Recently I have been reviewing some fly fishing literature; historical and contemporary and I came to the conclusion that, logically, everything that one can say about fly fishing has been said in one form or another.
Let's take fly casting for just one example. Fly casting consists of a rod, which is nothing but a tapered flexible lever. This flexible lever is used to propel a line which, in the modern situation, is tapered and specifically weighted to be used with a specific lever. When timed properly the flexible lever transmits energy to the line in such a manner as to propel the line toward at a specific target. The skill with which this is performed is primarily caused by the individual flexing the lever. If we go back to the very earliest recognized documents that address the issue of fly fishing we find that the rods were tapered levers that were used to propel a tapered line constructed of horsehair and deliver it to a specific target. While this form of casting was fundamentally different than what constitutes fly casting today the basic concept remains unchanged. Since those earliest descriptions of fly casting reams of paper have been consumed describing this basic act. Over the intervening years the equipment has changed and the form has been refined but the basic principles of physics behind the act of casting have remained the same. [Force equals Mass times Acceleration] In reality we are not "casting the fly" we are casting the line and the fly goes along for the ride.
All of this to say that whatever we can say about fly casting has already been said. Nothing coming in the future will change the basic physics of fly casting. We have books, videos, and diagrams ad nauseam describing how to use a flexible lever to propel a weighted line toward a target. Logically speaking it has all been said.
The same could be said about leaders that are used to connect the weighted line to the fly. The materials have changed but the basic principles of physic have not and will not change with the discovery of some new type of material. Tapered horsehair and silk gut leaders used the same principles of physics as modern nylon leaders. We can change the formula for the taper, use stiff or limp material [and there are scientific reasons behind that as well], but the principles behind what makes it work remain unchanged.
One of the more interesting things that I realized in my review of fly fishing concerns the fly. Pick up any fly pattern book and critically look at the various flies; nymphs, emergers, wet flies, dries and streamers. If you spend enough time looking through the various pattern books one thing will start to emerge; there are only so many ways to tie the same type of fly. Flies still consist of a hook, thread, and various types of material that is secured to the hook using tread. The materials and methods have changed but basically there is little difference between the modern fly and the first one tied by someone name Aelianus. Near the end of the 2nd Century he described the practice of Macedonian anglers on the Astraeus River using artificial flies to catch fish.
"They fasten wool round a hook, and fit on the wool two feathers that grow under a cocks wattles, and which in color are like wax. Their rod is six feet long, and their line is the same length. Then they throw their snare, and the fish, attracted and maddened by the color, come straight at it, thinking for the pretty sight to gain a dainty mouthful; when, however, it opens its jaws, it is caught by the hook, and enjoys a bitter repast, a captive."
Sounds very much like the description that one might find in a modern fly tying book about how to tie a fly and what material to use but this description was written nearly 2,000 years ago.
Each new generation of fly fishers presume that they have discovered something new when they tie a fly on the end of a leader and drop it into the water but they are really only repeating something untold numbers of others have done before them. Fly fishing is really a tale as old as time.