Identifying humans’ oldest animal relatives provides insights into the genetics of evolution



Early evolution in animals and the molecular innovations that drove increased diversity (and complexity) is only partly understood. One of the main knowledge gaps relating to those early yet critical events was the lack of whole-genome sequencing data from the last non-bilaterian animal phylum without a sequenced genome: Ctenophora, or the comb jellies.


IRP researchers led by Andy Baxevanis, Ph.D., sequenced and analyzed the genome of a comb jelly, Mnemiopis leidyi, and found that comb jellies, which possess complex cell types such as neurons and muscle cells, are our oldest animal relatives—even predating the sponge, a simple animal without complex cell types. Interestingly, the group’s studies also show that a surprising number of genes implicated in human disease can be identified in the earliest animals, and that these early branching animal species may be ideal model organisms for investigating developmental processes inherent to all animals.


The use of comparative genomic techniques to study the comb jelly genome has shed light on what physical and structural features were present in the earliest animals, providing a new way of thinking regarding early animal evolution and evolutionary adaptation. These studies have also provided a solid foundation for looking beyond the traditional set of organisms currently used as experimental models, as basic biological discoveries arising from even our most distant animal relatives have great potential to give us keen insights about the human genome, as well as lay the groundwork for translational studies focused on specific human diseases.


Ryan JF, Pang K, Schnitzler CE, Nguyen AD, Moreland RT, Simmons DK, Koch BJ, Francis WR, Havlak P; NISC Comparative Sequencing Program, Smith SA, Putnam NH, Haddock SH, Dunn CW, Wolfsberg TG, Mullikin JC, Martindale MQ, Baxevanis AD. (2013). The genome of the ctenophore Mnemiopsis leidyi and its implications for cell type evolution. Science. 342(6164).

Maxwell EK, Schnitzler CE, Havlak P, Putnam NH, Nguyen AD, Moreland RT, and Baxevanis AD. (2014). Evolutionary profiling reveals the heterogeneous origins of classes of human disease genes: implications for modeling disease genetics in animals. BMC Evol. Biol. 14, 212.