Way back before electricity gave us lights and, in turn, extended the day’s activities past sundown, people relied on the moon to show them the way. When the moon was full, people could take advantage of the moonlight for all sorts of things, from extra work to fun with friends or even spiritual pursuits.

But did Edison’s big invention change our sleeping patterns? Or are we hardwired to follow the moon’s phases?

University of Washington researchers went to remote Argentina to track the sleep patterns of indigenous people in three communities. One group had no electricity, a second had limited access to electricity and the third was in an urban area with full access to electricity.

Using wrist monitors, they tracked the residents’ sleep patterns over two lunar cycles, around 29 days each.

All of the study participants showed the same sleep oscillations as the moon progressed through its cycle. In all three communities, people stayed up later and got less sleep during the nights three to five days leading up to a full moon.

To test their findings, the researchers analyzed sleep-monitoring data from nearly 500 Seattle-area college students that had been collected for a separate study. They found the same oscillations among the students, who largely were unaware of how much moonlight there was on a given night.

This led them to conclude that human sleep is synchronized with lunar phases regardless of ethnic and sociocultural factors or the level of urbanization.

It’s just another reminder that, wherever we are on this planet, in the end, we’re not that different. Just a bunch of moonstruck humans rolling with the lunar tides.