AT SOME POINT IN THE HISTORY of civilization, shepherding gave way to farming. That created a need for some way of keeping cows and pigs from wandering freely through the meadows. The fence was born. Wooden fences were among the earliest, but they are expensive and time-consuming to build. By 1870 smooth cable was easy to get hold of and came into wide use on ranches. Cattle would rub their back on the wire, and sometimes one would slip through. Eventually the herds caught on.