Was North Africa the Launch Pad for Modern Human Migrations?

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Was North Africa The Launch Pad on January 7, 2011 For Modern Human Migrations?

A growing number of researchers suspect that long-neglected North sophisticated tools and ornaments of famed www.sciencemag.org South African sites such as Blombos Cave Africa was the original home of the modern humans who ﬁ rst trekked (Science, 16 April 2004, p. 369). Few sci- out of the continent entists thought that much of evolutionary signiﬁ cance had gone on in North Africa, LAST YEAR, ARCHAEOLOGISTS EXCAVATING onized the rest of the world come from? “It’s or that the region’s big-toothed, somewhat at the Grotte des Contrebandiers (Smug- a very exciting specimen,” says anthropolo- archaic-looking hominins might be closely

gler’s Cave) on Morocco’s Atlantic coast gist Jean-Jacques Hublin of the Max Planck related to the ancestors of many living peo- Downloaded from unearthed a rare prize: the skull and partial Institute for Evolutionary Anthropology in ple. “We’ve left North Africa off the map skeleton of a 7- or 8-year-old child. The fos- Leipzig, Germany. for so long, and now it deserves to be there,” sils, dated to 108,000 years ago, appear to For Hublin, who was born in Algeria, says paleoanthropologist Chris Stringer of belong to an early member of our species, the Contrebandiers child adds to grow- the Natural History Museum in London. although study of them has just begun. ing evidence that North Africa was likely Indeed, a fl urry of research has now put But one feature stands out already: “It a major source of the modern humans who the region fi rmly on the map of human evo- has huge teeth,” says Harold fi rst left humanity’s homeland lution. Thanks to new excavations and more Dibble of the University of and spread into Europe and accurate dating, North Africa now boasts Pennsylvania, co-leader of Asia as early as 130,000 years unequivocal signs of modern human behav- the dig team. That’s a feature ago. “If you look at a map and ior as early as anywhere else in the world, the child shares not only with think how modern humans including South Africa. Climate reconstruc- other hominin fossils found would have moved out, you tions and fossil studies now suggest that across North Africa but also would logically look at North the region was more hospitable during key with some of the fi rst modern Africa,” he says. periods than once thought. The data suggest humans to leave Africa. And Nevertheless, until very that the Sahara Desert was a land of lakes so the new fossil may contain recently, most researchers and rivers about 130,000 years ago, when clues to an enduring mystery studying the origins of Homo moderns fi rst left Africa for sites in what is in human origins research: sapiens looked elsewhere, today Israel. And new studies of hominin Just where in Africa did the Old youngster. This fossil focusing instead on the fos- fossils suggest some strong resemblances—

modern humans who ﬁ rst col- child had big teeth. sils of East Africa and the and possible evolutionary connections— CREDITS: HAROLD DIBBLE

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Digging for our roots. Modern humans Some of these early migrants may have el Ater in eastern Algeria, the tools include occupied many North African sites, like gone east, across the Red Sea and along the triangular objects that some suggested were this one at Contrebandiers, Morocco. southern coast of Arabia. But the earliest used as arrowheads or spear points (see known modern human fossils outside Africa photo, p. 23). At least 100 Aterian sites have between North African specimens suggest a northern route, perhaps through now been uncovered across North Africa, and fossils representing migrations the Nile Valley: Modern human skulls and including in what is now the Sahara Desert. out of Africa between 130,000 and other bones discovered in the early 20th cen- But when archaeologists radiocarbon-dated 40,000 years ago. tury in the Skhul and Qafzeh caves in Israel these sites, they tended to throw out any This barrage of new evidence are now dated to between 100,000 results older than 40,000 years, is reported in recent papers and in and 130,000 years ago, although Online says archaeologist Elena Garcea two new edited volumes (see Addi- researchers debate whether these of the University of Cassino in tional Reading below). Human evo- early colonizers traveled any far- sciencemag.org Italy, because such dates were at Podcast interview lution researchers working in other ther at that early date (Science, with author the limit of the radiocarbon tech- parts of Africa are taking notice. The 9 October 2009, p. 224). Michael Balter. nique and considered unreliable new studies are “long overdue,” says Despite this early connection (Science, 15 September 2006, anthropologist Stanley Ambrose of to the Middle East, not so long ago most p. 1560). “In the past, the Aterian was the University of Illinois, Urbana- experts thought that modern humans occu- thought to be relatively late and not terribly Champaign, who works in East pied North Africa itself relatively late. The exciting, … a sideline or a dead end,” says Africa. They “show that North Afri- earliest known modern human fossils were archaeologist Nick Barton of the University cans may be responsible” for both from East Africa: Skulls and bones found of Oxford in the United Kingdom. early and later H. sapiens migra- near Kenya’s Omo River by Richard Leakey By 1998, however, it began to look like tions out of Africa. Adds archaeolo- and others are now dated to 195,000 years archaeologists might be throwing away the gist Curtis Marean of Arizona State ago, and skulls found at Herto in Ethiopia University, Tempe, “If I were not clock in at about 160,000 years old. Then,

working in South Africa, I would in recent years, Hublin, Stringer, and oth- on January 7, 2011 probably be in North Africa.” ers convinced most anthropologists that a But a key question, Marean and 160,000-year-old skull from Jebel Irhoud other researchers say, is whether in Morocco was that of an archaic modern modern humans in North Africa human and not a Neandertal, as previously were foremost among the migrants thought. But that skull was considered an that eventually left Africa, or anomaly, perhaps representing a population whether those populations repre- that got trapped north of the Sahara and then sented an evolutionary cul-de-sac died out. that was left behind when humans from other This picture of North African hominins www.sciencemag.org parts of the continent began moving into as Johnny-come-latelies was reinforced by Asia and Europe. The evidence that North assumptions about the dates of characteris- Africa was a population pool for migrations tic stone tools in the region. Called Aterian to Eurasia is not yet conclusive, says anthro- after their discovery in 1917 at the site of Bir pologist Gerhard Weber of the University of Vienna. Marean is also cautious for now O pioneers. Early modern humans like this one

but says the new work should provide “some from Dar es-Soltan (computer reconstruction, Downloaded from good answers in the future.” right) may have spread across North Africa and into Eurasia. Old tools, new dates Given what researchers already know North African hominin sites about modern human evolution, the long neglect of North Africa might seem sur- Pes¸tera cu Oase prising. Most anthropologists think that our species, H. sapiens, ﬁ rst evolved in sub- Mugharet el ‘Aliya Dar es-Soltan Grotte des Pigeons Saharan Africa about 200,000 years El Mnasra Bir el Ater Contrebandiers Grotte du Rhafas Haua Fteah Skhul ago and began migrating out of Jebel Gharbi Africa between 70,000 and Jebel Irhoud Ifri n’Ammar Qafzeh 50,000 years ago, eventually Uan Afuda Nazlet Khater Uan Tabu r colonizing the globe. And ive le R although the expansion has Nil often been considered a single migration, many researchers are beginning to suspect that moderns left Africa in two or more Aterian sites Non-Aterian sites CREDIT: RECONSTRUCTION BY HUBLIN AND NEUBAUER CREDIT: waves.

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wrong dates. That year, researchers used the iers to determine whether is entirely plausible,” says new techniques of optically stimulated lumi- they, too, were used as per- Sarah Tishkoff of the Uni- nescence (OSL) and thermoluminescence sonal ornaments. versity of Pennsylvania. (TL) to date Aterian sites in Libya back to All this implies that the “We can only study popu- 70,000 years, and soon afterward similar Aterian was not a sideshow lations present today, and dates using these and other methods were but a “[cultural] package their present-day distri- found at other Aterian sites in the region. that may be linked with bution probably doesn’t During the past 2 years, the dates have the emergence of mod- reflect where they origi- gotten even older. In 2009, Barton and ern human behavior,” says nated from tens of thou- Abdeljalil Bouzouggar of the National Insti- Barton. That’s not direct sands of years ago.” tute of Archaeological and Heritage Sci- evidence that the Aterians ences in Rabat reported OSL dates of at were the source of out- Rain over the Sahara least 110,000 years from the Aterian site of-Africa migrations, but Facing the past. The Max Planck’s Today, no sensible hom- of Dar es-Soltan in Morocco; and in a new it suggests that they met Jean-Jacques Hublin sees similari- inin would think of trying volume edited by Garcea, the team reports an important prerequi- ties between the Aterians and the to cross the Sahara Desert. similarly old dates from three other Moroc- site: Rather than being a ﬁ rst modern humans to leave Africa. This vast landscape of sand can caves. Then in September, TL dates of small, isolated population dunes, rocky plains, and about 145,000 years were reported for Ifri unlikely to go on the move, they apparently plateaus covers 5 million square kilome- n’Ammar in Morocco. “The Aterian goes were part of extensive social networks that ters from the Atlantic Ocean in the west to back at least 145,000 years,” Stringer says. used ornaments to signal the identities of the Red Sea in the east. The Sahara overall “That’s an incredible length of time.” different groups that were in contact with receives less than 8 centimeters of rain each Those early dates are coupled with a one another, perhaps across long distances year, and the driest parts might not see rain growing realization that the Aterians were (Science, 9 April, p. 164). for years on end. But during key periods in

ern humans in other parts of Africa. In research, which has suggested that the sources suggest, at least parts of the Sahara on January 7, 2011 addition to their skillfully made tools, they humans who dispersed to Europe, Asia, and featured lakes, rivers, and trees. PNAS made personal ornaments—a key sign of Australia by 50,000 years ago originated in Scientists are now working to correlate modern, symbolic behavior—from shell sub-Saharan Africa (Science, 1 May 2009, the cyclical greening of the Sahara with beads 82,000 years ago at Morocco’s Grotte p. 575). But Hublin argues that such stud- archaeological signs of human occupa- des Pigeons (Pigeon Cave). That’s some- ies, which are based on the genetic diver- tions. For example, satellite radar imaging what earlier than when the same genus of sity of humans today, might not capture past has revealed a system of more than 800 kilo- shells, Nassarius, was used to make beads patterns. For example, some of the Aterians meters of channels, some more than 5 kilo- at Blombos Cave thousands of kilometers in the Sahara area—along with their meters wide, buried under the eastern Sahara away in South Africa 75,000 years ago. genes—may have moved east or south when sands. A 2008 study of 120,000-year-old www.sciencemag.org Nassarius beads show up at Qafzeh in Israel the Sahara became hotter and drier after snail shells suggests that these are river cor- even earlier, at least 100,000 years ago 60,000 years ago. ridors, which could have supported human (Science, 23 June 2006, p. 1785). Research- Leading geneticists support the idea that migrations (http://scim.ag/wetsahara). ers are now studying 108,000-year-old per- some of the populations that live south of the And trees increased markedly 120,000 and forated Nassarius shells from Contreband- Sahara today may have Aterian roots. “This 50,000 years ago, according to work published last year on isotopes from plant

leaves in a marine core off the coast of Downloaded from European connection? Some features, northwest Africa. such as the molars, of these 40,000-year- Other recent work suggests that old specimens from Romania resemble those of earlier North African hominins. Libya, Chad, Tunisia, and Egypt were dotted with huge “megalakes” about

120,000 years ago; about 10% of Libya ET AL. , E. TRINKAUS U.S.A.; SCIENCES, OF ACADEMY 2007 NATIONAL 2007) © 104 JANUARY (23 might have been underwater around that time, concludes geographer Nick Drake PNAS of King’s College London. These wet phases lasted for thousands of years. “One of the wettest times was around 120,000 to 130,000 years ago,” says geologist Jennifer Smith of Washington University in St. Louis (WUSTL). That’s about when modern humans first left Africa and are found in the Israeli caves of Skhul and Qafzeh. A wet Sahara between 100,000 and 130,000 years ago may also help explain how shell bead ornaments ended up in

both North and South Africa some tens of CREDITS (TOP TO BOTTOM): PETER ENDIG; H. ROUGIER ET AL. ,

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“We’ve left North Africa off the map for so long, and now it deserves to be there.” —CHRIS STRINGER, THE NATURAL HISTORY MUSEUM IN LONDON

thousands of years later, says Hublin, if far- more than 50 hominin teeth from Aterian The big teeth “certainly potentially link ﬂ ung populations were in touch across the sites with more than 200 teeth from Nean- the Aterians with Oase,” says the Natu- continent. “If you look before 100,000 years dertals as well as modern humans from sev- ral History Museum’s Stringer, making the ago, North Africa was very much connected eral continents. The Aterian teeth, which Aterians candidates for the ancestors of later to the rest of Africa,” he says, adding that fos- have very large molars and a distinctive pat- Europeans. sils of sub-Saharan animals such as rhinos, tern of cusps, clustered most closely with But to nail down those evolutionary rela- giraffes, and hippos have been found at North those from Qafzeh and Skhul. And they tionships, Stringer says, “we need good sam- African sites. “We had a network of early also strikingly resembled those of the earli- ples from northeast Africa,” because most modern populations all over Africa, some- est known modern humans in Europe: a cra- Aterian fossils are from Morocco in north- times connected and sometimes separated.” nium and mandible, dated to about 40,000 west Africa. “The people in Morocco could Yet despite some evidence, for example years ago, from the site of Peştera cu Oase have been marginal.” He adds that the early from the tree study, that parts of the Sahara in Romania. Oase skull from Romania might not have been continued to experience wet periods as closely related to the modern humans late as 50,000 years ago, the climate who later colonized the rest of western data suggest that the Sahara had greatly Europe and left the famed Aurignacian expanded by that time. Indeed, Garcea and Gravettian cultures; those cultures says, no Aterian sites are found in the could represent a later wave of more Sahara after about 60,000 years ago, gracile, smaller-toothed H. sapiens.

although the Aterian continues until Other researchers remain even on January 7, 2011 about 40,000 years ago all along Afri- more skeptical. Paleoanthropolo- ca’s northern Mediterranean coast. gist Erik Trinkaus of WUSTL, who has extensively studied the Oase fos- Bones tell a new tale sils and thinks they represent admix- Did the Aterians themselves die out, or ture between Neandertals and moderns, did they live on to join the exodus out of rejects any close connection between Africa? The bones they left behind offer Signs of sophistication. The Aterians made personal orna- them and the Aterians. He sees “some some tantalizing clues. The Aterians ments (above) and advanced stone tools (below). superficial resemblances in terms of were kind to human evolution research- large molars” between Oase and Aterian www.sciencemag.org ers: They left not only ample artifacts specimens but few other similarities. In but also one of Africa’s best collec- fact, he thinks the Aterians weren’t fully tions of modern human fossils. Now modern humans but “archaics” living in new analyses of Aterian faces and teeth an isolated corner of Africa who were suggest that at key times, populations an evolutionary dead end. North Africa across North Africa and the Middle East was “just another cul-de-sac,” he says.

were “relatively closely related,” says But that view of the Aterians is Downloaded from paleoanthropologist Katerina Harvati of rejected by many other anthropologists. the University of Tübingen in Germany. The emerging evidence, Hublin and oth- For example, in a paper in an upcom- ers say, suggests that at the critical time, ing volume co-edited by Hublin, Har- prehistoric North Africans enjoyed the vati and Hublin compared an Aterian right climate, engaged in the right sym- skull with those of other early hominins. bolic behavior, and possessed the right They analyzed the facial features of a par- Earlier, other researchers had also anatomy to be leading candidates for the tial skull found at Dar es-Soltan—now dated found resemblances—such as the robust ancestors of at least some of the H. sapiens to about 80,000 years ago—using the three- shape of the lower jaw and forward- who left Africa. So for a growing number of dimensional coordinates of 19 facial land- facing cheekbones—between Oase and a researchers, North Africa is a very promis- marks. The Dar es-Soltan skull most closely 40,000-year-old skull from the site of Nazlet ing place to look. Says Dibble: “We have resembled two 100,000-year-old skulls from Khater in Egypt, providing another potential exactly the kind of thing everyone has been Qafzeh as well as the 160,000-year-old Jebel North African link to the earliest Europeans. searching for, right here.” –MICHAEL BALTER Irhoud skull; it showed much less affin- “There are indeed some afﬁ nities between ity with Neandertal skulls or with younger Oase and Nazlet Khater,” says anthro- Additional Reading: modern humans from any continent. pologist Hélène Rougier of California State E. A. A. Garcea, Ed., South-Eastern Mediterranean Peo- In a second paper, Hublin, along with University, Northridge, who worked on ples Between 130,000 and 10,000 Years Ago (Oxbow dental experts Shara Bailey of New York some of these studies, although she notes Books, 2010). University and Tanya Smith of Harvard that the contemporaneous skulls differ in J.-J. Hublin and S. McPherron, Eds., Modern Origins:

CREDITS (TOP TO BOTTOM): IAN R. CARTWRIGHT ©INSTITUTECREDITS TO BOTTOM): IAN R. (TOP CARTWRIGHT OF ARCHAEOLOGY/UNIVERSITY CECCACCI OF OXFORD; ROBERTO University, compared the size and shape of other traits. A North African Perspective (Springer, in press).

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