Darts were pretty much used worldwide even in Paleolithic times.

Some of the earliest evidence of advanced tool use includes remnants of an early type of dart, which can be considered the ancestor of arrows as well as bows. Reconstructions of this system have a range of over one hundred meters (yards) and can penetrate several centimeters of oak. This technology was used worldwide from the Upper Palaeolithic (late Solutrean, ca. 18,000-16,000 BC) until the development of archery made it obsolete.

http://www.reference.com/browse/wiki/Dart_%28missile%29

The Atlatl made the dart the high tech weapon until the bow came along. http://www.donsmaps.com/atlatl.html

From New Scientist 15 May 1999 pp 40-43(Same page, near the bottom -

One reason Perkins objects to the term 'spear thrower' is that it gets in the way of understanding how the atlatl really works. Some of the first archaeologists to experiment with atlatls tried to throw rigid spears, and managed only poorly aimed shots that flew just 45 metres. They concluded that only constant practice from childhood would have allowed any one to use the weapon effectively. In fact, a beginner can start to hit targets, large ones at least, after just an hour's practice.

So how does the atlatl work? The thrower holds the atlatl and dart parallel to one another and horizontal, with elbow bent and the hand just beside the ear. There's an initial forward motion with the shoulder, then the elbow straightens and finally the wrist flicks the atlatl forward with an action not unlike that of an overexuberant fly fisherman trying to lure a trout. The atlatl accelerates the rear of the dart through an arc, with a movement similar to that of an ancient ballista flinging boulders against the enemy.

That's the obvious part. What isn't so obvious is how the projectile springs away from the tip of the atlatl. In the early tests, the rigid spears were reluctant to part company with the atlatl. So, all too often, at the end of the throw, as the atlatl tip began to move downwards it would drag the back end of the spear down too, ruining accuracy - an effect called kickdown. (Some Inuits use atlatl like sticks to launch rigid harpoons. But these are launched downward from boats, and the kickdown effect doesn't make much difference.)

A flexible dart, by comparison, springs away from the atlatl tip. You can think of the dart as a spring, which is compressed by the initial force of the throw. The dart releases this stored energy at the end of the throw by pushing off the atlatl tip before the tip begins moving downwards.

Perkins also analyses the dart in terms of wave mechanics (see Diagram). At the start of the throw, the dart bends as the acceleration pushes against the mass of the stone tip. A wave propagates from the rear of the dart to its tip. When the wave reaches the tip, it is reflected back again.

At the rear, the force generated by the still accelerating atlatl rein forces this wave and sends it once more towards the dart tip, where it reflects again.

When the wave reaches the rear this time, however, the atlatl has stopped accelerating, and the wave's energy strikes the atlatl tip and propels the dart forward. 'The wave goes through a cycle of harmonic oscillations, gaining a tremendous amount of energy as the dart's speed is increased,' Perkins explains. It's this energy, he argues, that makes most of the difference between the 45 metres that a rigid spear will travel and the 200 metre flight of a flexible dart.