CAPE TOWN (REUTERS).- A group of prehistoric people mastered a difficult and delicate process to sharpen stones into spears and knives at least 75,000 years ago, more than 50,000 years earlier than previously thought, according to a report.

This technique, known as pressure flaking, allowed for the more precise shaping of stones to turn them into better weapons for hunting, a paper published on Thursday in the U.S. periodical Science said.

"These points are very thin, sharp and narrow and possibly penetrated the bodies of animals better than that of other tools," said Paola Villa, a curator at the University of Colorado Museum of Natural History and a study co-author.

The new findings show pressure flaking took place at Blombos Cave in what is now South Africa during the Middle Stone Age by anatomically modern humans and involved the heating of silcrete -- quartz grains cemented by silica -- used to make tools, the university said in a news release.

Pressure flaking is a process by which implements previously shaped by hard stone hammer strikes followed by softer strikes with wood or bone hammers are carefully trimmed on the edges by directly pressing the point of a tool made of bone on the stone, it said.

"Using the pressure flaking technique required strong hands and allowed toolmakers to exert a high degree of control on the final shape and thinness that cannot be achieved by percussion," Villa said.

Prior to the Blombos Cave discovery, the earliest evidence of pressure flaking was from the Upper Paleolithic Solutrean culture in France and Spain roughly 20,000 years ago.

The authors speculated the pressure flaking technique may have been invented in Africa and used sporadically before its later, widespread adoption in Europe, Australia and North America.

The co-authors included Vincent Mourre of the French National Institute for Preventive Archaeological Research and Christopher Henshilwood of the University of Bergen in Norway and director of the Blombos Cave excavation.

"This flexible approach to technology may have conferred an advantage to the groups of Homo sapiens who migrated out of Africa about 60,000 years ago," the authors wrote in Science.

(Editing by Ralph Boulton)