New light on old civilisations

Scientists are remapping the stories of ancient civilisations by shooting them with lasers

Mapungubwe, where the Shashe river meets the Limpopo, the Inca Empire of South America, the Kingdom of Greater Zimbabwe and the Mayan city states of Mesoamerica are some of the civilisations that once held dominion over all they surveyed, but whose worlds have since been lost to changing climates or sickness, or outright theft by colonial invaders.

Archaeological digs have shed light on many aspects of how these peoples may have lived and ruled: how they ordered their lives and their communities, how they farmed, worked and worshipped — and (with greater enthusiasm than you’d probably expect) where they put the lavatories.

But new understanding is being gained and startling discoveries made as new ways of looking at these precursor societies emerge.

One of these ways is to shoot lasers at them.

Archaeologists can only get their dig on if they know where to look, and that’s where the lasers come in. The trick, you see, is to shoot them from the sky.

A bird’s eye view used to be the best eye view you could hope to have when out ruin-detecting. It can bring an otherwise unassuming bunch of rocks into focus as man-made structures. For example, thanks to an eagle-eyed drone enthusiast, the Unesco World Heritage Site of Brú na Bóinne in County Meath, Ireland, now has a brand-new ancient henge.

But the bird’s eye view — from plane or drone or even satellite— has its limits, and can too easily be thwarted by two or three overly foliaged trees and a bit of hedge.

Which brings us back to the one thing better for archaeology than a bird’s eye view: a bird’s eye view with LASERS.

Lidar, a portmanteau of laser and radar, is a method of surveying objects or a landscape by bathing them in laser light and then measuring the reflection of the pulses. Varying the spectrum of light allows for an extraordinary level of 3D topographical detail, especially in infrared, which can reveal structures otherwise concealed by vegetation.

In 2012, documentary filmmakers and gung-ho adventurer-explorers Steve Elkins and Bill Benenson rented a Cessna, strapped some lasers to it and went hunting for the legendary Lost City of the Monkey God in the Honduran rain forest.

Would you believe they found it? Well, they found something, anyway.

In 2015, Elkins led a follow-up expedition on foot, a joint United States-Honduran venture. Deep in the jungle, they confirmed the discovery of extensive man-made structures: irrigation canals, plazas, earthworks and even a pyramid.

And now, using this same technique but on a much grander scale, researchers have discovered more than 60 000 previously undocumented man-made structures hidden in the jungles of northern Guatemala.

In research published in the journal Science on September 28, the team, led by Marcello Canuto of Tulane University in New Orleans, has revealed that the extent of agricultural engineering of the wetland areas is far greater than previously suspected.

Their lidar survey covered more than 2000km2 of what is now the densely forested region of Petén, Guatemala. But it once formed a key lowland province of the Mayan civilisation that stretched from as far back as 2000 BCE to as late as the turn of the 18th century.

The Petén Basin was the last bastion of the Mayan defence against Spanish conquistadors, but the region was already in decline when its last city was taken by the invaders in 1697. It was then abandoned, and fell to ruin and the encroaching jungle.

By shooting the place up with lasers, Canuto’s team has shown that, when it was at its height in the 8th century, Petén was home to as many as 11-million people, and threaded with an elaborate network of roadways connecting cities, towns and villages — some of them remarkably far-flung. In the researchers’ analysis, this discovery compels a revaluation of Mayan demography, agriculture and political economy.

Now, with Mayan basins filled with new understanding, the Lost City of the Monkey God found, and Celtic heritage sites re-henged, it’s perhaps time for archaeologists to consider focusing their lasers on the Limpopo valley. Let the mapping of Mapungubwe and the zapping of Greater Zimbabwe begin.