January 13, 2009

Hunting Larger Game Affects Evolutionary Process

A new study shows that hunting and harvesting plants and animals creates an evolutionary development that causes them to decrease in size and reproduce sooner.

"As predators, humans are a dominant evolutionary force," said Chris Darimont of the University of California, Santa Cruz. "It's an ideal recipe for rapid trait change."

Researchers announced on Monday that their investigations of the hunting and fishing of 29 diverse species indicates that with human influence, critters have decreased 20 percent in size and their reproductive age moves forward 25 percent.

Darimont and researchers measured the speed of trait alteration with a system named "Darwin," after Charles Darwin, who created the concept of natural selection to clarify the theory of evolution.

They investigated modifications in fish size, limpets, snails, bighorn sheep and caribou. They also looked at two plants: the Himalayan snow lotus and American ginseng.

In practically every case, the species hunted by humans decreased in size and began reproducing sooner, causing the animal populations to become exposed to more dangers.

"Earlier breeders often produce far fewer offspring. If we take so much and reduce their ability to reproduce successfully, we reduce their resilience and ability to recover," Darimont stated.

Their notes align with additional studies that imply that several kinds fish are over-harvested.

"The public knows we often harvest far too many fish, but the threat goes above and beyond numbers," Darimont said in a statement. "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator."

Rules intended to shield the young could actually aid in driving this deviant course, Darimont said.

"Hunters are instructed not to take smaller animals or those with smaller horns. This is counter to patterns of natural predation, and now we're seeing the consequences of this management," he noted.

The study is published in the Proceedings of the National Academy of Sciences.


On the Net: