Canadian scientists have uncovered what they say is the first unequivocal evidence that prehistoric North Americans hunted and butchered now-extinct horses.

University of Calgary scientists discovered the pony-sized horses while excavating the dry bed of the St. Mary Reservoir in southern Alberta.

The site is one of the richest archeological fields in North America. It is now protected under the Alberta Historical Resources Act.

The discovery adds weight to the theory that overhunting played a major role in the extinction of North American horses about 10,000 years ago.

The University of Calgary team also found footprints of woolly mammoths and a now-extinct North American camel.

The site provides "an astonishingly detailed picture of what the New World was like during the late Pleistocene Era," said University of Calgary archeologist Dr. Brian Kooyman. "We can't believe how lucky we are."

The link between the Equus conversidens horse and human hunters was established after team members unearthed a skeleton of an extinct horse at the site. Several of the horse's vertebrae were smashed and it had what appeared to be butcher marks on a number of its bones.

Some 500 metres from the skeleton, they also discovered several Clovis spearheads. Protein residue testing and examination of the spearheads confirmed the artifacts had been used to hunt the extinct horse.

Although archaeologists have long suspected the "big game" hunters of the Clovis period (9000-10000 BC) of hunting the horses, there has been little evidence to support this theory until now.

Spanish Conquistadors reintroduced horses to the Americas during the 16th century.