In time the vast majority of the megalithic monuments of Europe seem to begin near the end of the neolithic period and cover the copper age, the later forms continuing occasionally into that of bronze. Here again it is curious that megalithic building, if merely an independent phase in many countries, should arise in so many at about the same time, and with no apparent reason. Had it been the use of worked stones that arose, and had this followed the appearance of copper tools, the advocates of this theory would have had a stronger case, but there seems to be no reason why huge unworked stones should simultaneously begin to be employed for tombs in many different countries unless this use spread from a single source.
For these reasons it is impossible to consider megalithic building as a mere phase through which many nations passed, and it must therefore have been a system originating with one race, and spreading far and wide, owing either to trade influence or migration. But can we determine which?
Great movements of races by sea were not by any means unusual in primitive days, in fact, the sea has always been less of an obstacle to early man than the land with its deserts, mountains, and unfordable rivers. There is nothing inherently impossible or even improbable in the suggestion that a great immigration brought the megalithic monuments from Sweden to India or vice versa. History is full of instances of such migrations. According to the most widely accepted modern theory the whole or at least the greater part of the neolithic population of Europe moved in from some part of Africa at the opening of the neolithic age. In medieval history we have the example of the Arabs, who in their movement covered a considerable portion of the very megalithic area which we are discussing.
On the other hand, many find it preferable to suppose that over this same distance there extended a vast trade route or a series of trade routes, along which travelled the influences which account for the presence of precisely similar dolmens in Denmark, Spain, and the Caucasus. Yet although much has been written about neolithic trade routes little has been proved, and the fact that early man occasionally crossed large tracts of land and sea in the great movements of migration does not show that he also did so by way of trade, nor does it prove the existence of such steady and extensive commercial relations as such a theory of the megalithic monuments would seem to require. Immigration is often forced on a race. Change of climate or the diverting of the course of a great river may make their country unfit for habitation, or they may be expelled by a stronger race. In either case they must migrate, and we know from history that they often covered long distances in their attempt to follow the line of least resistance. Thus there is nothing a priori improbable in the idea that the megalithic monuments were built by a single invading race.
There are other considerations which support such a theory. It will be readily admitted that the commonest and most widely distributed form of the megalithic monument is the dolmen. Both this and its obvious derivatives, the Giant's Grave, the allée couverte, and others, are known to have been tombs, while other types of structure, such as the Maltese temple, the menhir, and the cromlech, almost certainly had a religious purpose. It is difficult to believe that these types of building, so closely connected with religion and burial, were introduced into all these regions simply by the influence of trade relations. Religious customs and the burial rites connected with them are perhaps the most precious possession of a primitive people, and they are those in which they most oppose and resent change of any kind, even when it only involves detail and not principle. Thus it is almost incredible that the people, for instance, of Spain, because they were told by traders that the people of North Africa buried in dolmens, gave up, even in isolated instances, their habit of interment in trench graves in favour of burial in dolmens. It is still more impossible to believe that this unnatural event happened in one country after another. It is true that the use of metal was spread by means of commerce, but here there was something to be gained by adopting the new discovery, and there was no sacrifice of religious custom or principle. An exchange of products between one country and another is not unnatural, but a traffic in burial customs is unthinkable.
Perhaps, however, it was not the form of the dolmen which was brought by commerce, but simply the art of architecture in general, and this was adapted to burial purposes. To this there are serious objections. In the first place it does not explain why exactly the same types of building (e.g. the dolmen), showing so many similarities of peculiar detail, occur in countries so far apart; and in the second place, if what was carried by trade was the art of building alone, why should the learners go out of their way to use huge stones when smaller ones would have suited their purpose equally well? That the megalithic builders knew how to employ smaller stones we know from their work; that they preferred to use large ones for certain purposes was not due to ignorance or chance, it was because the large stone as such had some particular meaning and association for them. We cannot definitely say that large stones were themselves actually worshipped, but there can be no possible doubt that for some reason or other they were regarded as peculiarly fit to be used in sanctified places such as the tombs of the dead. It is impossible that the men who possessed the skill to lay the horizontal upper courses of the Hagiar Kim temple should have taken the trouble to haul to the spot and use vast blocks over 20 feet in length where far smaller ones would have been more convenient, unless they had some deep-seated prejudice in favour of great stones.
Such are the main difficulties involved by the influence theory. On the other hand, objections have been urged against the idea that the monuments were all built by one and the same race. Thus Dr. Montelius in his excellent Orient und Europa says, "In Europe at this time dwelt Aryans, but the Syrians and Sudanese cannot be Aryans," the inference being, of course, that the European dolmens were built by a different race from that which built those of Syria and the Sudan. Unfortunately, however, the major premise is not completely true, for though it is true that Aryans did live in Europe at this time, there were also people in Europe who were not Aryans, and it is precisely among them that megalithic buildings occur.
The French archæologist Déchelette also condemns the idea of a single race. "Anthropological observations," he says, "have long since ruined this adventurous hypothesis." He does not tell us what these observations are, but we presume that he refers to the occurrence of varying skull types among the people buried in the megalithic tombs. Nothing is more natural than that some variation should occur. We are dealing with a race which made enormous journeys, and thus became contaminated by the various other races with which it came in contact. It may even have been a mixed race to start with. Thus even if we found skulls of very different types in the dolmens this would not in the least disprove the idea that dolmen building was introduced into various countries by one and the same race. It would be simply a case of the common anthropological fact that a race immigrating into an already inhabited country becomes to some extent modified by intermarriage with the earlier inhabitants. The measurements given in the last chapter would seem to show that despite local variation there is an underlying homogeneity in the skulls of the megalithic people.
It thus seems that the most probable theory of the origin of the megalithic monuments is that this style of building was brought to the various countries in which we find it by a single race in an immense migration or series of migrations. It is significant that this theory has been accepted by Dr. Duncan Mackenzie, who is perhaps the first authority on the megalithic structures of the Mediterranean basin.