Abstract

While one can hardly express enough the immense contribution of Charles Darwin’s “On the Origin of Species” to the foundation of modern biology, there is one question that this work, despite its name, largely fails to address: How can natural selection give rise to distinct species, unable to interbreed, when this reproductive failure can hardly be an advantage? To address this question, I use simple models to explore what happens when two genetically distinct populations or species come into contact and interbreed to form hybrids. Sometimes, these hybrids can do really well and even outcompete their parents in certain environments. In other cases, the hybrids may suffer from infertility or increased mortality. Yet another possibility is that rare hybrid individuals facilitate the exchange of advantageous genes between the parental lineages, facilitating their adaptation. Studying the interactions between genes, I shed light on the probability of each of these outcomes and what they may tell us about the history of the species from which these genes originate.