Evo-devo scientists investigate how animal embryos develop, which allows them to make inferences about evolutionary change. In other words, they look at the interaction of genes, cells, tissues, and the environment during embryonic development to glean how differences in those factors may lead to evolutionary change over many generations, such as the transformation of a fish fin into a vertebrate limb.

Andrew Gillis, who is joining MBL as an associate scientist later this summer, likens evo-devo to a form of comparative developmental biology. "Instead of focusing on studying one animal," says Gillis, "you are comparing how different animals develop in order to understand how changes in development have led to changes in adult form."

The Gillis lab focuses on the earliest events in vertebrate evolution, like the origins of fins, gills, and jaws. In order to understand which features were present in our oldest vertebrate ancestors, the lab studies a wide variety of vertebrates from far-flung branches of the evolutionary tree. By seeing whether features are shared between all of the animals, they can infer which ancestors in the evolutionary tree may have had those features.

Evo-devo has seen waves of excitement following technological advances since its early days in the late 19th century, when scientists began searching for clues about evolutionary trends by peering into slices of embryos using histology and microscopy. Interest in evo-devo piqued again with advances in molecular biology that allowed scientists to piece together information about genes and gene expression during development. In recent years, the field has experienced yet another rebirth as tools for editing and sequencing genomes have advanced alongside new microscopy techniques. Despite evo-devo's long history, "there are old questions that still remain largely unanswered," explains Gillis.