Researchers at the University of St Andrews have discovered a key genetic change that likely allowed animals with backbones to develop greater complexity. By examining sea squirts, lampreys, and frogs, they found that certain genes began producing far more protein variations during the transition to vertebrates. This finding, published in BMC Biology, sheds light on the origins of diverse tissues and organs in species from fish to humans.
The study, conducted by scientists at the University of St Andrews, reveals an important evolutionary milestone in the development of vertebrates, which include mammals, fish, reptiles, and amphibians. Published on February 2, 2026, in the journal BMC Biology, the research highlights how signaling pathways—essential for cell communication during embryo formation and organ development—evolved to support increased biological complexity.
To investigate this, the team generated new genetic data from sea squirts, an invertebrate species, a lamprey as an early vertebrate, and a frog. Sea squirts provided a baseline for non-vertebrate animals, while lampreys and frogs helped identify changes specific to backbone-bearing species. Using innovative long-molecule DNA sequencing, a method applied for the first time to these animals' relevant genes, researchers mapped the full spectrum of transcripts and proteins produced by signaling output genes.
The analysis showed a striking surge in protein diversity: unlike the sea squirt, both the lamprey and frog generated many more versions of proteins from these genes, exceeding patterns seen in most other genes. This expansion in protein forms likely enabled cells to specialize into a wider array of tissues and organs, driving the diversification of vertebrate life from simpler ancestors.
Lead author Professor David Ferrier from the School of Biology noted the unexpected nature of the discovery: "It was very surprising to us to see how this small selection of very particular genes stands out in the way that they are behaving compared to any other sort of gene we looked at. It will be exciting to determine how these various different protein forms work in distinct ways to generate the diversity of cell types we now see in vertebrates."
These insights not only clarify vertebrate origins but also hold potential for medical applications. Understanding these pathways could inform strategies for disease treatment, given their role in growth and links to conditions like cancer when disrupted.