I'm convinced that the invention of the automobile has led to a great deal of unhappiness. After a steady stream of technological precursors, the automobile finally freed man from the last bonds of daily toil. And he hasn't been happy since.
There's something decidedly uncomfortable about driving a car and working in an office. Ask yourself, "Does it feel right?" Muscles have been evolving on Earth for hundreds of millions of years, only to be tossed aside as obsolete in the last hundred. This is not how the vast majority of human beings, much less mammals, have felt as they lived out their lives. The discomfort of driving extends to the mind. Automobiles allow us to escape from our environment to an insular and artificial one. But we are very much not free inside a car; we are much of the time stuck helplessly in traffic and all of the time compelled to think about driving. Lastly, physical strength was one thing that made men useful to women. I would be willing to bet there's an inverse correlation between marriage longevity and use of an automobile. Do women not agree that easy life has left men altogether less necessary than they once seemed to be? And man did this to himself!
The answer to the problem is not to freeze technology—progress is an inspiring and beautiful thing. Our transportation paradigm is critical to our economic output, which gives us the food and medicine to survive, and the science and technology to explore the cosmos. No, the answer will require far more creative and subtle ways of integrating physical and mental struggle.