Thousands of species are currently polyploid, and contain multiple copies of their genome. On the other hand, the long-term establishment of organisms that have undergone ancient whole genome duplications (WGDs) has been exceedingly rare. The apparent paucity of ancient genome duplications and the existence of so many species that are currently polyploid provides a fascinating paradox. Interestingly, many ancient WGDs seem to have been established at very specific times in evolution, for instance during major ecological upheavals and periods of extinction. Our work has shown that WGDs observed for many different plant lineages seem to have coincided with the most recent major mass extinction, i.e. the K/Pg extinction, 66 million years ago. I will put forward different hypotheses of why polyploids, compared to their diploid progenitors, might have had some selective advantage that might explain their survival at times of extinction or environmental turmoil. Also, I will discuss how WGD events might lead to an increase in biological complexity. WGDs copy entire pathways or networks, and as such create the unique situation in which such duplicated pathways or networks could evolve novel functionality through the coordinated sub- or neofunctionalization of its constituent genes. I will describe a remarkable case of coordinated gene expression divergence following WGDs in Arabidopsis thaliana. We identified a set of 92 homoeologous gene pairs that all show a similar pattern of tissue-specific gene expression divergence following WGD, with one homoeolog showing predominant expression in aerial tissues and the other homoeolog showing biased expression in tip-growth tissues (root-tip and pollen-tube).