Anthropologist David Graeber thinks we could do without half our jobs.

A few years ago, someone snuck into the London Underground and plastered several hundred guerilla posters over ads. The posters read things like "Huge swathes of people spend their days performing tasks they secretly believe do not really need to be performed ... It's as if someone were out there making up pointless jobs for the sake of keeping us all working.

These quotes came from David Graeber, an anthropologist at the London School of Economics. In his new book, "Bull*** Jobs: A Theory," (the book spells the whole word out, but we Treehuggers are not nearly as crass as London professors) he claims that that, over the last century, farm and industrial jobs disappeared dramatically, while "professional, managerial, clerical, sales," grew to 75 percent of U.S. and British employment. A lot of these are what he calls "bull****" jobs. People working them will be the first to tell you that their jobs make no contribution to the world ... other than, perhaps, destroying the environment.

"Half of work could probably be eliminated with no deleterious effects," Graeber said. "A lot of what’s called growth isn’t, it’s just pointless make-work."

During the 2008 crash, Graeber began suspecting that a number of people have jobs that provide nothing useful to the world (and often aren't even useful to their companies).

"It made me think of all the energy — not just human energy but power — running all these offices where people aren’t doing anything," he told me. Lighting, heat, air conditioning and electricity run all day in offices. Not to mention the oil, steel and other resources that go into everything from constructing office building to making office supplies, or the cars, trains and buses that bring people to their jobs every day.

"Presumably they would be doing something if they were not at work, but it would almost certainly not be so destructive of resources," Graeber added.

So he asked people who considered their jobs "bull****" to write to him. Tons of people responded, including corporate lawyers, telemarketers and school administrators, explainging that their jobs were pointless. Graeber even described one organization with a plumber who never fixes anything. So the organization hired another man to go around apologizing for the plumber.

"This review was written at the desk of a salaried office job, where I am paid $65,000/yr to do virtually nothing important, so I mostly sit in my chair and listen to podcasts and audiobooks all day," writes one "Bull**** Jobs: A Theory" reviewer. "It turns out, I'm not alone."

Graeber expected about 20 percent of people to consider their jobs bull****. But as it turned out, 40 percent of people surveyed in Britain and the Netherlands think their jobs shouldn't exist. Perhaps it's no surprise that only around 33 percent of American workers are "involved in, enthusiastic about and committed to their work and workplace," found Gallup.

This isn't just annoying. It's destructive. All these jobs contribute to environmental destruction. According to Graeber, the single best way to help the planet may be to slow down the economy. This may sound like heresay, but Graeber points out that the idea of a constantly growing economy is "quite a recent thing."

"The whole idea of using growth as an economic indicator only goes back to the 60s," he said. "It was banks that pushed it ... They somehow convinced us that there has to be more stuff than there was last year and there has to be more money than there was last year."

The idea that the economy must keep growing is common, but it's actually pretty weird.

"It’s not an assumption that people had for most of history. It’s not a natural assumption," he said. "But everybody just takes it for granted now."

Our current economy is indeed set up for growth. Interest is attached to just about everything, meaning that people lose jobs and businesses crumble without growth. But there are alternatives.

"You can have an economy that’s negative growth on paper where people are actually living better," Graeber said. He pointed out that happiness comes more from free time, not work.

"If you’re working less and have more time, then you can have more fun," he said. A slower economy would require a way to distribute the basics of life — food, housing, transportation, medicine, extras — without relying on everyone fighting each other for pointless jobs. Americans work plenty — eight hours a day on average — but it's unclear whether their work actually accomplishes much.

"We’re caught in this vicious circle that we’re working all the time," Graeber added. "So we can’t imagine what we’d do when we aren’t working because we don’t have time to sit around and imagine."