When people go hiking these days, all kinds of gadgets can help guide their way. But historically, humans used something a lot more low-tech: a pile of rocks.

The piles, technically called cairns, have marked trails for millennia, but in recent years, these stones have become steeped in controversy.

To Beth Dinet, stacking stones provides "an overwhelming sense of peace, and connecting with onenness."

As she builds a pile at a popular swimming hole — and "spiritual vortex" — near the New Age hub of Sedona, Ariz., she searches for rocks with the right smoothness, flatness and metaphysical energy. She tops it with a white rock, sparkling with a bit of crystal. Nearby, others have built dozens of other cairns.

"When someone else walks this path, and they see these rocks, they know that, 'Hey, someone else experienced maybe the same thing or had the same thought as I did when I was out here,' " says Dinet. "So it's a unity."

That's not the feeling they inspire in Robyn Martin, a lecturer focusing on ecological oral histories at Northern Arizona University. She experiences something a bit more aggressive.

"Yes, I have knocked a few down, sure," she says, adding that she considers the cairns "pointless reminders of human ego."

"There are so many different ways to express yourself, and to be out in these wilderness areas with your family or by yourself, where you don't have to leave a reminder for somebody else to find that you were there," she says.

Through the years, she says, she's seen cairns go from being navigational tools to becoming a kind of backcountry fad, popping up like mushrooms.

Martin's irritation isn't just about aesthetics. Moving rocks alters the landscape, she says, causing erosion and evicting insects from their homes. They can also confuse hikers, leading them astray.

She recently wrote as much in an essay featured on the website for High Country News magazine. Some commenters agreed with Martin, but others were blistering: "Go murder some kale," "get a life," "#istherearockshortage."

Author David B. Williams says he turned up similar passion while researching his 2012 book Cairns: Messengers in Stone.

He says that national parks have been inundated by these towers of rock, from Maine to California to Hawaii — and that careless cairns go against the very nature of the stone columns, which Williams says have been used on every continent to convey critically important messages.

"This is a way to go, this is a way to avoid; this is a way to appease a deity, this is the way to honor the dead," he says.

That said, given that humans have felt compelled to construct these piles for millennia, he understands why people continue to.

Dinet says she understands the argument against building cairns, but feels her little pillar shouldn't be compared to graffiti or litter.

"There's worse things in life that you could do to make yourself feel good than stack some rocks," she says.

And so the fad continues, one stone at a time.

Copyright 2015 KJZZ