Scientists Have Observed Evidence of Evolution in Real Time

tetrapod evolution, illustration
30-Year Snail Study Reveals Evolution in Real TimeMARK GARLICK/SCIENCE PHOTO LIBRARY - Getty Images
  • A 30-year-long study of a small population of marine snail shows how evolution can adapt to environmental changes quite rapidly.

  • This study revealed how a specific ecotype of the snail changed its shape within only a few generations and rapidly developed genetic mutations thanks to its high genetic variation.

  • This rare, in-the-wild experiment shows the importance of high genetic variation and preserving diverse habitats so species can develop those evolutionary protections.


Evolution is often thought of as the slow work of millennia upon millennia, subtly altering genomes as species slowly adapt to environmental changes or pressures generation after generation. This makes evolutionary study particularly difficult, as it’s not easy to note changes—or even predict future mutations—in most animal populations. But sometimes, the conditions to study evolution at work are just right.

Take, for instance, the species of marine snail known as Littorina saxatilis. This snail is well-known for being a particularly difficult species to identify—not because it’s hard to find, but because it can be found in so many shapes, sizes, and colors. In fact, it’s been labeled the “most misidentified creature in the world,” as it’s been erroneously identified as a “new species” more than 113 separate times since its first description in 1792.



However, it’s because of this species’ ability to quickly adapt to its unique marine environment that Swedish marine ecologist Kerstin Johannesson sensed an opportunity in the early 1990s. When a toxic algal bloom decimated islands and skerries (small rocky islands) off the west coast of Sweden in 1988, Johannesson decided to use the reintroduction of the snails as an opportunity to study evolution in real time. Across the entire species of L. saxatilis, there are two particular ecotypes—genetically different organisms within the same species—known as Crab-ecotypes and Wave-ecotypes, the differences between which in both appearance and behavior are particularly striking. While Wave snails inhabit skerries along this stretch of coastline, both Crab and Wave snails occupy the nearby shore.

So, when Johannesson reintroduced the species to the area, she specifically placed specimens of the Crab ecotype on a skerry and set off a 30-year experiment to see how the population adapted to its new environment. The results of that study were published today in the journal Science Advances.

“Our colleagues saw evidence of the snails’ adaptation already within the first decade of the experiment,” Diego Garcia Castillo, a graduate student at the Institute of Science and Technology Austria and co-author of the study, said in a press statement. “Over the experiment’s 30 years, we were able to predict robustly what the snails will look like and which genetic regions will be implicated. The transformation was both rapid and dramatic.”



Changes were apparent in the snail population after only a few generations due to a phenomenon known as “phenotypic plasticity,” which allowed the Crab-ecotype to rapidly change its shape and adapt to its new environment. However, the ecotype’s “rapid and dramatic” transformation was also genetic and aided, in part, by the diverse gene pool of L. saxatilis.

Because the snails experienced similar conditions in the recent past, low prevalence genes were essentially lying in wait for specific conditions to reoccur. Once the snails found themselves in that familiar environment, they accessed that genetic information, which in turn fueled rapid evolution. Scientists have known that high genetic variation makes a species particularly suited to adapt to a changing climate, but few studies have been conducted in real time in the wild.

This study perfectly showcases why efforts to protect a wide range of habitats are vital—so that species can maintain their genetic variation. Right now, a thriving, 30-year-old population of 1,000 Crab-ecotype snails off the western coast of Sweden provides a powerful example of what is possible if we do protect these wondrous natural spaces.

You Might Also Like