Virtually all climate research in peer-reviewed science journals predicts global temperatures will gradually rise by several degrees in coming decades, accompanied by swings of extreme cold and heat.
"But just because we've seen a large evolutionary response, that doesn't mean a natural population can adapt to climate change with no consequences," Barrett told AFP Thursday.
About 95 per cent of the fish population died during the three-year study, with only five per cent developing a tolerance for cold," he said. "The consequences of losing 95 per cent might be catastrophic, because the remaining five per cent might not be able to sustain the population," said Barrett. He added: "We don't know the genetic basis of this trait."
The rapid evolution by the marine fish in the study mirrored the 10,000-year-long evolution of freshwater stickleback in British Columbia - descendants of marine fish trapped inland at the end of the last Ice Age, who evolved to live in extreme cold.
Barrett noted that humans also evolved over some 10,000 generations, since their first migration from Africa, raising the question of how many generations it might take for northern peoples to evolve genes that could cope with warmer climates experienced by their African ancestors."You can start to draw a parallel in evolutionary rates," said Barrett.