Variation in North American dart points and arrow points when one or both are present

The appearance of the bow and arrow in North America as a weapon-delivery system is predicted to have prompted an increase in variation among antecedent projectile points that tipped darts propelled by atlatls. Attributes of dart points are expected to display greater variation with the appearance of the bow as prehistoric artisans experimentally sought points that worked effectively as arrow points. Attributes of arrow points are predicted to also initially display much variation. Subsequent to the initial burst of variation, less-effective variants of attributes were winnowed out, causing a reduction in variation of attributes of both dart points and arrow points. Both coefficients of variation for individual attributes and summed coefficients of variation for multiple attributes of three sequences of projectile points from evolutionarily independent areas in North America confirm these predictions.