The epigenetic phenomenon of genomic imprinting, whereby the maternally and paternally inherited copies of a gene are differentially expressed, has long intrigued both theorists and empiricists. In particular there has been a great deal of interest in understanding why such a peculiar pattern of gene expression has evolved, and what implications it has for our understanding of evolutionary processes. This special issue presents a series of papers that have addressed these fundamental questions through various approaches. We aimed in these papers for the latest data to better inform and test the various theories for the evolution of imprinting, perhaps suggesting modifications to existing theories or the development of new ones.
