Exaptation for the good and the bad: regeneration and cancer

I discuss in this chapter the use of exaptation to create serendipity in an important biological process such as regeneration and in cancer. Regeneration is the capability to replace parts of the body lost after injury. As the immune system increases its complexity, this capacity decreases but, in the parts that are able to regenerate, we found a common signature between mammals and very distant organisms with high regenerative capacity such as Hydra, planaria and sea cucumber. On the other hand, tumour cells use the same genes related to Epithelial Mesenchymal Transition (EMT) to become more prone to migrate and to acquire an aggressive phenotype. Finally, I will discuss how the era of “Big Data” is helping us to identify processes that use exaptation to create serendipity.