Libya Before the Sahara
IIHER Occasional Paper #1
International Institute for Human Evolutionary Research Hominem sapientia pro Hominibus Libya Before the Sahara: The Vanished World of the Eo Sahabi Valley Noel T. Boaz Art by Antonio Varelas Libya was once a lush forested savanna with prolific grasslands flanking one of Africa's great rivers. Encroaching Saharan sands and mountain-building that cut off the flow of water wiped out a diverse fauna and flora. Somehow hominids survived. Occasional Papers, No. 1 (2009) Cover photograph: AsSahabi Locality P28 and the "petrified forest" fronting Garet Makada ("Elephant Hill"), west of Sebkhat alQunnayyin, Libya. Published by the International Institute for Human Evolutionary Research Integrative Centers for Science and Medicine 2565 Siskiyou Boulevard, Suite 4/1L Ashland, OR 97520, U.S.A. http://integrativemedsci.org Shell Exploration and Production Libya GmbH is a major sponsor of the East Libya Neogene Research Project and provided financial support for this publication. � 2009 International Institute for Human Evolutionary Research ISBN 9780964424838 Today when one drives south from the Libyan coast into the Sahara Desert, it is hard to imagine what the scenery might have been like before sand blanketed the landscape. Today plants and animals are sparse. Except for the palms at isolated oases, there are no trees. The animals that one sees, such as camels, goats, and the occasional dog, are not native to the desert but are domesticated species brought in by humans. In fact, over 90% of Libya's land is desert. But it was not always like this. Once a great river flowed through Libya � like the Nile in Egypt, the Niger or the Congo in western Africa, or the Zambezi in southern Africa. It is called the EoSahabi River. The river was surrounded by many wild animals. Chat tering birds, monkeys clambering in trees, and hippos basking in the sun lived along the river. On the open plains extending inland, there were herds of antelopes and threetoed horses, hyenas, sabertooth cats, pigs, and many other species. Our scientific teams have discovered the fossilized bones and teeth of all these animals in this nowvanished world. Where did all the water in the ancient river come from and where did it go? What happened to the many animals and plants that lived in Libya millions of years ago? The site of AsSahabi in North Central Libya, one of Africa's great fossil sites, has given us a window into this very different world and has enabled scientists to answer many of these questions. Geological and paleontological research has been going on at AsSahabi since the mid1970's and continues today. Exhibits on the exciting fossil discoveries from this site can be seen in the Earth Science Museum at Garyounis University in Benghazi, where our East Libya Neogene Research Project is based, and at the National Museum of Libya in the Sarayy alHamra in Tripoli. The Site of AsSahabi The site of AsSahabi first became known not as a window to the past, but for window panes. When Libya was a part of the Roman Empire, around 100 B.C., the site was an important source of large crystals of gypsum or selenite, used for constructing window panes in Roman buildings. We now know that this gypsum was deposited in an ancient lagoon in an embayment of the Mediterranean Sea. A fort near a small oasis was built by the Romans to guard the gypsum mining operation from marauding Berbers. After the Romans left Libya the fort of "Qasr asSahabi" was taken over and enlarged by Byzantine, Turkish, and Italian armies. It was largely destroyed during the Second World War but the outlines of its walls are still to be seen today. Italian soldiers stationed at Qasr asSahabi were the first to find fossils in the region. They informed famed Italian geologist Ardito Desio, the same man who first discovered oil in Libya. Desio recruited a young paleontologist named Carlo Petrocchi whose discoveries in the 1930's would make AsSahabi the most LIBYA AsSahabi The fossil site of AsSahabi is located in North Central Libya at the northern edge of the Sahara Desert. International Institute for Human Evolutionary Research Occasional Paper 1 Left. Excavation and removal of the skeleton of the fourtusked elephant, Stegotetrabelodon syrticus, at AsSahabi in 1934, as depicted by Carlo Petrocchi in 1951. Below. The habitat of the riverine forest and river edge. The AsSahabi sixforetoothed hippo (Hexaprotodon sahabiensis) is in the left foreground and two AsSahabi fourtusked elephants (Stegotetrabelodon syrticus) are in the background. The rare AsSahabi colobine monkey is in the right foreground while a group of the more common ma caquelike cercopithecine monkeys (Parapapio sp.) is seen in the left middle ground, lounging under a sau sage tree (Kigelia). One of two species of bear at Sa habi (Agriotherium africanum), Africa's earliest, am bles through the left background. A darter (above cen ter) and eagle (above right) fly above the river looking for fish. 2 Boaz Libya Before the Sahara famous Libyan fossil site. Petrocchi's first major discovery was his best � a virtually complete skeleton of a previously unknown elephant. Incredibly, this species had not two tusks, but four! It was named Stegotetrabelodon syrticus, meaning "four tusker from Sirt" [the Libyan gulf]. Excavating, hardening with glue and plaster, and crating the fossil skeleton for shipment was a huge undertaking, but when it arrived by truck in Tripoli it created a sensation. The colonial Italian governorgeneral of Libya established in Tripoli an entire museum � the Libyan Museum of Natural History � with the As Sahabi elephant fossil as its centerpiece. This museum only survived a few years but it was the forerunner of today's Libyan National Museum. The famous Stegotetrabelodon is still there in the old museum building in Sarayy alHamra. Over the years it has been featured on two Libyan postage stamps and is considered by those who remember him as Libya's "national fossil." This unique witness of Libya's ancient past is awaiting a new and better home in the national museum where Libyans and tourists alike can visit him again. The Underwater Habitats: Freshwater and Saltwater As amazing as it seems to a casual visitor to the AsSahabi desert today, all the rock and blowing sand were originally brought there by water. Wind has sculpted the rocks and moved the sand around but it was the ancient The freshwater habitat in the EoSahabi River. A large widehead catfish (Clarotes laticeps) and a school of bichirs (Polypterus) swim near the river bottom. A group of crucifix catfish (Arias) swims in the middle foreground. A spotted sqeaker catfish (Synodontis), catfish (Clarias), and Nile perch (Lates nilotica) swim in the left middle ground. The longsnouted crocodilian Euthecodon has just captured a Nile perch. Two iniid river dolphins swim in the left background, while in the right background sparid sea bream and the bottlenosed dolphin Lagenorhynchus swim out seaward toward estuarine waters. 3 International Institute for Human Evolutionary Research Occasional Paper 1 EoSahabi River and its adjoining lagoons and estuaries of the Mediterranean Sea that laid down the sediments of what we now call the Sahabi Formation. The animals which lived in those waters were abundantly preserved as fossils. These animals were primarily fish, and most of them were species that today live in freshwater. The underwater freshwater riverine habitat preserved at AsSahabi is what fossil workers call the "proximal" (nearby) burial environment. The fish fossils buried at As Sahabi were the native species that lived there. The sedimentary rocks preserving the fossils represent the same environment in which the fish lived when they were alive. We call such a collection of bones "autochthonous" � their habitat during life and their burial environment were one and the same. The fish fossils tell us much about the Eo Sahabi River. The sizes of the preserved fish The saltwater underwater habitat in AsSahabi lagoonal embayment. A Crocodilus checchii preys on a sea turtle (Trionyx triunguis) in the left foreground while great white sharks (Carcharodon megalo don) swoop down on a group of sea cows (Metaxytherium serresii). Above, a group of geese flies out over the water. 4 Boaz Libya Before the Sahara bones are generally large, indicating that the fish were big and were living in a major river with a lot of food resources and a lot of room for them to live to old age. Just from the evidence of its fish fauna, we know that the Eo Sahabi was a large and perennially flowing river. The species of fossil fish at AsSahabi are also found today in Lake Chad, the Nile River to the east, the Congo River to the south, and the Niger River to the southwest. Usually rivers share species because they were connected in the past. AsSahabi shares the most species with Lake Chad, indicating that this connection was the closest and most important. Even without physical connections though fish can be transported from one river basin to another by birds. Fisheating birds, such as eagles and darters, both known as fossils at As Sahabi, may carry fish through the sky for kilometers and may drop them by accident in a different river drainage system. Wading birds, such as storks, also known as fossils at AsSahabi, may transport fish eggs from mud on their feet from one river system to another. The percentages of fish species shared between the EoSahabi and the other great regional African rivers decrease from the Nile to the Congo to the Niger, correlating with each river's geographic distance away. It is most likely that bird transport of these fish species accounts for this pattern of distribution. Outside of the EoSahabi River Lake Chad system, the Nile River is the closest geographically and shares the most fish species. Other, airbreathing, animals shared the Eo Sahabi freshwater habitat with fish. A species of extinct longsnouted crocodile, the euthecodon, had specialized jaws for catching fish. It is also found at fossil sites in the Nile and Congo River drainages. Two fisheating aquatic mammals swam among the fish. A species of river dolphin, now extinct in African rivers, and a fossil harbor seal, now extinct in 5 the Mediterranean Basin, lived in the Eo Sahabi River and estuary. As the EoSahabi River wound its way to the sea it widened out into embayments, estuaries, and lagoons. These bodies of water had a higher salt content than the river itself and supported a community of animals different from the freshwater river itself. Fossils from this habitat are found preserved in different sedimentary rocks � white strata of dolomite deposited under lagoonal conditions. Some small marine fish such as sea bream (sparids) are found here but they are rarer than are the fish in the riverine deposits. The most common fish in the lagoons were big sharks, in fact the biggest species of all, the great white shark (Carcharodon megalodon). The paleontological evidence at AsSahabi shows great white shark teeth among the abundant skeletal remains of sea cows (Metaxytherium serresii), whose distinctive puffy ribs show the deep gashes of shark attacks. The vegetarian sea cows grazed at As Sahabi on extensive beds of sea grass (Posidionia) that grew around the margins of the Mediterranean Basin. The same sea cows are found in similaraged fossil deposits in southern France. A unique fossil crocodile (Crocodilus checchii) that was first discovered at As Sahabi had a distinctive raised bump on its snout. Living crocodiles in Cuba have a similar bump that houses a gland that secretes salt, an adaptation that allows this species to range into salt water. Fossil remains of the AsSahabi sea turtle (Trionyx triunguis) show the unmistakable bite marks of crocodiles and were probably a favorite food. Another species of dolphin (Lagenorhynchus) discovered at AsSahabi is related to living dolphins who are adapted to marine coastal habitats worldwide but went extinct when the Mediterranean dried up after AsSahabi times, about 5 million years ago. International Institute for Human Evolutionary Research Occasional Paper 1 A Contrast of Terrestrial Habitats-- Swamps and Deserts The many fish in the underwater habitat of the EoSahabi River would have been used to seeing the feet of the airbreathing animals who shared their environment. These were hippos, fourtusked and shoveltusked probocideans, and the occasional antelopes, pigs, carnivores, and other obligate land animals that waded in. But the most common airbreathing animals in the aquatic e n v i r o n m e n t w e r e u n d o u b t e d l y anthracotheres (literally "black beasts" because their first fossils were found in European coal deposits). Anthracotheres were swampforestdwelling, piglike animals widespread in the fossil record of Eurasia and Africa and found in sites in which environments were wet, warm, forested, and swampy. Interestingly, anthracotheres were A group of anthracotheres (Libycosaurus petrocchii) feed on lush swamp grasses near the wa ter's edge while a harbor seal swims by into the EoSahabi estuary. In the middle ground an other denizen of the Sahabi swamps, the "shoveltusker" proboscidean (Amebelodon cyrenaicus) forages. In the background can be seen the sabertooth Amphimachairodus aff. kabir. 6 Boaz Libya Before the Sahara Over half of the small mammal fauna from Sahabi is the aridadapted gerbil Abud habia yardangi, providing a stark contrast with the wet adapted anthracotheres. A ground squirrel (Atlantoxerus getulus) looks out from its perch on a rock outcrop. close companions to the ancient apes that are found in the tropical forest fossil sites of Africa and Asia predating AsSahabi, suggesting that their habitats shared significant ecological similarties. The anthracothere Libycosaurus is the most abundant large mammal at As Sahabi even though the impressive four tusked elephant Stegotetrabelodon is the most wellknown. Despite their abundance at AsSahabi, anthracotheres were a dying breed. AsSahabi and the closely related site of Toros Menalla in Chad, dated to the late Miocene about 6 to 7 million years ago, preserve the latest fossil record of the group in Africa. African anthracotheres went extinct worldwide shortly thereafter. Big and bulky, Libycosaurus were the largest of their kind. To sustain their body mass their teeth became a virtual buzz saw of cutting blades processing massive quantities of soft marsh plants. They were unique among all other modern mammals in adding a fifth premolar to their impressive battery of teeth. The paleontology of the AsSahabi anthracotheres tells an important story of environmental change. Unlike other earlier anthracothere habitats, AsSahabi does not preserve coal forests or lignites. There were large trees at AsSahabi forming a riverine forest but the widespread and dense tropical forests that had once covered wide areas of Africa had disappeared. Some trees at As Sahabi even show scarred rings caused by savanna bush fires. Half of the small mammals that have been found at AsSahabi are dry adapted gerbils, showing that open country and probably even incipient desert conditions were only a short distance away. The species Libycosaurus petrocchii apparently did not luxuriate in a swamp forest as had its ancestors but held on for dear life in the marshlike fringes of a major African river surrounded by encroaching desert. Its lifeline was the EoSahabi. When the river dried up, the African anthracotheres would disappear forever. The anthracotheres tell us, in context with the rest of the AsSahabi fauna and flora, that there were rapid and major habitat transitions in the latest Miocene of North Central Africa � swamp forest to neardesert within a distance of only a few hundred meters. 7 International Institute for Human Evolutionary Research Occasional Paper 1 An Ancient Bioprovince and A River that Ran Through It Unlike the rest of Africa, northern Africa borders the Mediterranean Sea, and a good part of its environmental uniqueness derives from this fact. Beginning about 7 million years ago during the Messinian stage of the late Miocene Epoch, the Mediterranean Sea began to evaporate, probably due to a cutting off of inflowing waters from the Atlantic Ocean at Gibraltar. Like a giant bathtub with the faucet turned off, the Mediterranean Basin cooked in the hot sun until large parts of it were a parched, saltflat desert. This was a land bridge between Africa and Eurasia but not one that many animal species could cross. Stegotetrabelodon was one animal which did cross the Mediterranean Basin. Its fossil remains have been found at the southern tip of Italy. Dry conditions spread generally across northern Africa, the incipient Sahara Desert, as the region fell into the giant rain shadow of the uplifting Himalayas far to the east. Life huddled around lifegiving rivers that flowed out of tropical Africa to drain into the Mediterranean. Because of these isolating environmental conditions, North Central Africa preserves a unique LibycoChadian fauna at this time. There are many endemic species, led by Libycosaurus petrocchii, a species absent from contemporaneous fossil sites in other parts of Africa. Some species, the ones that could disperse across open country, could migrate out of the region and are found elsewhere. Most of the animals at AsSahabi that are shared with other fossil sites in Africa and Asia are the carnivores like lions and hyenas, savanna pigs, Stegotetrabelodon, opencountry ungulates like antelopes and threetoed horses, and dry adapted rodents like the AsSahabi gerbil. It is at first surprising that hippopotamuses are one of the groups from AsSahabi that are shared with other sites in Africa, but unlike the water and marshbound anthracotheres, hippos are grazers that easily walk over open country for many kilometers looking for grass. The ancient primate cosojourners of anthracotheres must also have undergone severe selective pressures as forests shrank and food resources dwindled. The Habitat of the Plains AsSahabi records the transition away from the ancient African forests to the brave new world of the plains and savannas. If we imag ine ourselves leaving the river bank after a refreshing drink in the EoSahabi river, we would soon pass through the riverine forest, emerging to see before us the extensive grass covered plains of Africa. Here only acacia trees and low bushes sparsely dot the landscape but there are many mammals to be seen. The ani mals of the African plains are for the most part cursorial � they have limbs and bodies with running adaptations. The habitat that they inhabit would be familiar to us today because it spread widely in Africa after the late Mio cene as climate generally became drier over most of the continent. Although there are no more habitats like this in northern Africa, the Serengeti Plain in Tanzania, Virunga National Park in the Democratic Republic of Congo, and Kruger National Park in South Africa would be quite similar. Paleontologists term the fauna from the plains habitat at AsSahabi the "distal" community because it is far away from the actual site of waterlaid fossil deposition. Fossils of these animals must be "brought in" � by the action of flowing water or by the scavenging activi ties of other animals. Despite this transport, which leads to fossils from the plains being generally more fragmentary than those from the nearriver community, most of the species 8 Boaz Libya Before the Sahara The open country or "savanna" habitat at AsSahabi during the rainy season. A group of Pachy crocuta hyenas scavenges a kill of the antelope Miotragocerus in the foreground, as the small carnivore Viverra howell looks on. Maribou storks and two running hyenas (Chasmaporthetes) keep their distance from the kill. A shallow water hole is a focus for plains animals and has at tracted hippos (Hexaprotodon sahabiensis), Dytikodorcas lybicus, the most common AsSahabi antelope (right), hippotragines, and Raphicerus (left). The running savanna hog (Nyanzachoerus syrticus) is shown in the middle right foreground. A group of threetoed horses (Cremohipparion) gallops in the left background. A hypothetical group of Sahelanthropus, a yet tobeconfirmed "ghost species" at AsSahabi, rests in the shade of a Celtis tree. diversity at AsSahabi is paradoxically from this habitat. This is a testimony to how biologi cally productive the teeming plains of Africa had become. Antelopes were the most numer ous largemammal denizens of this habitat. The most common antelope at AsSahabi was the antilopine Dytikodorcas lybicus. Antilo pines are opencountry antelopes in Africa today. Most of the other antelopes belong to opencountry or bushadapted groups. Signifi 9 cantly there are no forest or dense bush ante lopes known. Threetoed horses of as many as four species are present at AsSahabi. Not as large or as fast as the singletoed zebras of today, their limb anatomy and highcrowned chewing teeth indicate that they frequented the open spaces and grazed on the tough grasses that grew there. A running hyena (Chasmaporthetes), whose limb proportions resembled those of the modern cheetah, and International Institute for Human Evolutionary Research Occasional Paper 1 a pig with long legs (Nyanzachoerus syrticus) were also species which had adapted to cover ing large territories in their quests for food in the vast open plains. Primitive giraffes and rhinoceroses lived here too but were rare. by the EoSahabi river drainage basin. We hypothesize these species to have been at As Sahabi but so far have not found them. Certainly the most talkedabout AsSahabi ghost species is hominids, the bipedal ancestors of ourselves. A few fragmentary fossils that might be apes or hominids have been found at AsSahabi but they are not definitive. A skull of the earliest known hominid, Sahelanthropus tchadensis, was discovered in 2001 at Toros Menalla, around the headwaters of the EoSahabi river in Chad, strengthening the case for hominids as a ghost species at AsSahabi. But what kind of ghost species would the earliest hominids be? Unlike owls, hominids would not likely have left a paleontological signature of their presence. But are they similar to the bush babies, living in the riverine forest close to the anthracotheres, the ecological companions of their ape ancestors, or are they out on the plains with the rare dogs and rabbits, carried there by their new method of locomotion, bipedal walking? Only time and much more fossil exploration of the fossil sediments at As Sahabi will tell. What is clear is that hominoids of whatever ilk would have had to adapt to profound changes in late Miocene environ ments or go extinct. AsSahabi may eventually tell us much about the earliest evolutionary emergence of our hominid ancestors. Ghosts at AsSahabi There are some animals that we know must have been present in the ancient habitats at AsSahabi but whose fossil remains we have not yet discovered. Until their presence is confirmed we may well term these animals "ghosts" � shadowy creatures whose actual existence cannot be proven. One example of such a ghost species at AsSahabi is owls. These birds hunt by night and feed on small mammals. They then nest during the day in trees (near the river) where they disgorge "pellets" containing all the indigestible teeth and bones of their prey. Owl pellets are almost certainly the sources for most or all of the small mammal fossils that we have discovered from the distal plains habitat at As Sahabi. We have the owls' signature in the fossils but not their actual remains. Another category of ghost species includes species whose habitats are present at As Sahabi, whose fossil antecedents are present elsewhere at earlier fossil sites, and which have modern descendents in Africa. A prime example of these ghosts are prosimian primates. We have discovered a forestliving insectivore, a shrew, at AsSahabi, and we have the fossil wood that documents the presence of forest trees. But so far fossils of small nocturnal ghostlike primate species like the living African bush baby have eluded us. A third category of ghosts are rare species that have been found at other sites that just by chance or bad luck have not yet turned up at AsSahabi. Dogs, rabbits, and aardvarks are plains animals discovered at the late Miocene Chadian site of Toros Menalla, to the south of AsSahabi, of similar age, and connected to it 10 Boaz Libya Before the Sahara Acknowledgements Prof. Giuma Anag is thanked for suggesting the writing of this article. Shell Exploration and Production Libya GmbH generously pro vided funding for field research, museum de velopment, and for the preparation of this publication. Marc Gerrits, Alex Battaglia, and Carlo Nicolai are thanked for their support and continuing interest and involvement. The U.S. National Science Foundation RHOI Pro gram is acknowledged for its support of the AsSahabi Research. Colleagues at the Gary ounis University Earth Sciences Department, Benghazi, Professors Ali ElArnauti, Ahmed El Hawat, and Fathi Salloum, and the Garyounis University Research Center, directed by Prof. Kilani Kilani, have supported the AsSahabi research from the beginning. Director of the Department of Archaeology Giuma Anag and the staff of the Libyan National Museum are thanked for their invaluable support and as sistance in researching and preparing this publication. The many members of the East Libya Neogene Research Project, and its predecessor, the International Sahabi Re search Project, are thanked for their diligent fieldwork and rigorous analyses that support this popular article. Thanks are due to Libyan codirectors of the East Libyan Neogene Re search Project, Ahmed Muftah and Moftah El Shawaihdi, and to all members of the ELNRP, especially Prof. Paris Pavlakis and doctoral student Dimitris Michailidis of the University of Athens Historical Geology Department for assistance. Finally, artist Antonio Varelas is thanked for his diligence, patience, and per severance in researching and completing the artistic reconstructions. 11 For Further Reading Boaz, Noel T. 1998 Quarry. Closing In on the Missing Link. New York: Free Press. Boaz, N., A. ElArnauti, P. Pavlakis, and M. Salem (eds.) 2008 CircumMediterranean Geology and Biotic Evolution During the Neogene Period: The Perspective from Libya. Benghazi, Libya: Garyounis University. Garyounis Scientific Bulletin, Spec. Issue 5. ElArnauti, A. and A. ElSogher 2004 Short Notes and Guidebook on the Geology of Qasr As Sahabi Area. Sedimentary Basin of Libya, Third Symposium, Geology of Libya. Tr�poli: Earth Science Society of Libya. Gibbons, A. 2007 The First Human: The Race to Discover Our Earliest Ancestors. New York: Anchor.