The Sediments of Time

by Meave Leakey

  Courtesy of Samira Leakey

  The Koobi Fora spit, where we had our base camp for many years, proved a magical setting with abundant birds and wildlife. It was also a strategic location to defend against roaming bandits as it was protected by the lake on three sides.

  Courtesy of Fraser Smith

  Preparing large fossil specimens for safe transportation back to Nairobi was an elaborate process that involved reinforcing them with branches and encasing them in protective hessian sacking covered with plaster of paris.

  Courtesy of Fraser Smith

  Richard and I revisit some of our early finds at the National Museums of Kenya in 2020. We enjoy an intellectual debate about human evolution to this day.

  Courtesy of Marta Lahr

  12

  Early Homo: A Horrible Muddle

  Flat Face opened Pandora’s box by disproving that the single ancestor for the human line began with Lucy at slightly more than three million years. Johanson and White’s simple family tree—with a single forked branch leading from the A. afarensis stem to the robust australopithecines on one twig and Homo on the other—was in tatters. K. platyops has to fit in there somewhere. But where? And the incontrovertible evidence of our having more than one possible ancestor begs the bigger question: did we evolve from an early megadont australopithecine or from something else?

  Part of the problem is that the minute we start talking about our own, human, line, emotions start to fly. Much stronger sentiments accompany any decision about designations to the genus Homo than any other. Perhaps this is why Darwin picked the humble barnacle as his study subject when he set out to find evidence to support his theory of evolution. The very mention of our own genus resonates with a deep and compelling desire to know where we come from, and opinions have been governed more closely by emotions than science. People all too frequently have unstinting confidence in the truth of their convictions, however weak or contradictory the evidence may be. Fuelling this cocktail is the frustrating paucity of new specimens to resolve old disputes.

  The first sensational discovery of a fossil human ancestor in Asia by Eugène Dubois in 1891 in Java is the earliest example of this. This discovery, which came to be known informally as Java Man, owes a great deal more to serendipity and dogged determination than any well-founded expectation of success. Dubois was Dutch and completely fixated with the notion of finding the “missing link,” then known purely hypothetically as Pithecanthropus alalus. (Although no such creature had been found at the time, a biologist named Ernst Haeckel had postulated that such an “ape man without speech” was only awaiting discovery.) Moreover, Haeckel wrongly believed that humans were more closely related to Asian orangutans and gibbons than African gorillas and chimpanzees. Since Dubois’s opportunities were tied to the location of Dutch colonies, some of which were in Asia, he decided quite logically that Indonesia was the only suitable option available for his search. A doctor by training, Dubois secured a post with the Royal Netherlands East Indies Army as a medical officer in 1887 and staked everything he had on the chance of finding his beloved missing link in what was then the Dutch East Indies. Prevailing against bouts of high fever from malaria, hellish tropical heat, and difficult conflicts with his field crew, Dubois struck gold relatively quickly, finding first a molar and then a skull cap with unmistakeably human attributes at a site called Trinil. Hot on the heels of this momentous discovery, Dubois’s team returned to work in 1892 after the rainy season and unearthed a complete thigh bone that showed uncontrovertibly that his hominin walked upright, which led Dubois to give it the appellation Homo erectus.

  Dubois paid a heavy price for the audacity of his discoveries, which went against the conventional wisdom of his time. Darwin’s idea that humans evolved from apes was preposterous enough. But Dubois’s fossils hailed not from Europe but from the Far East. Worse still, the association of such a modern-looking leg bone with such a primitive skull cap was cause not only for great consternation but derision and ostracism from the scientific community. Dubois was devastated and became increasingly reclusive and possessive of his fossils, refusing to allow any researchers to see them for many years.

  Over the decades since Dubois’s first discoveries, there have been a great number of other important and exciting finds in Asia. Initially, all the evidence of H. erectus was in Indonesia, where Dubois was based. Several decades after Java Man was unearthed, a site in China would make headlines. At this time, in the early 1920s, a great deal of confusion was caused by the fraudulent Piltdown Man, which was constructed from the skull of a modern human and an adulterated jaw of an orangutan with the teeth carefully filed down to present the comforting impression that our human ancestor was large-brained and, most important, British. Nevertheless, scientists had by then accepted Dubois’s finds as genuine hominins, and Asia was considered a legitimate place to search for human origins. Davidson Black, a young Canadian physician, was one of the scientists who had collaborated on the interpretation and study of the Piltdown fake fossils and, like Dubois, was obsessed with finding the missing link. He secured himself a post at the Peking Union Medical College in 1919, and in between his teaching duties, he made forays to various caves, most notably to Dragon Bone Hill in the Zhoukoudian cave system. Following the discovery of an initial hominin tooth, extensive excavations ultimately yielded a skull cap in 1929 that was even more complete than Dubois’s Java Man. This came to be known as Peking Man (Sinanthropus pekinensis).

  In retrospect, this fabulous fossil seems to have been ill-fated from the outset. Excavated by dim candlelight in the cramped recesses of a cave, it was extracted dripping wet and rendered dangerously soft and fragile from the heavy clays. The leader of the excavations, Pei Wenzhong, arranged a continuous shift to carefully turn the skull over a fire to painstakingly dry it out. Then it was wrapped in glue-soaked gauze before being bundled up in numerous protective layers and dispatched by bus to what was then Peking. In spite of the prodigious care taken to protect this valuable fossil, geopolitics would ultimately seal its fate—along with numerous other irreplaceable finds representing at least fifteen hominin individuals recovered from the Zhoukoudian excavation over the following decade. In 1938, the excavation was abandoned because of the increasing interest in the site shown by the Japanese who had already overrun large parts of China by then.

  By this time, Black had died and been succeeded by a German Jew, Franz Weidenreich, who had fled Europe for a life of exile in America before agreeing to replace Black in China. Fearing the degree of interest shown by the Japanese in the fossils and concerned that they would be looted, Weidenreich took meticulous notes, photographs, drawings, and measurements of all the hominin specimens and cast replicas of every bone. The director of the Chinese Geological Survey then decided that the fossils should be smuggled out of the country, and a careful plan was secretly hatched. The fossils were to be transported to the port of Qinhuangdao by US marines and picked up by the SS President Harrison. But in the ensuing chaos after the Japanese bombed Pearl Harbor on December 7, 1941, the fossils vanished and were never seen again. Thank goodness for Weidenreich’s foresight and his meticulous records and casts; for without these, Peking Man and his kin would have been lost to science forever.

  Meanwhile, another intrepid and daring individual was flying in the face of conventional wisdom by looking for human ancestors in East Africa—my future father-in-law. A German butterfly collector, Wilhelm Kattwinkel, was the first to notice the wealth of fossils at Olduvai in 1911. Louis first visited the site in 1931 after seeing some of the fossils collected by Kattwinkel and a subsequent German expedition to Olduvai in 1913. Louis straightaway found many stone tools and fossils of other animals that persuaded him of the huge potential of the site. It was this conviction that made him return to Olduvai again and again over the following decades, adamant that humans had their origins in Africa and that further searching would eventually lead to the discovery of the maker of the stone tools. But Louis had so many ide
as, projects, and potential projects that there was never enough money or time for him to sit for very long in one place. And finding hominins usually takes a great deal of patient searching. It is not surprising that from the time that Louis first started to work at the site until 1955, the only ancient hominin bones to emerge from the gorge were two pieces of a hominin skull. These were found by Mary on her first visit in 1935 when she was twenty-two and very much in love with both Louis and the combined allure of the spectacular landscape and the intriguing artefacts that littered the steep Olduvai slopes. Two teeth, a canine and a molar, are the only other hominin bones they ever found there until 1959, the year that Mary made her momentous discovery of Dear Boy, the first complete Paranthropus boisei ever found.

  Mary writes with characteristic wry humour that Louis “was sad that the skull was not of an early Homo, but he concealed his feelings well and expressed only mild disappointment.” They had been looking for close to thirty years, and Mary had produced a find that was nothing short of spectacular. One can only wonder at the mildness of disappointment she must have felt at his lukewarm response! But even if the skull was not all that Louis had hoped for, it did completely change the nature of their research and many aspects of their lives by attracting funding from the National Geographic Society. So ended the snatched snippets of time they could spend at Olduvai after scrimping and saving to get there. And because they were spending so much more time at Olduvai, a glut of finds soon followed. In a letter dated December 8, 1960, Louis wrote to his close confidante, famed anatomist Wilfred Le Gros Clark, “You may be wondering as others have done, why we are finding so much hominin material now . . . The answer is simple. We have been working continuously now since February, with adequate funds and a huge labour staff, and have already put in some 72,000 man hours this year. Had we been able to do this sort of thing before, we would have had the results before.”

  For Mary, the reward of finding this skull was nothing compared to the joys that lay in the excavation that followed. Mary was an archaeologist, and until she started working with Louis, her only experience was excavating archaeological sites and making exquisite line drawings of much more modern flint artefacts in Europe. She wasn’t particularly interested in the fossils as her great love was stone tools. But other than Mary and Louis, who had seen with their own eyes the vast numbers of tools scattered about the gorge, few people expected that there would be any tools at 1.75 million years. With the new funding, Louis and Mary at last had the money to recruit and train staff to help with the excavations, and this task fell to Mary. She was ferocious in establishing her trademark exacting standards—her meticulous excavation techniques are emulated to this day. Kamoya and Nzube, who formed part of Mary’s team of sixteen men recruited to excavate the skull site, still get exercised today when they recount the rewards and travails of working for the fierce and fastidious matron they came to greatly respect.

  Mary’s new team removed the overburden from an area that covered about 925 square metres (equivalent to a very comfortable house) to reach the level from which the skull had been excavated. Due to the steepness of the slope, this entailed digging down a staggering seven metres at the back of the excavation and removing several hundred tons of earth and rock by wheelbarrow. This enormous pile of dirt still stands today where it was dumped in front of the site, and having conducted so many excavations of my own, I never fail to be impressed by the sheer effort this must have required. Mary’s just reward was 2,470 artefacts. What made the find so significant was that only sixty of these were stone tools. The rest were flakes and debris left over from making the tools. Mary and Louis had long believed that hominins would have been returning regularly to favoured spots to eat and sleep, but they were alone in believing that evidence could be found in support of this. The excavation showed for the first time that the stones had been left there and used deliberately for specific purposes.

  In addition to an assortment of fossils of animals ranging from antelopes to rodents, birds, and even chameleons and lizards, this giant excavation had one further gem to offer: some bones of a second hominin that didn’t seem to square with the robustness of P. boisei. Although Louis initially described these smaller fossils—two lower leg bones, some skull fragments, and two teeth—as Dear Boy’s “wife, mistress, mother or sister,” he and Mary soon suspected that they represented a second species, and that this, not P. boisei, was the maker of the stone tools. Mary writes of this second smaller-toothed hominin that “he must be considered as the tool-maker of Bed I, in preference to [Paranthropus] boisei, who seems unlikely to have progressed beyond a tool using stage of development.” That more than one species of early human ancestors lived contemporaneously at that time was almost as controversial as the notion that they had been living in cooperative groups with home bases. It was only after their eldest son, Jonny, then just nineteen years old, found much more complete skull fragments, a mandible, some hand bones, and a complete foot nearby that they were able to announce their phenomenal discovery to the world.

  This second breakthrough find happened one day in 1960 only a hundred feet away from the enormous ongoing excavation of the P. boisei site. Jonny had noticed a strange-looking lower jaw that his father immediately recognised as the first sabre-toothed cat to be found at Olduvai. Because this was such a rare animal, Louis suggested that Jonny sieve the site to try to recover further pieces. Jonny didn’t find any more of the cat—the sieving team recovered a hominin tooth and toe bone instead. Before long, a handful of foot bones emerged from the excavation. These clearly belonged to one individual because Mary carefully extricated them from a small area of about one square foot. This momentous find was followed by several finger bones, a collar bone, and thin and fragile pieces of skull. Finally, the excavation yielded two rather large parietal bones (from the top of the skull) that lacked the sagittal crest that was such a prominent feature of P. boisei. Mary and Louis’s suspicions from the first excavation were confirmed—this was a much more humanlike creature than Dear Boy. Because the mandible, hand, and skull fragments belonged to a juvenile while the foot bones, clavicle, and radius were those of an adult, they were accorded two accession numbers—Olduvai Hominins (OH) 7 and 8.

  It is almost impossible to imagine how exciting this must have been for Louis and Mary, and also how difficult it would have been to put the new fossils they were finding in a proper context. The australopithecines from South Africa and the assortment of finds from Asia had not yet been grouped together as the single species H. erectus that we now believe they represent, and Mary and Louis had nothing local to compare their bones with. But these spectacular discoveries would completely change the picture of human evolution as it was then understood. East Africa went from being a complete nonentity palaeontologically speaking to becoming accepted as the very cradle of mankind just as Louis had always stubbornly insisted.

  In 1964, Louis and his colleagues Phillip Tobias and John Napier proposed that this new hominin from Olduvai was actually an early Homo, and the more complete juvenile mandible and the two pieces of skull from OH 7 were selected as the type specimen. This was hugely controversial because it was thought at that time that the first “human” attribute to evolve was the large brain. An obvious criterion to admit a fossil skull to the Homo genus was therefore a minimum brain capacity. In 1948, Sir Arthur Keith, one of the early giants in the field and a prominent anatomist of the British palaeoanthropological establishment, set this “cerebral rubicon” for the Homo line at an arbitrary 750 cubic centimetres. He arrived at this figure largely on the basis that it would exclude the South African australopithecines while including the material from Asia. This criterion is far too simplistic. For example, a brain size in and of itself tells us little; it is the size of the human brain relative to our bodies that makes us such a brainy species. We have since learned that brain enlargement was an attribute acquired quite late in human evolution as a result of other adaptations made possible by the move to bipedalit
y. But this knowledge would come from discoveries that would follow much later.

  Louis and his colleagues blasted the credibility of Keith’s definition of a cerebral rubicon for Homo. They were obliged to lower the cerebral rubicon to 600 cc to accommodate the new fossils within the Homo genus. And it is not surprising that this caused an uproar, particularly because Tobias estimated the cranial capacity of the juvenile skull to be 680 cc by reconstructing the skull from the two fragmentary parietal bones. (Tobias later revised this to 647 cc for the juvenile but extrapolated that the brain would have been 674 cc in adulthood). Never one to skirt controversy, Louis also tickled tempers with the choice of species name, habilis, which was suggested by Raymond Dart at Louis’s invitation. Louis, Phillip, and John expanded the definition of Homo to include bipedalism, a precision grip, and the lower brain-capacity threshold of 600 cc. Habilis (“handy man”) references the inference Louis made about his hominin’s ability to make stone tools based on the fact that the relatively complete hand bones showed a precision grip. The very real problem with this is that you cannot link bones and behaviour that we are no longer witness to—we can only infer who the maker of the tools was. They could have been made by other contemporary hominins. Nevertheless, the name H. habilis stuck, and OH 7, or Jonny’s Child, became the type specimen for the earliest species of Homo known at the time.

  * * *

  H. habilis SEEMED destined to continue on the controversial path that began with its naming. In addition to the disagreements on the basic attributes of Homo, there was a second level of dispute. During the rest of the 1960s and the 1970s, many additional specimens were found at both Olduvai Gorge and East Turkana that showed a large variation for a single species. This was especially contentious for the earliest specimens thought to date from around the two-million-year mark. At the centre of the dispute were two quite different-looking and well-preserved adult skulls from East Turkana found by members of Richard’s legendary field crew. These two fabulous fossils came in our windfall of finds that we enjoyed in the 1970s at Koobi Fora that mirrored the spate of good luck that followed Louis and Mary through the 1960s. Both have been attributed to H. habilis, but there were some disquieting differences between them. Everything was small about one of these skulls, KNM-ER 1813. It was lightly built, small brained, small toothed, and small faced, and had a very generalized morphology. The other, KNM-ER 1470, was larger brained and, like Kenyanthropus platyops, is remarkable for its flat face.