What happens when you dump an ocean fish into a freshwater lake?
That experiment has been performed naturally tens of thousands of times over millions of years as sea-faring threespine sticklebacks — which, like salmon, travel up rivers to spawn — have gotten stranded in lakes and had to evolve as permanent denizens of fresh water.
Michael Bell, currently a research associate in the University of California Museum of Paleontology at UC Berkeley, stumbled across one such natural experiment in 1990 in Alaska, and ever since has been studying the physical changes these fish undergo as they evolve and the genetic basis for these changes. He has even created his own experiments, seeding three Alaskan lakes with oceanic sticklebacks in 2009, 2011 and 2019 in order to track their evolution from oceanic fish to freshwater lake fish. This process appears to occur within decades — very unlike the slow evolution that Charles Darwin imagined — providing scientists a unique opportunity to actually observe vertebrate adaptation in nature.
The upshot of these 31 years of research is a study, published Friday, June 18, in the journal Science Advances, that details the