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Puzzling Out Man’s Ascent

27 minute read

It is one of the least hospitable places on earth. A steady wind moans over the crocodiles basking on the banks of blue-green Lake Turkana and flattens the knee-high beach grass where the long-horned oryx graze. Beyond stretches the desert of northeast Kenya, baked by the African sun. In a wadi, or dried-up stream bed, not far away, a sandy-haired man moves slowly, his loose shorts and shirt flapping in the breeze, his head bare to the sun, his eyes searching the arid soil at his feet. Some 50 ft. away, sandals scuffing dust into the air behind her. his wife keeps pace, her eyes sweeping the ground. An African, remainder of the party.

Suddenly the leader stops, stoops and snatches a small brownish fossilized bone fragment out of the sand. “Nimeipata, ” he says in Swahili to the man beside him. “I’ve got it.” Then, “Meave!” he calls to the wom an, who runs to join him. Together they examine the bone for a moment, replace it on the exact spot where it was found, mark it with a stake, and resume their search.

The intent man in the desert is Richard Erskine Leakey, heir to one of the greatest surnames in anthropology and, at 32, a formidable scientist in his own right. He and his dusty band are looking, almost lit erally, for footprints in the sands of time, for clues to the mystery of man’s origins. Their ambitious goal: to establish the nature of the creatures that veered off from the ancestral line of apes onto the evolutionary path that eventually led to man. In this pursuit, Leakey’s team has turned up at the Turkana site alone more than 300 fossilized bone specimens, from an estimated 1 80 of man’s ancestors. All told, during a decade-long Leakey has found more and better pre-man and early man fossils than any other anthropologist. His work has helped upset many held ideas on evolution and has forced science to write a new sce nario for man’s slow progress from ape to Shakespeare’s “paragon of animals,” Homo sapiens.

Elsewhere around the world, other scientists are examining fossils, stone tools, soil and rock samples, and even pollen grains in an effort to find more of the missing pieces in the puzzle of man’s ascent. They are motivated not only by curiosity and dedication to their science but also by the knowledge that what they discover may help man to understand himself. Says Leak ey in his just-published Origins (Dutton; $17.95): “By searching our long-buried past for an understanding of what we are, we may discover some insight into our future.”

Long before the search for relatively contemporary roots be came a popular pastime, man sought to account for his ultimate origins. In the Middle Ages he looked to the Bible for the answer Turning to the book of Genesis, which says that God created man on the sixth day. James Ussher, the Archbishop of Armaugh, decided in 1650 to determine when that day had occurred By calculating backward through all the biblical “begats” he figured that man was created in 4004 B.C. John Lightfoot, master of St. Catherine’s College at the University of Cambridge, shortly thereafter pinpointed the time of the momentous event even more precisely. He announced that it had occurred on Oct. 23 at 9 a.m.

The finding of crude tools, weapons and other evidence of man amidst the fossilized bones of long-extinct animals-and the growing sophistication of geologists and biologists— had all but discredited the Ussher-Lightfoot calculations by 1859, when Charles Darwin published On the Origin of Species. Although Darwin did not discuss man in this work, the theory of evolution of species through natural selection suggested that human beings had evolved from some lower form of life. By implying that man was related to apes and monkeys, the great naturalist incurred the derision —and wrath—of millions round the world. “Descended from apes!” exclaimed the wife of the Bishop of Worcester when she heard the news in 1860. “Let us hope it is not true, but if it is, let us pray that it will not become generally known.”

Her prayers were not answered. No less a scientist than Biologist Thomas Henry Huxley further espoused the idea in his 1863 Man’s Place in Nature. Darwin won many new converts to his concept in 1871 with the publication of The Descent of Man. Most convincing of all, the fossil record continued to reveal that man had not always existed in his present form. That more primitive men might once have walked the earth was suggested when a skull was found at Gibraltar in 1848 that was more evolved than the skulls of apes but less so than that of modern man. Then in 1856, a similar skull, unearthed in the Neander Valley outside the German city of DÅ­sseldorf, showed that at least one of man’s probable ancestors (later named Neanderthal man) had a low, sloping forehead, a receding chin, and thick ridges over his eye sockets. Java man, discovered by a Dutch doctor who found a skullcap, or cranium, in 1891 and a thighbone in 1892, was obviously an even earlier, less evolved specimen than Neanderthal. Teeth, a nearly complete skullcap and bone fragments discovered in a cave at Choukoutien, China, during the 1920s established the existence of yet another early ancester, Peking man.* These discoveries helped to convince the remaining skeptics that the earlier finds were not the remains of a freak ape or a deformed human. The ancient, erect-walking creatures had apparently been plentiful and widely distributed; it now seemed indisputable that modern man had evolved from more primitive ancestors. But still not even those who acknowledged his age had any clear notion of man’s antiquity. Even the evolutionists saw the whole course of human development as a fairly recent phenomenon, and no one had any real conception of its causes.

In 1924 Raymond Dart, the South African anthropologist, found a startlingly different skull embedded in a piece of limestone from a quarry at Taung—Tswana for “place of the lion”—about 120 kilometers (75 miles) north of Kimberley. Dart determined that the skull had come from a five-year-old primate (the order of mammals that includes humans, apes and monkeys) who had lived on the threshold of humanity. Still, he recognized that the creature was even more primitive than Java man. He named it Australopithecus africanus, or the southern ape of Africa. The skull displayed an odd blend of ape and human characteristics. Dart’s creature clearly had a large, apelike face, but its teeth were proportioned like those of a modern man. Its brain, although far smaller than that of a human child, had nonetheless been larger than an ape’s. Perhaps most significant, the creature had walked upright. Its foramen magnum, the hole through which the spinal cord enters the skull, was not in the rear of the skull as it is in an ape or any other animal that walks on all fours; as with Neanderthal. Peking and Java men, it was far enough forward in the skull to indicate that the spinal column was usually in a vertical position and that the young primate had been bipedal.

In 1936 the skull of an adult Australopithecus africanus was unearthed from a mine at Sterkfontein, in the Transvaal. From it, Robert Broom reconstructed a creature similar to the one found at Taung—an ape-man somewhat more than a meter (3 ft. 3 in.) in height, with upright posture and human-like teeth but a low forehead and a small brain. Two years later Broom uncovered a new type of the southern ape a mile away, at Kromdraai. The creature, later called Australopithecus robustus, was heavier and larger than the earlier South African finds, and had bigger teeth, set in a nutcracker-like jaw.

Even more surprises were in store. After World War II, the radioactive carbon-14 dating method was developed by U.S.

Chemist Willard Libby. This was followed by the invention of the potassium-argon method. Both gave scientists techniques by which they could accurately determine the age of the strata in which fossilized bones were found, and sometimes the age of the bones themselves. Using these new tools, they have determined that Java man and Peking man, now classified as Homo erectus, walked the earth more than 500,000 years ago.

In the late 1950s the anthropological team of Louis and Mary Leakey—Richard’s parents—began finding, at Olduvai Gorge and other East African sites, remains similar to those uncovered by Broom. They produced convincing evidence that the massive-jawed robustus, which weighed 45 to 67.5 kg. (100 to 150 lb.), existed in the region nearly 2 million years ago. In the same deposits, the Leakeys also discovered pebbles chipped to form sharp-edged implements—evidence that even so far back, man’s ancestors knew how to make tools.

But who? For a time, many thought the finds showed that the hulking robustus had been intelligent enough to make tools. Then in 1961 Jonathan Leakey, another of Louis’ sons, unearthed parts of a 1.8 million-year-old skull that failed to fit easily into the familiar Australopithecus mold. The creature’s teeth were more manlike than those of Australopithecus and the brain was larger; whereas Australopithecus brains averaged 450 to 550 cc. in volume, the cavity of the skull found by Jonathan Leakey indicated that it had contained a brain measuring nearly 700 cc. That was considerably smaller than modern man’s brain—which averages 1,400 cc.—but large enough to suggest that it had belonged to a being that fit ideally between Australopithecus and Homo erectus. Louis Leakey and his colleagues named him Homo habilis (handy man), because they believed him to be the manufacturer of the tools found in the vicinity.

But the skull raised a new problem. While anthropologists could accept the idea of man having evolved from Australopithecus, the evidence seemed to show that Homo habilis lived at the same time as his less advanced cousins. If so, could he have descended from them? Also, if several species of pre-men lived side by side, which one was really man’s ancestor?

A surge of discoveries in recent years has brought anthropologists closer to the answer. In 1972 Maurice Taieb, 40, of France’s National Center for Scientific Research, and Donald Carl Johanson, 34, of Case Western Reserve University and the Cleveland Museum of Natural History, found stone tools dating back 2.6 million years in the Afar region of Ethiopia. Two years later their team made an even more dramatic discovery. Not far from their first find, they uncovered the fossilized remnants of a 20-year-old female Australopithecus lying in a layer of sediment 3 million years old. Unlike most other fossils of early man —a tooth here, a bone fragment there, occasionally a portion of a skull—this one comprised a good part of the skeleton.

Named after the Beatles’ song Lucy in the Sky with Diamonds, Lucy was a small creature, not much more than a meter tall, with a brain capacity about a third that of modern man. Lucy’s skeleton gave scientists their best clues yet to the proportions of Australopithecus, and revealed her to be surprisingly short-legged. But the find left no doubts that she walked erect. The shape of her pelvis showed clearly that she was bipedal.

Other researchers were adding to the evolutionary mosaic. In 1969, after re-evaluating the fragmentary remains of a monkey-size creature called Ramapithecus —found in India’s Siwalik Hills and first described by Yale Paleontologist G.E. Lewis is in 1934—Elwyn Simons, then at Yale, and his former student David Pilbeam became convinced that this creature too was an ancestor. They noted that his teeth were far closer to those of other hominids (manlike creatures) than to those of apes. Indeed, says Simons, 47, who now heads the Duke University Center for the Study of Primate Biology and History, “Ramapithecus is ideally structured to be an ancestor of hominids. If he isn’t, we don’t have anything else that is.”

If Simons and Pilbeam are right, man’s roots have been pushed even further back. Dating techniques have established beyond doubt that Ramapithecus—whose remains have turned up in India, Pakistan, East Africa, the Middle East and Central Europe—was alive and well at least 14 million years ago.

But the most exciting of the recent discoveries have come from East Africa and Richard Leakey, In 1972, Bernard Ngeneo, a Kenyan member of Leakey’s fossil-hunting team, spotted a few scraps of bone exposed by erosion in sandy sediments in a steep gully near Lake Turkana’s eastern shore. Working carefully, the Leakey team sifted scores of additional fragments out of the soil, then turned them over to Meave Leak ey, a paleontologist, and Anatomist Bernard Wood for assembly. As the last pieces of the six -week reconstruction job were put in place, the team mem bers found themselves staring into the empty sockets of a highly evolved hominid. The skull, called “1470” after its National Museums of Kenya catalogue number, was manlike in configuration and, according to Leakey’s measurements, once contained a brain of 800 cc.—more than half the average size of a modern human brain. But what excited the team most was the age of the skull. Probably a Homo habilis, 1470 was more than 2 million years old.

The 1470 skull and a similar find, labeled 1590, proved that Homo habilis—from whom man could have descended—coexisted with Australopithecus, thus weakening arguments that the latter was man’s direct ancestor. Then, in 1975, the Turkana site yielded a Homo erectus skull resembling that of Peking man and with a brain size of 900 cc. The age of the fossil, about 1.5 million years, showed that Homo erectus had emerged even earlier and was hunting in the African plains while Australopithecus still roamed the earth. Because the more advanced Homo erectus was almost certainly a direct ancestor of modern man, the new skull, in the view of some anthropologists, effectively eliminated Australopithecus from man’s ancestry.

The result of these findings is a radical revision of long-held views of evolution. As recently as a decade ago, scientists talked about a direct, unbranching line of descent —Australopithecus, Homo erectus, modern man—one following the other in logical order. Now all that has changed. “We can no longer talk of a great chain of being in the 19th century sense, from which there is a missing link,” says Phillip Tobias, 51, Dart’s successor as professor of anatomy at the University of the Witwatersrand medical school in Johannesburg. “We should think rather of multiple strands forming a network of evolving populations, diverging and converging, some strands disappearing, others giving rise to further evolutionary development.”

Anthropologists now believe that man’s family tree (see chart) goes back to a primate called Dryopithecus, a true ape that appeared some 20 million years ago. Much later—by 14 million years ago—the Dryopithecus line had split into three branches.

One branch evolved into the ancestors of today’s great apes—the gorillas, chimpanzees and orangutans, which are man’s closest living cousins. Another produced a creature called Gigantopithecus, a huge ground ape that roamed the valleys of Asia for a few million years before it became extinct. A third branch gave rise to Ramapithecus, which most anthropologists believe was a distant ancestor of man.

The cause of the changes can be traced, at least in part, to plate tectonics, the movement of the great crustal plates that ride on the earth’s semimolten mantle and provide its solid outer shell. Some 45 million to 50 million years ago, the plate that carries the Indian subcontinent was pushing up into the underbelly of Asia, slowly thrusting up the massive mountain range now called the Himalayas. This new barrier to global wind circulation helped change weather patterns, altering average temperatures around the world. By about 14 million years ago, climates that had been tropical had turned largely temperate, jungles had thinned out, and fruits and nuts normally available year round began to appear only seasonally.

The changing food supply offered new opportunities for feeding outside the forest. Some of the forest-dwelling apes began venturing into the savanna, or grasslands, in search of food such as roots, seeds and finally the meat of other animals.

The creature most likely to have resulted from this transition, anthropologists believe, was Ramapithecus. Anthropologists theorize that once out of the forest, Ramapithecus began to evolve rapidly. The process of natural selection favored those of his genus who could stand up; an erect position enabled them to see over the tall grass to spot and hunt their prey—and to see and escape the carnivores that preyed on them. Thus they were able to survive longer and produce more offspring, who shared their physical characteristics. After many generations of selection, the savanna-dwellers had evolved into upright-standing animals distinctly different from the forest-dwelling relatives they had left behind.

Though scientists have found practically no telltale fossils from the crucial period between 8 million and 5 million years ago, anthropologists speculate that some time toward the end of this period the hominid line split into the species Australopithecus robustus and africanus. There was also a third species, which some anthropologists believe branched off at the same time, and others think evolved later from A. africanus. Whatever the case, it is generally agreed that the third species was not an Australopithecus, but the first creature that could rightfully be called Homo—a man.

Scientists believe they are closing in on the time when this earliest form of man emerged. Fossil evidence shows the split that produced the first human must have occurred longer ago than 3.5 million years—the age of the oldest known Homo fossils, which were found in 1975 by Mary Leakey. Again, the rigorous demands of savanna living may have been responsible for the branching out. Australopithecus africanus, straining to augment its food supply in the flat grasslands, began to eat meat—probably obtaining it not by hunting, but by scavenging the kills left behind by large predators. Australopithecus robustus, on the other hand, continued to subsist largely on seeds and nuts. Both eventually died out, unable to compete successfully with the large predators or with Homo. who was coming into his own.

While his Australopithecus cousins foraged or scavenged, Homo habilis began to make tools and to hunt. Both actions accelerated his evolution. Toolmaking, which required reasoning and more complex neurological hookups, gave a survival advantage to the creatures with the biggest brains. That led to an increase in brain size. Hunting, with its emphasis on outwitting animals that were either faster, stronger or fiercer than the hominids that hunted them, also stimulated rapid brain growth. In addition, says Milford Wolpoff of the University of Michigan, it placed a premium on cooperation, strengthening the bond between members of the group and starting man on the road toward developing language.

These developments, probably more than any others, hastened the differentiation between man and earlier hominids. Explains Anthropologist Charles Kimberlin (“Bob”) Brain of the Transvaal Museum in Pretoria, South Africa: “Meat eating and hunting were important factors. If you remained a vegetarian, the necessity for culture was not nearly as great.” Richard Leakey too believes that hunting helped to make emerging man a social creature. Says he: “The hominids that thrived best were those able to restrain their immediate impulses and manipulate the impulses of others into cooperative efforts. They were the vanguard of the human race.”

Still, doubts about the sequence of man’s emergence remain.

Scientists concede that even their most cherished theories are based on embarrassingly few fossil fragments, and that huge gaps exist in the fossil record. Anthropologists, ruefully says Alan Mann of the University of Pennsylvania, “are like the blind men looking at the elephant, each sampling only a small part of the total reality.” His colleagues agree that the picture of man’s origins is far from complete.

Perhaps no one is trying harder to fill in the blanks than Richard Leakey. Picking up where his father Louis left off at his death in 1972, Richard—with his Lake Turkana discoveries —has already moved to the forefront of modern anthropology. Now he is reaching out to coordinate research throughout East Africa and taking the lead in sorting and assembling the thousands of fragments of evidence that may someday reveal the secrets of man’s origins.

In a sense, Leakey was born for his role. From the age of six months, he was taken on expeditions with his famous parents and learned to recognize fossils almost before he could talk. His childhood conversations were filled with the anatomical, geological and biological jargon of anthropology. His father —a Church of England missionary’s son who was raised almost entirely in the African bush—taught “bushcraft” to Richard and his brothers Jonathan and Philip by sending them out to scavenge and survive in the wild. But as Richard grew up, he became restive living in the shadow of strong-willed and often autocratic Louis Leakey. “I was determined to make my own name,” he recalls, “and I couldn’t do that in my father’s field. I had to go off on my own.”

He did. For years Richard had escorted visiting scientists to his parents’ dig at Olduvai and taken them around East Africa on courtesy safaris. In 1960, at the age of 17, he left school without graduating and set up a safari business on his own. The business did well, but Richard soon yearned to be back in the digs. Then, in 1963, on a chance flight over Lake Natron in northern Tanzania, he spotted what looked like interesting sediment beds and, encouraged by his parents, set off to explore the area. His first expedition proved to be a success; the team he assembled found a fragment from an Australopithecus robustus. He decided to become an anthropologist.

Convinced that he needed to broaden his scientific background, Richard left for London to catch up on his secondary-school studies, completing two years of work in seven months. He then passed his university entrance exams, but the next term was not scheduled to start for another nine months. Deciding that he did not have that much time to waste, Richard went home to Nairobi. He still does not hold an academic degree and has never returned to a campus—except as a speaker.

Back in Nairobi, young Leakey began rebuilding his neglected safari business and married Margaret Cropper, a young researcher who had been his mother’s assistant at Olduvai. But he could not stay away from anthropology. In 1967 he joined an expedition organized by his father to the Omo Valley in Ethiopia. Well before it was over he knew he was ready to strike out on his own. Says Leakey: “I already knew how to organize an expedition and how to find fossils. I wanted to have my own show.”

It was not long in coming. In 1968, Richard accompanied his father to Washington for a meeting with the National Geographic Society’s research committee and listened patiently as his father outlined plans for the coming year. Then, when the committee members turned to him, he surprised them by outlining some plans of his own. He had spotted some intriguing sediment layers and stone tools during a brief reconnaissance at Lake Turkana and asked for funds to go back for a closer look. Taken by his brashness, the committee granted his request. But it came with a warning: “If you find nothing you are never to come begging at our door again.”

Young Leakey’s self-confidence was justified; the Turkana region has proved to be an anthropological mother lode. In a basin several kilometers deep, walls of strata lie exposed, many-layered sandwiches of volcanic ash and ancient sediments containing the remains of complete prehistoric environments. Organizing a team of fossil hunters, Leakey established a base camp at Koobi Fora, a mound at the inboard end of a long, crocodile-infested sand spit that curves out into the lake. Then he began following his nose—with remarkable success. Turkana has yielded the richest accumulation of remnants of man and his predecessors ever found in one area.

Louis Leakey did not take kindly to the acclaim that began pouring down on Richard. For years Louis had dominated African anthropology, at least in part by intimidating his rivals. But the elder Leakey’s rugged existence was beginning to exact its toll. Never one to take care of himself, he had been suffering for years from the cumulative effects of tropical diseases, concussions, bee stings and snakebites. He had also seen his son assume the directorship of the National Museums of Kenya. Now the conflict between the two became so intense that it threatened to split the family. Mary began to spend more and more time away at Olduvai, while Louis and Richard pointedly avoided each other. Says Richard: “He was a sick old man at the end of his career, and he found my successes very difficult. I was not old enough or mature enough to respond to that adequately.”

The feud had ended in 1972 when the elder Leakey flew to Koobi Fora to spend an exciting evening with his son, examining fossils late into the night by the harsh light of a gas lantern. That night Louis predicted that Richard would find evidence of three hominid species at Turkana. A few weeks later, he died, unaware that events would prove him right. Says Richard: “I think his sheer dogged persistence—and his follow-through on ideas to the point where they were proved either right or wrong—was his greatest gift. In many ways, his greatest achievement was his ability to stimulate others.”

The same qualities seem to have passed on to Richard, who resembles his father in more ways than even he cares to admit. “Richard’s just like the old man,” says a colleague who has worked with both. “You could talk to either one of them and know he was in another world thinking about some theory and not hearing a word you said.” Says Brother Jonathan: “Just like his father, Richard is involved in ten different things at the same time. He’s very ambitious.”

Richard does not deny it. Still director of the National Museums of Kenya, he is also a research associate of the recently created International Louis Leakey Memorial Institute for African Prehistory. He is determined to help build both into major centers for the study of man’s origins. A citizen of Kenya, he has always made a point of taking students from Nairobi University on his expeditions (“Nobody ever used local students before, but we cannot exclude our own people”).

A few anthropologists still look down on Richard Leakey, regarding him as an untrained upstart without proper academic credentials. But most of his colleagues believe he has more than made up in acquired knowledge for any lack of academic initials to place after his name. Yale’s Pilbeam calls Leakey the “organizing genius” of modern paleoanthropology (the study of fossil hominids). Mary Leakey, a vigorous, cigar-smoking woman of 64 who still puts in eight hours a day exploring Olduvai, is also impressed. She says her son “is rather better than Louis was. I’m quite proud of him.”

These days Leakey spends most of his time in Nairobi, mired in administrative work at the museum. But he still longs to be out in the field and at every opportunity loads his second wife, the former Meave Epps (his first marriage ended in divorce), and their two small children into his four-seat Cessna and flies out for a short stay at Koobi Fora.

Next summer, however, Leakey will lead a team to search south of Lake Turkana at a site called Suguta. The region is roadless, and he will have to go in, as in the old days, by donkey and camel. The discomforts may be worth it; a geological survey of the area shows fossil-bearing sediments between 5 million and 9 million years old, laid down in a period that has so far yielded few clues about the ascent of man.

Leakey’s colleagues are making plans of their own in the continuing search. Prevented by war from continuing their work in Ethiopia, Johanson and Taieb plan to look for relics of early man in Arabia, where geological and climatic conditions are similar to those in the Afar region where Lucy was found. Pilbeam will soon go back to Pakistan in search of “new surprises.” Simons is heading for Egypt in search of fossils that could enable him to trace man’s roots back beyond Dryopithecus.

As the patient searchers discern more and more about early man and his predecessors, they also may gain an ever-widening insight about modern man, his nature, his failings and his future. Most major anthropologists reject the notion popularized by Robert Ardrey (The Territorial Imperative) and others that man is inherently aggressive and that his murderous instincts derive from his apelike origins. Indeed, they have found no evidence in their digs that man was anything but a peaceable hunter-gatherer before the invention of agriculture some 10,000 years ago. It was farming, they believe, that created settlers with property to protect and fostered cultural differences that led to antagonisms between races and communities.

Richard Leakey’s life work, in fact, has made him impatient with those of narrow ethnic and national perspectives. He makes it clear to all that he is a Kenyan and proud to be a citizen of that African nation. Furthermore, he notes that racial differences, as they are commonly perceived, are a superficial and recent development, having arisen only about 15,000 years ago. Says Leakey: “I am aghast that people think they are different from each other. We all share a tremendous heritage, an exciting bond. We are all the same.”

Leakey has learned another object lesson from his probes into the past. Increasingly concerned about overpopulation, environmental abuses and the depletion of natural resources, he fears that man may not be able to cope biologically, that he cannot genetically change fast enough to survive the ever-more-hostile environment he is creating. Says he: “People feel that we are here by predestination and that because we are humans we will be able to survive even if we make mistakes.” But, cautions Leakey, these people have no perspective on the fact that humans are living organisms. “There have been thousands of living organisms,” he says, “of which a very high percentage has become extinct. There is nothing, at the moment, to suggest that we are not part of that same pattern.” He notes that there is one point of difference: man is the only organism with power to reflect on its past and upon its future. That power to reflect, he says, “is what makes us able to plan our future in such a way as to avoid what seems inevitable.”

* The bones of Peking man, turned over to U.S. Marines in China shortly before the Japanese attack on Pearl Harbor in 1941. soon afterward mysteriously dis appeared. Despite a longstanding offer of a $150,000 reward— finally withdrawn this month — they have never been recovered.

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