Rapid Evolution of Many Species Due to Humans

A study at the University of California, Santa Cruz has shown that human sports hunting and fishing has forced changes in size and reproduction of many species as much as 300% faster than would occur naturally.

Researchers reviewed 34 previous studies stretching back two decades that tracked 29 different species across 40 different geographic systems. They found that human influences such as hunting and fishing have produced game animals 20% smaller than previous generations, and the age at which they first reproduce is 25% earlier than previous generations. In effect, humans act as "super-predators" on other species, dominating their natural evolutionary track.

That species can change due to human influence is not a new concept; the entire industry of animal husbandry consists of human-bred species. What scientists found remarkable in this study is the speed at which human predation can modify native wild species. These changes are found to occur 50% faster than those brought about by pollution, loss of habitat or introduction of foreign species. The study found changes in animals as small as fish and snails and as large as caribou and bighorn sheep.

Whereas a wolf may prey upon 20 other species, humans essentially prey upon hundreds of thousands. And whereas a wolf will prey upon the smaller and weaker individuals, advancing the natural selection of prey species, humans select the largest and strongest, forcing species' evolution in the opposite direction.

These results were published on January 12th online edition of the Proceedings of the National Academy of Sciences.

Photo: LiveScience