Here’s a real Zeitgeist of a story for you: not only is it strong evidence in favour of the theory of evolution by selective pressure, but it also shows that external forces – including human intervention – can accelerate the process to a great degree.

The big downside, however, is that it may be a sign that one of the largest fisheries in the world is about to collapse like a house of cards: you see, there’s a gene in cod which governs the depth at which they prefer to live, and relentless trawling has exerted evolutionary pressure in favour of the mutant fish which swim deeper than the others. [image by Hello, I am Bruce]

Fisheries are known to exert selective pressure on fish. In some cases this has led to the evolution of smaller fish.

This was thought to be a slow process. “Previous workers have concluded that evolutionary changes are only observable on a longer timescale, of decades,” Árnason says. “The changes we observe are much more rapid.”

The A gene is being driven out simply because of where those fish choose to live, says Árnason. Such inadvertent, rapid selective pressure may drive some fisheries to crash.

“Man the hunter has become a mechanised techno-beast,” the team writes. “Modern fisheries are uncontrolled experiments in evolution.”

Worryingly, the researchers found that cod in the Icelandic fishery are becoming sexually mature while still smaller and younger. Something similar occurred in Newfoundland cod just before that fishery crashed. “We think this too is an evolutionary response to the selective pressure of fisheries,” says Árnason.

So, bad news… but bad news with some valuable knowledge in its back pocket. If extreme external conditions apply evolutionary pressure, where will we see this phenomenon crop up next? Perhaps, if the environmental uber-pessimists turn out to be right, we humans will end up at the pointy end of evolution’s goad; on a planet with limited food and water and numerous existential hazards, who knows what we might turn into over the course of a century or two?