A study says that the peculiar sleeping patterns of humans may have contributed to the power of our minds, reports The New York Times.

But it was not easy for our monkey-like ancestors to reach REM sleep. They slept on branches, and their nights were anything but easy. As monkeys try to sleep today, they get roused by winds, tree snakes and the jostling of their fellow primates.

“It’s like economy class on a plane,” said Dr. Samson. Monkeys, he believes, have to rest longer to get the benefits of REM sleep.

The fossil record suggests that 20 million years ago, the ancestors of humans and other apes changed their sleeping habits because they became too big for branches. Today, no primate that weighs over 60 pounds sleeps on a branch. Instead, chimpanzees, bonobos and their cousins build sleeping platforms each night from sticks and other materials.