Photo Credit: Katie Davis Koehn
Evolution is often thought of as a process that produces different solutions to the challenges of survival. But new research suggests that nature may repeat some of its genetic solutions more often than scientists previously recognized.
The study, published in the Proceedings of the National Academy of Sciences, found evidence of identical genetic changes in distantly related jellyfish lineages separated by more than 600 million years.
This phenomenon, known as molecular convergence, occurs when unrelated or distantly related species independently develop the same genetic changes. In simple terms, evolution can arrive at the same genetic solution more than once, even when species have been evolving separately for hundreds of millions of years.
The research was conducted by scientists at the University of California, Santa Barbara (UCSB), the University of Kansas, Texas A&M University, and the University of Nebraska.
"We’re studying molecular evolution here — to what extent similar genetic changes occur in different organisms,” said Cory Berger, a postdoctoral researcher in the laboratory of Todd Oakley, a UCSB biologist and principal investigator at the Marine Science Institute. “And that in particular is something we don’t know much about.”
Investigating Evolution’s Repeated Patterns
To understand how often evolution produces similar outcomes, the researchers examined Medusozoa, an ancient group that includes jellyfish and their relatives. These animals have evolved over approximately 650 million years, with different lineages independently developing features such as eyes and repeatedly losing the free-swimming medusa stage.
“We’re studying this particularly old group of animals that has some interesting convergent phenotypes that we already know about,” Berger said.
The team wanted to determine whether species that independently evolved similar physical features also shared similar genetic changes. To investigate, the researchers reconstructed the evolutionary relationships among jellyfish using fossil and molecular evidence, then compared genes expressed in different species.
“We sequenced all the genes that in these different jellyfish, all the genes that are expressed, at least in theory,” said Oakley. “And then we looked at the patterns of change across those genes. If the same specific change has happened in distantly related species, then we’re calling that convergence.”
The analysis revealed an unexpectedly high number of repeated genetic changes, including some among lineages that had been evolving independently for more than 600 million years.
The amount of genetic similarity indicates that at the genetic level, evolution may be more repeatable and maybe therefore more predictable than we expected. But it also means that we still have a huge amount to learn about how the genes function, how that plays out on the whole-organism scale.
The Same Genes, Different Outcomes
One of the study’s most surprising findings was that repeated genetic changes did not consistently correspond to similar physical traits.
This distinction is important. Two species may develop similar features, such as eyes, through different genetic pathways. Conversely, the same genetic change can occur in different species without producing the same physical result.
Genes work within complex biological systems, and their effects can depend on other genes and environmental conditions. As a result, similar genetic changes do not always translate into similar characteristics.
“The amount of genetic similarity indicates that at the genetic level, evolution may be more repeatable and maybe therefore more predictable than we expected,” Oakley said. “But it also means that we still have a huge amount to learn about how the genes function, how that plays out on the whole-organism scale.”
The findings suggest that evolution may reuse certain genetic solutions more often than previously thought, even though the physical outcomes can differ. Understanding how these molecular changes influence entire organisms remains an important question for future research.
The research team also included Marina I. Stoilova and Paulyn Cartwright of the University of Kansas, Rebecca M. Varney of the University of Nebraska, Maria Pia Miglietta of Texas A&M University, and Sam C. Abrams of UCSB.
Adapted from original reporting by Sonia Fernandez, “Adaptive molecular convergence more common than previously thought,” The Current, UC Santa Barbara, 2026.