The Theory of Leylines

Regular routes are believed to have been first laid down or used in the Neolithic period of the Stone Age. Before that, man had been a hunter and his movements were governed by the movements of his prey. These might even have followed migratory patterns as animals moved from summer to winter grazing or hunting grounds and back again. But now man's life-style was becoming comparatively more sophisticated as he became more sophisticated as he became more self-reliant, choosing to farm rather than hunt and this brought about more permanent settlements and a more settled way of life. Travel was now for a different purpose. To trade for salt or flint, to fight, to expand his territory or knowledge of his area.
His travelling would now be done in a more logical manner and might even have had a religious or superstitious basis. What is important to remember is that Neolithic man did not have a road system to follow. The traveller in those times had to ensure he had made mental notes of the distance travelled, the direction and the salient features of his route. After all, he had to find his way back again!

We are taught at school that the shortest distance between two points is a straight line. The theory of straight line travel is interesting. Most people with average balance can walk in a straight line with their eyes closed. There is also a theory that there is a virtually redundant part of the human brain that acts as a compass by detecting the earth's magnetic field and that such a part is still very much active in some species such as migrating birds and large aquatic animals.
I doubt whether prehistoric man or pigeon ever knew which direction they were travelling in relation to a compass, but I am sure that they both knew when they were straying from their initial line, such deviation being sensed by balance, which is necessary when turning left or right and by the brain's magnetic sensor when deviating from a given line at a slower rate.

If one can imagine being the first person to go into a specific area with no previous knowledge of that area, one can imagine how ley lines might have been formed. A man in that position would automatically head from high ground to high ground so as to get the maximum views of the countryside for the simple reason it gave him fore-knowledge of what might be in his path, such as lakes, rivers or other natural features which might hinder or help him in his progress.
As he became more familiar with the territory, he might have supplemented his surveying with signs of his own, such as mounds of earth or stone, earthen walls he might build for his own security or shelter, clearings where he might make a temporary home and as an area became more populated, so the number of places of importance would increase and subsequently, the number of ley lines.