Wednesday, July 8, 1998 Published at 15:40 GMT 16:40 UK
The oldest gifts in the world
Africa's great Rift valley
Excavations from a rock shelter in the central Rift Valley of Kenya offer the best evidence yet that modern human behaviour originated in Africa 40,000 years ago. Our science editor Dr David Whitehouse reports.
Archaeologists have found stone-tools in a rock cave called Enkapune Ya Muto.
The tools have been dated at at least 46,000 years old, possibly as old as 50,000 years. This is the oldest evidence of primitive man's stone tool technology.
But also in the cave and only slightly younger, at 40,000 years, are beads. They are the oldest ornaments ever discovered.
The ornaments are important because of what they imply about the behaviour of humankind 40,000 years ago. They imply gifts, some form of art and reward in a social setting.
Some scientists believe that the ancient beads suggest that early man was forging a closer society in difficult environments.
Others believe the beads may be the earliest example of a primitive currency.
The research is described in the Journal of Archaeological Science.