For biologists, the quintessential which-came-first debate is not chicken or egg, but rather, sponge or ctenophore. The argument over which of these groups represents the earliest branch from the ancestor of all animals has raged for more than a decade, with heated arguments coming from both sides. Now, a new chromosome-level ctenophore genome published in the November volume of G3 Genes|Genomes|Genetics may offer the opportunity to settle once and for all whether the Porifera or the Ctenophora evolved first. “One method that could possibly resolve the phylogenetic position of ctenophores and sponges is comparing whole-chromosomes,” the researchers wrote in their paper.
With their lack of true tissues and organs or even symmetry, sponges might seem like the obvious choice for the oldest animal group. But starting back in the early 2010s, a vocal group of researchers armed with genomic data began to argue that despite their apparent complexity, ctenophores (commonly ...
