Fossilized cell structures identify an ancient origin for the teleost whole-genome duplication

Some lineages of organisms have undergone major evolutionary radiations, while others have not. Establishing why is a central goal of evolutionary research. Whole-genome duplication (WGD) is often proposed as having caused the spectacular evolutionary radiation of teleost fishes. However, due to the absence of genetic data for fossil species, it has been impossible to pinpoint precisely when WGD occurred during teleost history. We use three-dimensional measurements of fossilized bone cell spaces to estimate genome sizes in extinct species, observing a near doubling of size during earliest teleost ancestry. This suggests that WGD occurred very early, substantially predating the dramatic radiation of teleosts. These findings suggest at most an indirect link between WGD and teleost diversification.