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Extract from BBC News page

By Prof Adam Hart
University of Gloucestershire

Are humans inadvertently driving evolution in animals?

Mounting evidence suggests activities such as commercial fishing, angling and hunting, along with the use of pesticides and antibiotics, are leading to dramatic evolutionary changes.

Some well understood examples of unnatural selection and evolution come from commercial fisheries. It is the larger fish that are usually targeted and those that remain are consequently smaller. But crucially this effect isn't just a demographic change.

Dr Eric Palkovacs from the University of California Santa Cruz explains: "We have removed the large fish and that has a direct effect on the size structure of a population.

Subsequent populations will feel that impact because those smaller fish contribute more genes to the population." In other words, the genes for "smallness" prosper while genes for "largeness" are selectively removed by fishing.

Not only are the fish evolving to be smaller but they also are evolving to become sexually mature at a younger age. This is because those fish that have genes causing later maturity are likely to be harvested before they have the chance to breed, removing those genes from the population.

The selection pressure and evolution caused by fishing can have wider ecosystem consequences.
Atlantic cod that used to be several metres long are now only a metre or so, which, points out Palkovacs, means "we basically have an organism that once was top predator in the system and now serves as prey to other organisms.

When we fish and hunt we aren't acting like natural predators. We are relentless, ruthlessly efficient "super predators" taking out the biggest and best. Similarly, when we change the environment we do so on a grand scale.
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