It will be useful first of all to recall some dates: 1848—the Communist Manifesto; 1859—Contribution to a Criticism of Political Economy, in the introduction to which Marx made his clearest definition of the materialist conception of history. It was also the year of Origin of Species and the authentication of Boucher de Perthes’ handaxes. ‘Relics of bygone instruments of labour possess the same importance for the investigation of extinct economical forms of society as do fossil bones for the determination of extinct species’ . This quotation is from the first volume of Capital published in 1867, which Marx had wished to dedicate to Darwin; Darwin declined the honour. We know from the chapter ‘The Part Played by Labour in the Transition from Ape to Man’ in Engels's Dialectics of Nature, written in the 1870s but published posthumously 40 years later, that Engels had been thinking about prehistoric man, although he evidently had not got very far beyond Marx's description of labour in Capital.