Although I also disagree with the GP, I think phrasing evolution as an optimization process is a mistake. Evolution is a diversification process that exploits variation within a population to make the population as a whole more resilient to changes in the fitness function.
The net result is the same -- even if Klotho production is neutral in the fitness landscape, you would expect it to be quite common. For it to be naturally as rare as it is probably implies a significant fitness cost in other ways.
It could very well be, however, that the particular problems with Klotho production are factors which are no longer relevant in the current fitness landscape, but we (and other animals) evolved a certain resistance to Klotho production that has yet to be overcome by the irrelevance of the underlying costs. For example, if Klotho production significantly reduced reaction times or the time it takes to ramp up adrenaline production, then it might be that we are at a point where the downsides are no longer as relevant as they once were.
The net result is the same -- even if Klotho production is neutral in the fitness landscape, you would expect it to be quite common. For it to be naturally as rare as it is probably implies a significant fitness cost in other ways.
It could very well be, however, that the particular problems with Klotho production are factors which are no longer relevant in the current fitness landscape, but we (and other animals) evolved a certain resistance to Klotho production that has yet to be overcome by the irrelevance of the underlying costs. For example, if Klotho production significantly reduced reaction times or the time it takes to ramp up adrenaline production, then it might be that we are at a point where the downsides are no longer as relevant as they once were.