This is a trilobite on the left. Poor thing died out 252 million years ago. On the right is a horseshoe crab. They’re ancestral cousins of trilobites and still roam New Jersey shores:

One big thing changed over time: Trilobites had dozens of legs, all of which were tiny feet whose only purpose was walking. Crabs have fewer legs, but each has a specialized use. Strong hind legs are used for walking, big claws fight prey, smaller one grab food, tiny ones give partners a special crab hug while mating.

The path from “many things” to “a few really useful things” is one of evolution’s signatures.

Samuel Williston was a 19th-century paleontologist who first noticed a historic trend in the reduction of body parts. Primitive animals often had many duplicate body parts, then evolution reduces the number but increases their usefulness. “The course of evolution has been to reduce the number of parts and to adapt those which remain more closely with their special uses, either by increase in size or by modifications of their shape and structure, Williston wrote in 1914.

Animals with hundreds of teeth often evolved to have a handful of specialized incisors, canines, and molars. Dozens of jawbones fuzed into two big ones. Skulls often made up of hundreds of tiny bones evolved into typically fewer than 30.

Evolution figured outs its version of simplification. It (if you can imagine it talking) says, “Get all that useless crap out of the way. Just give me the few things I need and make them really effective.”

The question, then, is why complexity sells in the modern world.

And, oh, does it sell. Particularly when the product is advice, volume is associated with usefulness. A tweet can be more insightful than a book, but people pay $20 for books and would never pay a cent for thousands of tweets. Investment banking analysts create 100-page pitchbooks that no one – no one – reads, but clients still request. A few years ago a trend of reducing your financial plan to an index card flew around financial circles, but the brevity was popular for its usefulness, not salability. Charge a client for ten sentences of advice and they’ll leave in disgust. Give them a phone-book-size elaboration and they’ll pay you a fortune and refer their friends.

Sometimes length is necessary. When the Allies met to discuss what to do with Germany after World War II Winston Churchill noted, “We are dealing with the fate of eighty million people and that requires more than eighty minutes to consider.”

But computer scientist Edsger Dijkstra once wrote:

Simplicity is the hallmark of truth— we should know better, but complexity continues to have a morbid attraction. When you give for an academic audience a lecture that is crystal clear from alpha to omega, your audience feels cheated and leaves the lecture hall commenting to each other: “That was rather trivial, wasn’t it? The sore truth is that complexity sells better.

The sore truth is that complexity sells better.

Why?

Why do complexity and length sell when simplicity and brevity will do?

A few reasons.

1. Simplicity feels like an easy walk. Complexity feels like mental CrossFit.

If the reps don’t hurt when you’re exercising, you’re not really exercising. Pain is the sign of progress that tells you you’re paying the unavoidable cost of admission. Short and simple communication is different. Richard Feynman and Stephen Hawking could teach math with simple language that didn’t hurt your head, not because they dumbed down the topics but because they knew how to get from A to Z in as few steps as possible. An effective rule of thumb doesn’t bypass complexity; It wraps things you don’t understand into things you do, like a baseball player who – by keeping a ball level in his gaze – knows where the ball will land as well as a physicist calculating the ball’s flight with precision.

The problem with simplicity is that the reps don’t hurt, so you don’t feel like you’re getting a mental workout. It can create a preference for laborious learning that students are actually OK with because it feels like a cognitive bench press, with all the assumed benefits.

2. Length is often the only thing that can signal effort and thoughtfulness.

The U.S. constitution is 7,591 words. A typical business management book covering a single topic is perhaps 250 pages, or something like 65,000 words.

The funny thing is the average reader does not come close to finishing most books they buy. Even among bestsellers, average readers quit after a few dozen pages. Length, then, has to serve a purpose other than providing more material. My theory is that length indicates the author has spent more time thinking about a topic than you have, which can be the only data point signaling they might have insight you don’t. It doesn’t mean their thinking is right. And you may get enough of their thinking after two chapters. But the purpose of chapters 3-16 is often to show the author has done so much work that chapters 1 and 2 might have some insight. Same for research reports and white papers.

3. Things you don’t understand create a mystique around people who do.

If you say something I didn’t know but can understand I might think you’re smart. If you say something I can’t understand I might think you have an ability to think about a topic in ways I can’t, which is a whole different species of admiration. When you understand things I don’t I have a hard time judging the limits of your knowledge in that field, which makes me more prone to taking your views at face value.

4. Complexity gives a comforting impression of control, while simplicity is hard to distinguish from cluelessness.

In most fields a handful of variables dictate the majority of outcomes. But only paying attention to those few variables can feel like you’re leaving too much of the outcome to fate. The more knobs you can fiddle with – the 100-tab spreadsheet, or the Big Data analysis – the more control you feel you have over the situation, if only because the impression of knowledge increases. The flip side is that only paying attention to a few variables while ignoring the majority of others can make you look ignorant. If a client says, “What about this, what’s happening here?” and you respond, “Oh, I have no idea, I don’t even look at that,” the odds that you’ll sound uninformed are greater than the odds you’ll sound like you’ve mastered simplicity.

Williston once recognized that no body part, once lost to evolution, will ever come back. New organs can arise, and those that remain adapt and change. But once nature finds a way to do more with less, the cast is set, you’re never going back. “A characteristic once lost is lost forever,” he wrote.