Transcript

3.5.26 · Smithsonian Magazine

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Speaker 1: Welcome. This is Rebecca Shore for Radio Eye and to
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day I will be reading the Smithsonian Magazine dated March
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twenty twenty six. As a reminder, Radio Eye is a
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reading service intended for people who are blind or have
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other disabilities that make it difficult to read printed material.
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Please join me now for part one of the article
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titled the Sahara Desert hasn't always been a try desolate landscape.
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Some scientists see signs it may be greening again. Petroglyphs
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on sandstone at a National park in Chad bear witness
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to wild life that once roamed the area before the
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continent's water largely receded six thousand years ago. Could it return?
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By Henry Wissmayer. An hour before dawn in a nameless
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rock pile in the world's largest hot desert, JIMMYT. Guimona
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clambered up a narrow gully. The route was hemmed by
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high walls, where uncountable centuries of weathering had cinched the
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sandstone into a rumpled reptilian skin. From its base, the
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outcropping had looked like any one of the numerous rock
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formations or hoodoos in the northwest corner of the Ennidy
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Natural and Cultural Reserve in eastern Chad, But this one,
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Guemona assured me, contained a special treasure. Though the formation's
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interior was labyrinthine, the archaeologist moved swiftly, ignoring the GPS
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coordinates stored on his phone. He had the location committed
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to memory. Rounding a scarp, Guemona stopped in front of
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a rare expanse of vertical plane where the rock ran smooth.
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Under torchlight. I could see that hundreds of figures had
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been carved into its surface. There were ostriches with lollipop heads,
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beside stick legged tirafts their necks. Comically exaggerated human forms
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stood among this crowded beastiary, and beneath them, all in
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plympses were larger etchings of elephants, older and more deeply inscribed.
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When I found it, I yelled with excitement, Gemona told me,
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casting his head lamp left and right so that the
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shapes appeared to dance across the rock face. These were
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prehistoric etchings that hadn't been mentioned in any of the
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colonial literature he'd studied, nor had Guemona received any rumor
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of their existence from the herders. Whom he often canvassed
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for information. Whoever carved them inhabited a deeper past, perhaps
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ten thousand years ago, when the creatures they depicted could
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still be found throughout North Africa. These images were ghosts
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from a time when the Sahara was green. Soon afterward,
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back at our makeshift camp, I lay on a reed
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mat in the wide open The night sky was giving
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way to sunrise after the previous evening's wind. The land
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felt deathly still. If you've ever spent a night in
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the Sahara, it's tempting to presume that it has always
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been this way. Dry, desolate, nearly empty of life. The
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intensity of the silence conjures an impression of stasis that
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is hard to reconcile with the Sahara's surprisingly erratic geological history.
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The Enegy Reserve, close to the Sudanese border, is the
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Sahara at its most spectacular. One thousand miles from the
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nearest coast, it encompasses nineteen thousand, three hundred square miles
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of a vast sandstone plateau, its periphery incized by gorges
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and ornamented with elaborate rock forests. From space, it appears
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as an inverted triangle of textured ochre against the mellow
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gold of the Saharan Sands. There are wastes here, as
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there are in any stretch of desert, barren tracts of
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gravel plain flailed by harmatan winds that hit the skin
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like a hair dryer blowing on full. Animal skeletons lie
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where they fell, half covered in sand. Yet Enidy is
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also a place of eye rubbing beauty and miraculous vitality,
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perhaps more than anywhere else in the Sahara. Its rare
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ecology makes it the ideal place to observe the desert's
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dynamism in the raw. You would have to go back
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half a billion years to chart the birth of these
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surreal rock formations. When Enide's central massif emerged from an
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ancient sea as a mantle of sandstone. It took another
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three hundred million years for Africa to unhitch itself from
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the Gondwana supercontinent. Tens of millions more until the land
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that would come to be known as Chad crossed the Equator,
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borne along on Africa's gradual day northward migration. According to
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the Earth's scientist Martin Williams, the author of when the
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Sahara was green. It was toward the end of this
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long continental journey that the Sahara came into being. Williams
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traces the desert's birth to around seven million years ago,
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when the progressive shrinkage of the Tethus Sea, the primordial
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ocean that threaded a wide channel between Africa and Eurasia,
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upended regional hydrological cycles. It was at this point that
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northern Africa began to desiccate at scale. In subsequent eons,
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this arid state didn't hold in the mid nineteenth century,
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when much of the African interior remained a mystery to
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the wider world. The German explorer Heinrich Barth returned from
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a five year journey from Tripoli to Timbuctu with tails
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and sketches of prodigious rock art galleries, including depictions of
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animals that could now only be found one thousand miles
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farther south. Similar images would later be identified across northern Africa,
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from the Atlas Mountains to the Nubian Plains. It would
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take many decades and various empirical advances before scientists were
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able to ascertain two critical findings about the region's environmental story.
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First that the Sahara had fluctuated between wet and dry
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states during the planet's current geological era, known as the Quaternary,
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which began about two point five million years ago. Second,
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that this process is cyclical, repeating over long spans of
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geological time at intervals dictated by thermodynamic forces far beyond
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human control. Changing atmospheric conditions have dragged the West African
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rain belt northward, bringing water and life to the desert
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paleo climate. Mitologists have dubbed this phenomenon. When it occurs
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a North African Humid Period or n a HP, it
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is more commonly known as the greening of the Sahara.
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Saharan petroglyphs memorialized the latest of these episodes, the Holocene
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in AHP, believed to have lasted from five thousand, five
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hundred to eleven thousand years ago. We know from lake
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ring residues that Lake Chad on the Chad Cameroon border
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was previously larger than the Caspian Sea twenty three times
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its current maximum expanse Studies of images from the Lansat
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satellite program have identified the shadows of the so called
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Sahabi rivers which once flowed from Megachad all the way
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to the Mediterranean. Large herbivores thrived in Riparian forest, big
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cats stalked expansive range lands. It was not to last.
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Around six thousand years ago, the summer rains sputtered once
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perennial wetlands turned seasonal, then dried up altogether. Vegetation withered,
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its life giving carbon carried off on the trade winds,
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an age of plenty supplanted by an age of dust.
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As the ecosystem collapsed, the megafauna, including lions, giraffes, elephants,
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and all manner of ungulates, died off or gravitated south,
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and the humans who once inscribed their likenesses onto rock
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shelters withdrew into oases and high refugia like Chad's own
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to Beesty mountains, or the congregated around the unfaltering waters
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of the Nile Valley. Ramona's tableau bore testament to one
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of the most dramatic climate shifts since the last Ice Age.
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It is a phenomenon that is believed to have shaped
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the dispersal of humans out of Africa. Now, according to
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some researchers, climate change may be causing the Sahara to
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green again millennia ahead of schedule, with consequences for ecosystems
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and human society that are difficult to forecast or comprehend.
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My week law journey into entity with Guemona, then the
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reserve's chief archaeologist, began in July twenty twenty four in
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the oasis town of Fada on the reserve's western rim.
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A low slung compound on the town's outskirts served as
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the regional headquarters for African Parks, a South Africa based
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conservation nonprofit that has managed the region on behalf of
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the Chattyan government since twenty eighteen. We embarked early one morning,
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setting off in a convoy of three land cruisers, two
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containing expedition members and support crew. The flat beds stacked
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high with tents and provisions. A platoon of park rangers
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trained in first aid, navigation, communic nation and security brought
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up the rear. The days were ferociously hot, Chad had
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endured another drought stricken year. On the two day drive
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northeast from the capital in Jemina, sullen livestock herds at
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the roadside were sacks of bones. After five consecutive years
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of severe food shortages. The United Nations World Food Program
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was launching emergency aid operations to stave off the risk
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of famine in Chad's hinterlands. But now near the peak
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of the boreal summer, annual rains were returning to the
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southern Sahara. At nightfall, lightning strobed beyond the horizons. By morning,
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temporary wetlands appeared in topographical depressions. Our introduction to Endy's
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unique geography was the Gelta Darshai, twenty five miles southeast
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of Fada. Parking at its mouth, we walked into a
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canyon bound by three hundred foot walls. The rock was
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pocked with deep caves that reeked of back guano. Standing
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water pooled along its base. Enide occupies an unusual ecological
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niche midway between sterility and abundance. Because of its ground water.
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The region sits atop the Nubian Sandstone Aquifer, the largest
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subterranean water system in the world, which extends from northeast
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Chad across some eight hundred thousand square miles in Libya, Egypt,
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and Soudan. The Lakes of Unianga, a constellation of water
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bodies one hundred miles northwest of the Enide Plateau is
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one of the few places where this colossal repository reaches
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the surface. Enides Guelta's small reservoirs concealed within its rock
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formations are another. When we visited Ourshai, the canyon was deserted,
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aside from a heavy set man and a pair of
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teenage boys bathing in the murky water. The dramedaries that
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congregate here during the dry periods between October and June
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were nowhere to be seen, dispersed by now by the
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renewed availability of water elsewhere. But the Guelta's plentitude was
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still evident in the abundance of scat and footprints covering
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the sand bags. Guemona pointed to the clawed prints of
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the nile crocodiles that were lurking somewhere unseen. As we
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headed east towards the plateau's remotest reaches, the desert felt
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protean acacias grew with vigorous displayed canopies. Chevrons of migrating
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birds passed overhead, and gazelles scampered over distant ridge lines,
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hicking up trails of dust. Swifts gorged on insects and
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fat toads chorused around ephemeral ponds. In one wody, we
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found the tendrils of a newborn river clawing northward, turbid
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with alluvium, pursued by watering camel herds. In places across
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acres of what just one week before was nothing but sand,
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new grass chutes were germinating by the million. To Guemona
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Endy is foremost a museum. We stopped, often, usually at
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the archaeologist's bidding, and he would lead us into the
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outcroppings to seek out the rock art he had been
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documenting for the last three years. He and his genial deputy,
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Mohammat Ahmat Humar, often spent whole weeks exploring remote maces,
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scouring niches and overhangs for neolithic artworks, and recording their
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discoveries on a proprietary database. During our time in the reserve,
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we lived as they did on these regular forays, sleeping
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in the open, then waking before sunrise, brushing off the
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night blown sand to go again. Wuimona and Umar's list
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of archaeological sites is already expansive one thousand, nine hundred
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and twenty one and counting deep among these rock forests,
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they and their team have uncovered nomadic rock shelters, sprawling necropolises,
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and ancient metallurgical workshops of indeterminate age, but around sixty
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percent of the finds are petroglyphs, archaic representations of the
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herding culture that remains the predominant lifestyle throughout the southern
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Sahara and the Sahel. The tableau we saw on that
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first dawn, which Gromona had discovered in June twenty twenty two,
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was of a special order, but there were thousands more
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scattered across the reserve, paintings of pastoral scenes, horned warriors
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with shields and spears, etchings of rotund female figures decorated
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with chevron markings, cryptic geometric patterns. One hudo, near the
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outpost of Morti, had the feel of an art gallery
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in which every rock exposure was an antique canvas. Among
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the artworks were several cattle etchings close to full size,
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and these showed the cows decorated with stippled and dappled
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motifs painstakingly engraved with the beveled stone. Guemona believes that
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the sheer diversity of the depictions, which spanned the social
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transitions from hunting and gathering to pastoralism to nobadism, suggest
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an unbroken chain of human habitation dating back at least
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nine millennia. In Chad, this heritage remains virtually unknown, he
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told me before we started this work. It was rare
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to read anything about energy outside specialist scientific journals. Several
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times a year, Groemona led field trips for local children,
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where he would part the natural and cultural significance of
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the land they call home. After two days, we came
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across a group of elders gathered in an acacia's shade,
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a few younger men in desert fatigues. Members of an
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African Park's community outreach program were holding forth in front
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of a flip chart. Since the organization took over the
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management of Enity, its personnel, most of them Chattyan Nationals,
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had begun to roll out the conservation strategy that it
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employs throughout Africa, where its stewards some of the continent's
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most precious and embattled biospheres. The aim is not just
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to protect, but also to restore. Part of this effort
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has involved re introducing wild animals that had diminished or
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disappeared in the face of human encroachment. Several at axes,
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critically endangered Saharan antelopes with long corkscrew horns, had recently
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been flown in from Abu Dhabi. Outside Fada, a team
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of biologists was running a breeding program for red necked
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ostriches and endy as. In any living reserve, success depends
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on the co operation of their resident population. Today's conclave
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was arranged to discuss ways of minimizing contact and grazing
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competition between domesticated animals and endemic wildlife. After the meeting,
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as the crowd dispersed, idris Mina Luki lank and high
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cheek boned, and a sky blue kuptani an ensemble and
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white Kadumul turban lingered behind to talk. Luki sixty seven,
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knew about the Sahara's greener past. According to his folk chronology,
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the elephants and giraffes memorialized in nearby glyphs existed in
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the time before my great great grandparents. But Luki still
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fondly recalled relic species from his childhood when he would
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occasionally glimpse antelopes and cheetahs on his family's ancestral lands.
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All that changed with the onset of a multi year
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drought in the nineteen seventies, when many of the region's
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larger animals died off or were poached for bush meat.
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The huge dead trees scattered hereabouts, their trunks splintered and
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bleached ivory, were the detritus of years of faltering rains.
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Even as the Saharan climate follows long term trends, its
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seasonal rains continued to fluctuate on a more human time frame.
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In Enindy, climate, catastrophe is not only a living memory,
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but also an ever present menace. The efforts to reintroduce
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some of Enidy's lost phantoms symbolize a welcome sense of regeneration. However,
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fragile Lukie told me most of the younger people only
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knew these animals from family stories. He said his grandchildren
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were excited to see them return. As we continued into
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the reserve's western quadrant, the rock formations began to rise
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in number and scale. Crags that appeared from a distance
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to be solid monoliths disintegrated on approach, resolving into spires,
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fungal sculptures, voluminous grottoes, most of them unremarked upon and unnamed. Soon,
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Endy's rock art receded behind the sheer spectacle of the geography,
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all of it a testament to what Martin Williams characterized
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as a constant tug of war between flowing water and
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wind blown sand. For scientists seeking to establish the contours
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of that geological tangle, challenges abound. Political volatility has long
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hindered access for land based scientific studies. Even today, Chads
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neighbors Niger, Libya, and Sudan are each in the grips
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of civil unrest or violent insurgency. Another part of the
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problem is morphological Sandstone is the compressed state of a
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substance that is otherwise granular and fluid, even as it
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solidifies into stone. Sand is less likely than other sedimentary
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rocks such as shale and limestone to preserve the fossils
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and geological layers that help reveal when past humid periods
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have occurred. In search of a coherent timeline, geologists have
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had to look farther afield to archives of dust and
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vegetation that have blown off the Saharan land mass and
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accumulated in terrestrial water bodies and on the ocean floor.
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In the past few decades. A slew of such evidence
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as indicated that the most recent nahp ending roughly five thousand,
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five hundred years ago, was merely the latest in a
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long term cycle. One widely cited study that analyzed more
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than one thousand, two hundred sediment samples taken from the lakes,
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wetlands and rivers across North Africa proposed that there have
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been two hundred and thirty humid periods over the last
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eight million years. The timing and amplitude of these recurrences
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is determined by a variety of factors, including ocean current
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circulation and the onset of polar ice ages, but most
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researchers agree that the prime driver is orbital precession, one
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of three cycles that govern the Earth's rotational orientation as
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it passes around the Sun. Edward Armstrong, a climate scientist
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at Finland's University of Helsinki, suggested to me that precession
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can be visualized as the motion of a spinning top,
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not its rotation or month migration across a surface, but
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the slight axis wobble at its apex. Armstrong is part
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of an international team of researchers engaged in a long
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term collaboration between the universities of Helsinki and Bristol in
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England to identify past nahps and their influence on human
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evolution and dispersal. Central to the study has been a
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climate model tuned or paleo conditioned to reflect various atmospheric
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parameters over the last eight hundred thousand years, including the
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Earth's orbital positioning, its polar ice sheet coverage, and the
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corresponding historic carbon dioxide levels. The resulting simulation, the first
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to dynamically model the greening cycle, suggests that the phenomenon
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is triggered by small changes in seasonal solar radiation. This
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thermal uptick is then reinforced by feedback loops as burgeoning
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vegetation suppresses the amount of sunlight reflected back from the
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Earth's surface and accelerating rates of evaporation and transporation increase
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atmospheric moisture. It all begins with a slight orbital perturbation
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and a slight intensification of the monsoon, which then amplifies
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and amplifies and amplifies. Armstrong told me the next stage
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of the Bristol Helsinki study is to illuminate what role
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humid periods may have played in creating verdant corridors to
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facilitate the migration of early humans throughout North Africa and beyond.
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The Sahara is a gait, said Mika Talavera, a scholar
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of hominine environments at the University of Helsinki who leads
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the multidisciplinary project. We can be certain that n A
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h p s were crucial for out of Africa range
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expansions and the exchange of genes and ideas, but the
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precise dynamics remained something of a mystery. On our penultimate
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evening in the reserve, we camped by a lone acacia
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miles from any sign of human habitation. Behind the camp
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was a dune, and after dinner I walked up to
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the crest. On the far side, a dust bowl stretched
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to the horizon. I tried to imagine the scene during
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the deep greening of the iman humid phase more than
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one hundred thousand years ago, with the insects rising in
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clouds and the bird life swollen by several degrees of magnitude.
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In the valley, antelope and other ungulates gathering to drink
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at year round water holes, and great elephant herds crashing
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through stands of broad leaf woodland, and beside me on
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this ridge, swathed in waist high grasses, a band of
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hunter gatherers pausing to survey a totally different biome. Present
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day descriptions of entity as a garden of Eden may
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be more apt than we know. In two thousand one,
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a partial skull was unearthed in the Jirab Desert, three
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hundred miles west of here. The discovery of Sohilanthropus chadensis,
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nicknamed Tumai and believed by some to be the oldest
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known hominin, led to speculation that our distant ancestors have
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inhabited this region for seven million years. In the face
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of ongoing academic rancor and dispute, its discoverers have claimed
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that the Sahara, and not East Africa's Rift Valley, could
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be the true cradle of humankind. Fifty miles south of Fada,
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under midday sun, Ghemona knelt down to pick up a
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glossy plaque object from the sand. It was a charred
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mass of iron, its lump and residue mixed in with
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shards of charcoal that had been used to smell it.
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Evidence Guamona explained of a metallurgical site that was perhaps
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four hundred years old. He paused to enter the GPS
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coordinates in the database on his phone. It went down
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as the forty sixth site in the immediate environs. To
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some extent, Wamona and Umar's campaign to catalog Niede's archaeological
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treasures is a race against time. Occasionally they sought to
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show me petroglyphs, only to find that in the months
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since they had recorded their location, they had disappeared. Perhaps
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the patinas had collapsed, or perhaps the paint had faded
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to such an extent as to be undetectable. Guamona couldn't
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be sure. Soon after our trip he hosted a visit
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from Frederic to Quesnoi, a French expert in Saharan rock art,
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who made three D digital renderings of some of Nidee's
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most known notable petroglyphs for posterity. Still, there was so
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much left to do. Wimona reckoned that he had reconnoitered
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around thirty percent of the reserve, but hundreds of square
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miles remained to survey. Last year, he left African Parks
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to take a job with Chad's National Research and Development
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Center passing the mantel to Umar his protegee. Umar's mission
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is to push further probing unexplored regions and excavating at
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sites already known to have exceptional value. Umar told me,
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I am convinced that the reserve still holds many secrets
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that could enrich and even transform our understanding of ancient
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societies in this desert environment. This concludes readings from the
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Smithsonian Magazine for to day. Your reader has been Rebecca Shore.
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Thank you for listening, and have a great j