The origin of these peoples was an academic question; but for the understanding of their revolt their present social and political differences were important, and could only be grasped by looking at their geography. This continent of theirs fell into certain great regions, whose gross physical diversities imposed varying habits on the dwellers in them. On the west the parallelogram was framed, from Alexandretta to Aden, by a mountain belt, called (in the north) Syria, and thence progressively southward called Palestine, Midian, Hejaz, and lastly Yemen. It had an average height of perhaps three thousand feet, with peaks of ten to twelve thousand feet. It faced west, was well watered with rain and cloud from the sea, and in general was fully peopled.
Another range of inhabited hills, facing the Indian Ocean, was the south edge of the parallelogram. The eastern frontier was at first an alluvial plain called Mesopotamia, but south of Basra a level littoral, called Kuweit, and Hasa, to Gattar. Much of this plain was peopled. These inhabited hills and plains framed a gulf of thirsty desert, in whose heart was an archipelago of watered and populous oases called Kasim and Aridh. In this group of oases lay the true centre of Arabia, the preserve of its native spirit, and its most conscious individuality. The desert lapped it round and kept it pure of contact.
The desert which performed this great function around the oases, and so made the character of Arabia, varied in nature. South of the oases it appeared to be a pathless sea of sand, stretching nearly to the populous escarpment of the Indian Ocean shore, shutting it out from Arabian history, and from all influence on Arabian morals and politics. Hadhramaut, as they called this southern coast, formed part of the history of the Dutch Indies; and its thought swayed Java rather than Arabia. To the west of the oases, between them and the Hejaz hills, was the Nejd desert, an area of gravel and lava, with little sand in it. To the east of these oases, between them and Kuweit, spread a similar expanse of gravel, but with some great stretches of soft sand, making the road difficult. To the north of the oases lay a belt of sand, and then an immense gravel and lava plain, filling up everything between the eastern edge of Syria and the banks of the Euphrates where Mesopotamia began. The practicability of this northern desert for men and motor-cars enabled the Arab revolt to win its ready success.
The hills of the west and the plains of the east were the parts of Arabia always most populous and active. In particular on the west, the mountains of Syria and Palestine, of Hejaz and Yemen, entered time and again into the current of our European life. Ethically, these fertile healthy hills were in Europe, not in Asia, just as the Arabs looked always to the Mediterranean, not to the Indian Ocean, for their cultural sympathies, for their enterprises, and particularly for their expansions, since the migration problem was the greatest and most complex force in Arabia, and general to it, however it might vary in the different Arabic districts.
In the north (Syria) the birth rate was low in the cities and the death rate high, because of the insanitary conditions and the hectic life led by the majority. Consequently the surplus peasantry found openings in the towns, and were there swallowed up. In the Lebanon, where sanitation had been improved, a greater exodus of youth took place to America each year, threatening (for the first time since Greek days) to change the outlook of an entire district.
In Yemen the solution was different. There was no foreign trade, and no massed industries to accumulate population in unhealthy places. The towns were just market towns, as clean and simple as ordinary villages. Therefore the population slowly increased; the scale of living was brought down very low; and a congestion of numbers was generally felt. They could not emigrate overseas; for the Sudan was even worse country than Arabia, and the few tribes which did venture across were compelled to modify their manner of life and their Semitic culture profoundly, in order to exist. They could not move northward along the hills; for these were barred by the holy town of Mecca and its port Jidda: an alien belt, continually reinforced by strangers from India and Java and Bokhara and Africa, very strong in vitality, violently hostile to the Semitic consciousness, and maintained despite economics and geography and climate by the artificial factor of a world-religion. The congestion of Yemen, therefore, becoming extreme, found its only relief in the east, by forcing the weaker aggregations of its border down and down the slopes of the hills along the Widian, the half-waste district of the great water-bearing valleys of Bisha, Dawasir, Ranya and Taraba, which ran out towards the deserts of Nejd. These weaker clans had continually to exchange good springs and fertile palms for poorer springs and scantier palms, till at last they reached an area where a proper agricultural life became impossible. They then began to eke out their precarious husbandry by breeding sheep and camels, and in time came to depend more and more on these herds for their living.
Finally, under a last impulse from the straining population behind them, the border people (now almost wholly pastoral), were flung out of the furthest crazy oasis into the untrodden wilderness as nomads. This process, to be watched to-day with individual families and tribes to whose marches an exact name and date might be put, must have been going on since the first day of full settlement of Yemen. The Widian below Mecca and Taif are crowded with the memories and place-names of half a hundred tribes which have gone from there, and may be found to-day in Nejd, in Jebel Sham-mar, in the Hamad, even on the frontiers of Syria and Mesopotamia. There was the source of migration, the factory of nomads, the springing of the gulf-stream of desert wanderers.
For the people of the desert were as little static as the people of the hills. The economic life of the desert was based on the supply of camels, which were best bred on the rigorous upland pastures with their strong nutritive thorns. By this industry the Bedouins lived; and it in turn moulded their life, apportioned the tribal areas, and kept the clans revolving through their rote of spring, summer and winter pasturages, as the herds cropped the scanty growths of each in turn. The camel markets in Syria, Mesopotamia, and Egypt determined the population which the deserts could support, and regulated strictly their standard of living. So the desert likewise overpeopled itself upon occasion; and then there were heavings and thrustings of the crowded tribes as they elbowed themselves by natural courses towards the light. They might not go south towards the inhospitable sand or sea. They could not turn west; for there the steep hills of Hejaz were thickly lined by mountain peoples taking full advantage of their defensiveness. Sometimes they went towards the central oases of Aridh and Kasim, and, if the tribes looking for new homes were strong and vigorous, might succeed in occupying parts of them. If, however, the desert had not this strength, its peoples were pushed gradually north, up between Medina of the Hejaz and Kasim of Nejd, till they found themselves at the fork of two roads. They could strike eastward, by Wadi Rumh or Jebel Sham-mar, to follow eventually the Batn to Shamiya, where they would become riverine Arabs of the Lower Euphrates; or they could climb, by slow degrees, the ladder of western oases--Henakiya, Kheibar, Teima, Jauf, and the Sirhan--till fate saw them nearing Jebel Druse, in Syria, or watering their herds about Tadmor of the northern desert, on their way to Aleppo or Assyria.