is evo-devo?

First of all, it is about realizing a somewhat superficial similarity: that multicellular organisms, like trees, mushrooms and elephants, all started out as a single cell in two different ways. Each new elephant starts as a single, fertilized cell. This cell divides many times, and the daughter cells gradually become organised into different organs and tissues. This is embryonic development. But the elephant also has an evolutionary ancestor that was single-celled: before there were animals (or plants), there were only unicellular organisms. Even once multicellularity evolved, there were many ancestral species before we ever got to the elephant.

This means that the developmental program, the genetic code that generates an elephant, also evolved, generating all the ancestors before the elephant. All these ancestors also had to be viable organisms, so the evolutionary process could only involve changes that did not break the developmental program too badly. So while the evolutionary process created the developmental programs we see today, the continued evolution of development depends strongly on how the program currently works.

To see how development can have such a large effect on evolution, just consider how complex embryonic development really is. Between the instructions in the DNA, and the adult elephant, lie processes that playing out on spatial and temporal scales differing in several orders of magnitude. DNA encodes proteins, that interact and regulate each other to form the structures of cells; cells can change their behaviour and communicate with each other through chemical and mechanical signals; and many cells form tissues, that change shape and grow to form the organs of the embryo. All these levels of organisation also feed back on each other, adding even more layers of complexity. A consequence of all this complexity is that some mutations have a large effect on the phenotype, and some have no effect at all — thereby determining the variation available to evolution.

Still, evolution has in fact given rise to, and continues to shape, the developmental process. In fact, much of the developmental complexity is due to the millions of years of evolution having to work with “what is already there” — an engineer would have done things very differently. It is this feedback between development and evolution, and the consequences of this feedback that is studied in EvoDevo.

My research topics

coming soon