From the beginning of human history people have dragged any load too heavy to be carried. But large objects are often of awkward shape and texture, liable to snag on any roughness in the ground. The natural solution is to move them on a platform with smooth runners - a sledge.
Wooden sledges are first known, by at least 7000 BC, among communities living by hunting and fishing in northern Europe, on the fringes of the Arctic. It is possible that they use dogs to pull them, but the technological advance is valuable even without animal power. On icy ground a man can move a heavy load on a sledge with relatively little effort.
The domestication of cattle, and more particularly the discovery that a castrated bull becomes the docile but very powerful ox, means that humans can transport heavier loads than before. This is done at first on sledges, which slither adequately over the dry grass of the steppes of southern Russia and on the parched earth of Mesopotamia. In both regions ox-drawn sledges are in use by the 4th millennium BC.
The natural next stage is the addition of wheels.
The wagon: 3000 BC
A wagon gets stuck in the mud, more than 5000 years ago, near what is now Zürich. It has two pairs of solid wooden wheels, each attached to an axle which turns with them. The wagon is massively heavy (perhaps about two thirds of a ton, or 700 kg) and it is irretrievably stuck. It stays where it is. It is now one of the earliest known examples of wheeled transport.
Whether first developed as an 'invention' in one place, or re-invented in several, wheels seem to have evolved as a natural solution to the problem of transport in areas where both oxen and wood are available. By 2000 BC heavy wheeled transport is in use in a region stretching from northern Europe to western Persia and Mesopotamia.
The wheels of the first wagons are made either from a single piece of wood or from three joined planks; sometimes they turn on the axle, sometimes with it. Speed is not the main characteristic of such a vehicle, as anyone will know who has seen bullock carts on the farm roads of India today. Even so, during the third millennium BC wagons acquire a regal status in addition to their practical uses. They can only transport the king on his throne at about two miles per hour in a public ceremony, but royal tombs reveal that both wagon and oxen are valued enough to be required in the next world.
For even greater glamour, and far greater speed, two new elements are needed - the horse and a spoked wheel.
Horse and chariot: from 2000 BC
The horse is available in Mesopotamia by about 2000 BC. Not much later a two-wheeled chariot is developed. Its superstructure is made of a light wood, and its wheels are not solid; their rims are of bent wood, held in place by spokes. A horse can pull a chariot at a trot at up to 8 miles an hour - and at a gallop twice as fast.
Here is a vehicle in which a ruler or noble can cut a fine ceremonial dash. There are chariots among the treasures in the tomb of Tutankhamen. The wheels are stacked separately, not only because of the cramped space in the tomb. They are so delicate that the weight of a stationary chariot will distort their rims.
In subsequent centuries, up to relatively recent times, travel improvements are mainly limited to transport on the sea. They are the result of larger ships (which can venture further afield) and of better methods of navigation.
On land one large new beast of burden is domesticated - the camel. But the main improvement in classical times derives from the construction of roads, first in the Persian and then in the Roman empire.
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