The Use of Iron Tools and Mortar closed the
Megalithic Era in a Locality

(5) Here and there the art of hewing and erecting these enormous stones has been preserved to our own time, or close to our own time. But it is always in isolation, whither the echo of the march of civilisation cannot reach, far amongst the mountains, as in the Khasi Hills in Assam, or in solitary islands of the Pacific like Easter Island, where it is conjectured by some that the making of the colossal busts was continued up till about the eighteenth century. At most points on the route the art has been lost in prehistoric times, probably in neolithic times before either bronze or iron tools were thought of. It is not unlikely that the discovery of the metals and of mortar led to its abandonment. With the fine edge that the new implements would take, men could afford to cut smaller and more manageable blocks, and graves as well as houses could be more easily built without the aid of multitudes of workmen. When there were no wheeled vehicles or draught animals, these megalithic structures meant vast masses of labour disciplined like slaves to drag the great stones long distances and to set them erect in the earth. For some of them weigh between three and four hundred tons, and stand fifty or sixty feet above the ground. And most of them are at least several tons in weight and a dozen feet in height.