Research in the Leys lab focuses on the evolution of animal features by studying sponges. Sponges are widely considered the most ancient lineage of multicellular animals, and seem to show elements of an early nervous system, tissues and organs, and polarity – characteristics which are shared by all other animals (which are often called ‘Eumetazoa’ or ‘true animals').
From our perspective, sponges are not just ‘almost animals’ (parazoa) but fully fledged animals that are highly adapted to a suspension feeding lifestyle. Perhaps they became the ultimate suspension feeder by ‘losing’ aspects of more complex tissues, organization, and genes. The hypothesis that ctenophores may be basal to sponges (i.e. have arisen earlier than sponges) could be seen in this light, suggesting that sponges lost the complexity present in the last common ancestor of sponges and ctenophores.