In 1997, Arthur Weis found himself with an extra bucket of seeds. Weis, who was teaching at the University of California at Irvine at the time, had dispatched a student, Sheina Sim, to gather some field mustard seeds for a study. When Sim was done with her research, Weis was left with a lot of leftover seeds. For no particular reason, he decided not to throw the bucket out. “We just tossed it in a cold, dry incubator,” said Weis.
Weis is glad they did. When a severe drought struck southern California, Weis realized that he could use the extra bucket of seeds for an experiment. In 2004 he and his colleagues collected more field mustard seeds from the same sites that Sim had visited seven years earlier. They thawed out some of the 1997 seeds and then reared both sets of plants under identical conditions. The newer plants grew to smaller sizes, produced fewer flowers, and, most dramatically, produced those flowers eight days earlier in the spring. The changing climate had, in other words, driven the field mustard plants to evolve over just a few years. “It was serendipity that we had the seeds lying around,” says Weis.
Weis is convinced that his experiment is just a harbinger of things to come. Global warming is projected to drastically raise the average global temperature, as well as producing many other changes to the world’s climate, such as more droughts in California. And in response, Weis and other researchers contend, life will undergo an evolutionary explosion.
“Darwin thought evolution was gradual, and that it would take longer than the lifetime of a scientist to observe even the slightest change,” says Weis, who is now at the University of Toronto. “That might be the average case, but evolution can also be very rapid under the right conditions. Climate change is going to be one of those things where the conditions are met.”