Superpredators: Evidence humans have sped up evolution process

The biologists estimate that hunting has caused such characteristics as body size and reproductive age to change at a rate that is a staggering 300 per cent above the pace that would prevail in nature. This figure is even greater than the change attributed to other human interferences, such as pollution, which was estimated to alter species 50 per cent faster than what normally happens.

The human approach is the opposite to what happens in nature, where predators kill the easiest-to-catch animals, such as the young, the old and the sick, but are unable to take out the fittest adults, which then reproduce and pass their desirable characteristics on to future generations.

THE DIMINISHING PREY

BIGHORN SHEEP

The sheep, found in mountainous areas of Western Canada and the United States, are famed for the unusual curved horns on the rams. The rams are hunted as trophies, but researchers believe the practice of taking the biggest specimens has prompted genetic change leading to a marked decline in horn size.

CARIBOU

Caribou from southern Norway, the last remaining wild population in Europe, have shrunk because of hunting. The selective killing of the biggest animals has led to a reduction in the size of bodies, antlers and jaws. Researchers suspect the same trend may have occurred in southern populations of caribou in Canada.

AMERICAN GINSENG

The gnarled root of the plant is prized for its medicinal properties - collected for illnesses ranging from cancer to Alzheimer's disease. But extensive harvesting has led to a change in the composition of wild stands, with an increased number of smaller, non-reproductive plants.

COD

The destruction of cod stocks has led to altered reproductive behaviour. The fish produce eggs at a younger age, but this early breeding has a big drawback. The early breeders are producing abnormally low numbers of eggs.