megalithic phase independently arose all lie in most natural sea
connection with each other, while not one is in the interior of Europe.

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 a