Earth’s days were once 2 hours longer — and that may have triggered one of the biggest evolutionary explosions in history, study suggests

Earth's days were once more than two hours longer than they are now, thanks to the moon drifting thousands of miles farther away in its orbit over two periods, researchers have discovered.

The extra hours of sunlight, in turn, may have led to oxygenation events that ushered in a period when life's complexity exploded, the study researchers say.

"Daylength changes may influence the distribution of solar energy and temperature gradients, potentially impacting weather systems and atmospheric dynamics," the researchers wrote in the new study, published Aug. 6 in the journal PNAS.

Nowadays, the moon orbits at an average of 238,855 miles (384,400 kilometers) from Earth. But our satellite hasn't always been where it is now.

Related: Earth is wobbling and its days are getting longer — and humans are to blame

Earth's days are currently around 24 hours long, but that wasn't always the case. Over time, the moon tugs on our planet. As it does so, it migrates away from Earth, siphoning away its kinetic energy. As a result, our planet's spin around its axis slows, thus lengthening Earth's days, according to the study.

Modeling changes in how Earth wobbles as it spins can give a rough picture of this slowdown over the planet's History. But this estimate is clearly flawed, because it leads to a prediction that Earth and the moon would have collided around 1.5 billion years ago, the study authors noted.