Unsurprisingly, people's butts were particularly uneven tanners — compared to test subjects' backs, for example, they were initially much more resistant to tanning, and then when they did "get some color" it wasn't as much as in other areas of the body. In other words, if you've got a pasty posterior, it's a better idea to slather on the self-tanner than the baby oil. But you knew that already, right?
Another good reason not to bake? That perfectly even golden glow is actually impossible for most people. Researchers from the University of Edinburgh found that some areas of the body are much more resistant to tanning than others — meaning people often overexpose themselves in a cycle of attempting to "even out" their tan.