I was sitting next to my friend on a bus the other day. He farted. It got us thinking: How many farts have there been in human history?

We thought the best way to go about this was to estimate the number of farts per day and multiply that by the number of aggregate days that people have lived. The "farts per day" figure we used was 13.6, a number obtained in a study by gastroenterologist Michael Levitt (who, in this 1995 article, presciently noted that 99 percent of the smell comes from 1 percent of the fart). While this number has doubtlessly varied throughout history, it was the only empirical data we could find.

The "aggregate days" figure was a bit more difficult to obtain. We derived our estimate from a paleodemographical study by the Population Reference Bureau, which estimated that 108 billion people have ever been born. The tough part is figuring out the average life expectancy of these people. As a very rough estimate, we assumed that everyone born before 1900 had an average lifespan of 30 and everyone after 1900 had an average lifespan of 45. The latter figure was lowered to account for the 7 billion people who are still living. Based on the PRB's estimate of when births occurred, this gave us a weighted average of 32 years.

The final estimate: 13.6 farts per day x 365 days in a year x 32 years per human birth x 108 billion births = 17 quadrillion farts ever.

Humanity has farted around 17 quadrillion times. Here's to 17 quadrillion more.