Numerous recent publications have demonstrated convincingly that the most effective approach to understanding the origin of the human genome is comparative animal genomics. Similarly, to understand the origin of multicellularity and animal-specific gene families that are relevant to human development, health and complex diseases, we need to trace back these features to their ancestral unicellular eukaryotes (protists).
It is now well established that animals share a common single-celled ancestor with fungi, and that in the two sister lineages multicellularity arose independently. This insight prompts a host of intriguing, fundamental questions:
- What genome-level changes coincide with the rise of multicellularity in these two kingdoms, and to what extent are these changes different in animals and fungi?
- Which particular genes or genomic features, present in the unicellular ancestors of animals and fungi, were prerequisites for the emergence of multicellularity?
- What is the origin of animal- and fungal-specific gene families?
Clearly, an incisive comparative genomics analysis requires genomic information from very early diverging animals and fungi, as well as their specific unicellular relatives.