A reader writes:
Art De Vany describes the Pareto Principle as "the most unusual events will have the greatest impact." That is actually backwards. The Pareto Principle is really: the events with the greatest impact will tend to be the most unusual. The subtle difference is the direction of causality. The way De Vany states this, it sounds like all unusual events have a large impact – which, of course, is ridiculous.
The Pareto Principle is essentially a version of a power law. Think: earthquakes, or forest fires, or wealth distribution, etc. The largest earthquakes are the most rare, and small ones happen all the time. Similarly, the population of the very rich is not just smaller than other levels of wealth; it is exponentially smaller.
What utter bollocks.
First off, that's not the Pareto principle ("… states that, for many events, roughly 80% of the effects come from 20% of the causes." – wiki). Second off, you can't just take a rule from one domain (economics) and apply it to another unrelated one (exercise). Let's apply Einstein's relativity to child rearing or set theory to mixing drinks while we're at it.
Thirdly, you cease getting fitness improvements due to lack of progressivity in your workout, not because you don't have "unusual" elements in your workout (and if you're doing max effort every single workout, then max effort is no longer "unusual", is it?). Lyle Mcdonald has an excellent series of articles explaining the different training zones and the bodies' physical adaptations. With some number fudging, maybe it's more like 40% of the work can get get you 80% of the effects, the real Pareto principle can be stretched to accommodate exercise, but not the "unusual" version put forth by De Vany.
Oh, and fourthly on the subject of De Vany's book and his claim that we're virtually unchanged since our ancient ancestors, look at the book The 10,000 Year Explosion: How Civilization Accelerated Human Evolution. We have accumulated many genetic differences that are advantageous to living in densely populated, agricultural based societies.