Although Boucher de Perthes was the first to establish that Europe had been populated by early man, he was not able to pinpoint the precise period, because the scientific frame of reference did not then exist. Today the hand axes of the Somme River district are widely accepted to be at least 500,000 years old and thus the product of Neanderthal populations, while some authorities think they may be as old as one million years and therefore associated with "Homo erectus".