New light on old civil­i­sa­tions

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

Mail & Guardian - - News - Matthew du Plessis

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.

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