The Sediments of Time

by Meave Leakey

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  THE LAST DECADE has involved many changes for me, both professional and personal. At home, our life has been enriched by three granddaughters who, like earlier generations of Leakeys, feel at home roaming for fossils in Turkana. Our old field team has retired, and a new guard of sharp-eyed fossil hunters has taken over—I no longer spend months out in the field with them but enjoy my all-too-short field days and the excitement when they find hominins. We have recently found some thrilling 3.5-million-year teeth in South Turkwell that again challenge our views about the diversity in early hominins. But not everything has been smooth. While the kidney I gave Richard all those years ago continues to work, his liver failed a few years ago. This involved a massive operation in the United States that gave him a new liver from a dear friend, and there was another arduous road to recovery afterwards. But recover he did, and through the building and running of the Turkana Basin Institute, Richard and I have once again shared many enjoyable discussions about human evolution with the new groups of researchers TBI has attracted.

  The questions have not changed that much. How many different evolutionary paths did early hominins take? How old is our own genus? When did hominins first begin to make stone tools? Can we map the evolution of our own species onto the descendants of the intrepid H. erectus in Africa? While these questions were already the subject of dinner conversations between Louis and Mary when Richard was a child, the thousands of fossils discovered in the last fifty-odd years make the discussions at our house all the more fun. But the last decade has also brought entirely new ways of exploring the information held in the fossils we find—micro-CT scanning, geometric analyses, ancient DNA, and even palaeoproteins.

  One of my personal highlights of 2018 occurred when, together with Fred Spoor and another long-term colleague, Isaiah Nengo, I was granted the privilege of scanning three fossils at the European Synchrotron Radiation Facility in Grenoble, France. The ESRF is the most intense source of synchrotron-generated light and produces X-rays a hundred billion times brighter than the standard ones used in hospitals. High-energy electrons race around a circular tunnel 844 metres in circumference. The brilliance and quality of the X-rays it produces are unparalleled, and they reveal the internal structure of matter in all its beauty and complexity.

  The synchrotron is in high demand, with time allocated on the basis of merit to only nine thousand scientists per year, and it was due to close that same year for upgrading. We were able to use this amazing technology on three of our fossil hominins, including Kyalo’s “very good hominin,” the erectus skull we discussed in chapter 17. These three specimens were chosen because they all have essential information in their inner ear that we had not been able to visualize using either medical-CT or “normal” micro-CT scanning. Thanks to this advanced technology, the analysis of these scans will likely tell us much that was previously unknowable from fossil evidence.

  All this new technology has significantly broadened the fields of research, amplified what we are able to glean from fragmentary evidence, and completely changed how we look for patterns and relations in the fossils. The field of genetics has already yielded some giant surprises, such as the existence of creatures whose ancient genomes were extracted from one small finger bone, but whose fossil faces remain undiscovered. In the fifty years that have gone by since I first went to Koobi Fora with Richard, we have learnt so much about our past. And yet this body of evidence remains but a small fraction of the past seven million years of our evolution. It is hard to conceive how much more will be discovered in the next half century or so.

  Epilogue

  As I approach the last few years of my seventh decade, I reflect on the immensely rich and action-packed life that I have had. I have been extremely fortunate to have witnessed firsthand many exciting discoveries and developments beyond my own specialty of human evolution. But I am constantly reminded that my children and grandchildren will live to see a very different world. The dizzying pace of new human inventions and explorations illustrates how humans have penetrated every corner of the planet with increasingly sophisticated technology. The speed with which this is happening is in stark contrast to the millions of years of slow human development that have been the focus of my life’s research.

  Evolution is constantly at work as features change or are co-opted for a different task at different times and rates. The configuration of our hands and feet, evolved for an arboreal life with grasping fingers and toes, adapted with relative ease to bipedality. Once freed from arboreal constraints, we became still more adept with our hands and acquired a wide range of motions and dexterity. These changes, when coupled with the selective pressures of a highly variable global climate, then paved the way for a strategy for procuring meat with relative ease, which fuelled our growing brains. This in turn pushed cooperation and communication further than the heights achieved in highly social, complex, and hierarchical primate societies. To these accomplishments, we recently added the great improvements to our health and comfort brought on by all our modern technology.

  It is to our primate ancestry that we owe the morphological and behavioural patterns that have thus far been to our immense benefit. But today, this heritage is a double-edged sword that could be our undoing. The unfortunate fact is that we are a greedy, acquisitive, and destructive species by nature—like many monkeys. Do not mistake me, for I have loved monkeys ever since my early days caring for them at the Tigoni Primate Research Centre. But when the baboons breach the barriers we have erected and get into our vegetable garden, the destruction is a sight to behold and lament. They invariably leave a trail of devastation behind them. Half-eaten carrots, tomatoes flung about, and maize and potato plants ripped ruthlessly from the ground testify more to a destructive intent and willful gratification than to a pattern of sustainable foraging. The monkeys are doing no more than what we humans are doing on a far grander scale all over the planet—with our depletion of the oceans through overfishing and a wanton disregard for the bycatch, our unchecked logging in forests, our clearing of huge tracts of land for agriculture and urban settlement, our ever-increasing pollution of the atmosphere with chemicals and carbon dioxide, and our profligate, wanton, and senseless overconsumption and dumping of single-use plastic that has resulted in a garbage patch in the Pacific Ocean twice the size of Texas. Microplastics now pollute our water system so completely that they have been found in the ice and snow in remote parts of the Arctic and at the bottom of the Mariana Trench, the deepest point of the ocean anywhere on earth.

  Our intelligence and our technology make us so much more efficient at pillaging resources. Where before there was a hand axe, now there is a chain saw or a bulldozer or even a mechanical digger. Where there was once a wooden canoe and a harpoon, now there is a trawler equipped with a sonar detector, refrigeration, and mechanised cranes. Our footprint on the planet is so large that geologists have now designated a new era, Anthropocene (“of man”), for our labours are now indelibly recorded in new layers of sediments and in the scars we have rendered in the earth’s surface. If we don’t survive, the rocks will bear witness to the havoc that we wrought long after we are gone.

  We have learned to cure many diseases that were previously often fatal, and we can overcome almost all of nature’s checks and balances to overpopulation. Many more children survive today than in the past, and our life expectancy has been significantly extended. As a consequence, our population numbers have soared and continue to do so. When Homo sapiens first left Africa, our numbers were extremely small. At the end of the Second World War, just after I was born and before antibiotics were generally available, the world’s population was 2.3 billion. In 1963, I was already concerned by the urban development that was gradually creeping over many wild areas I had known as a child in England. Today, the world population numbers more than 7.7 billion, and by 2050, it is predicted to rise to more than 9.8 billion. With this many humans on one planet, dangers not previously perceived as threats can become lethal
unless they are properly managed.

  On less sanguine days, I sometimes wonder if we merit the glorious and self-congratulatory name of H. sapiens (“wise man”). The remains of our extinct species might one day be discovered many million years hence and be given the alternative appellation of Homo stupidensis. For, as Richard remarked to me one evening early in 2008 as we discussed the tragic and worrying postelection violence and killings that were gripping Kenya at the time, “We are most certainly the only animal that makes conscious choices that are bad for our survival as a species!”

  Our brains are unquestionably the most exciting evolutionary adaptation of all time. But our cognitive superpower may be the making or the undoing of our species. Will our intelligence, this extraordinary and unique adaptation, ensure our survival? Or, like other extreme specializations (such as the exclusive grass-eating adaptations of the giant gelada baboons or the enormous antlers of the Irish elk), will our great intelligence ultimately drive us to extinction?

  As I ponder these unknowable questions about our future, I am sitting on the verandah of our comfortable cottage at TBI Ileret, which overlooks the lake and some of the richly fossiliferous sediments I know so well. The colours expose millions of years of history—from the deep-red beds full of fish to the paler fluvial deposits to the layers of volcanic ash spread over the landscape and the dark sandstones full of fossils laid down on the lakeshore. A chocolate streak darkens the middle of the lake beyond; the Omo River is flooding and bringing yet more sediments into this huge lake basin and continuing the cycle of sedimentation and fossilisation. I marvel once again at this incredible research locality with its unrivalled seven-million-year record documenting our ancestors’ evolution from the first bipeds to the technologic masters of the world. Beyond the lake are the Lapurr Hills, where even older sediments have preserved dinosaurs some seventy to ninety million years old. These hills are a constant reminder of our own fleeting presence on this planet.

  In the human evolution segment of our field schools, we demonstrate how extraordinarily brief this time is using an unfurled loo roll to represent the full span of our evolution. The earth’s formation resides on the first piece of loo paper five billion years ago. A full sixty sheets later, the first life appears in the oceans. Down the path of two hundred segments of loo paper, the students can then count out the history of early organisms, plants, reptiles, fish, mammals, and birds, with many blank sheets representing the sheer amount of time it all took for the families, genres, and species that are alive today to evolve from that first miraculous single-celled organism. In stark contrast, our entire human evolutionary history is crammed onto the two and a half centimetres of a single sheet of two-ply. Our own species appears one millimetre from the end of that final segment. I find this fact at once terribly humbling and immensely reassuring.

  Thanks to a career unearthing the fossils of many extinct creatures, I am aware that extinction is an inevitable part of life on the earth and that every species has a limited sojourn on this planet. By some estimates, 99.9 percent of all species that ever lived are now extinct. And there is every evidence to suggest that we humans are currently driving a new wave of extinction. But we are unique: no other species has the capacity to change the course of its longevity. Because we have the intelligence to understand the consequences of our actions and devise solutions to them, we alone can limit the damage that we cause and stop these negative trends. The very intelligence that has brought us so rapidly to this point could most certainly ensure a long and bright future if we choose.

  One of the hallmarks of humanity is our ability to combine our knowledge and expertise. It is our collective intelligence that has enabled us to land on the moon and send a rover to Mars. No single person has the expertise to do these things, but large teams of people specializing in different aspects of the project can. Our collective intelligence provides us with the knowledge to now plan for a secure future with fewer wars, a smaller carbon footprint, less exploitation of finite resources, and, above all, a more sustainable population. And where there is a will there is a way. Although we have a lamentable predilection to procrastinate and leave things to the eleventh hour, never before has there been such urgent need to take action to preserve our planet for the future.

  Acknowledgements

  I am immensely fortunate to have enjoyed the support of family, friends, and colleagues through the years, and those reading this memoir know who you are. My gratitude for all you have contributed to make my life and my work more fulfilling is profound.

  My greatest thanks must be to my family. Ours is a family business, and Richard, Louise, and Samira have been part of this journey at key steps of the way. Before them, Louis and Mary blazed a path of believing that humans originated in Africa. I owe a debt of gratitude to them too, and to my parents, my sister Judy, and my brother Roger. My aunt Margs, who looked after me during the war, was also a source of inspiration and long-forgotten facts about the early days.

  In writing about a time period of this span, there would be too many people to thank individually than could fit within the pages of a book. Our field is a collaborative one, and our knowledge is gleaned from small pieces of a large and connected puzzle.

  It goes without saying that the fossils are all important, and many people have worked as part of the Koobi Fora Research Project since its inception in 1968. Our original fossil searching team, all retired now, were with us as we broke ground, found new sites, built roads, camps, and airstrips, searched, sieved, excavated, and much, much more. Of this group, Kamoya Kimeu, Nzube Mutiwa, and Wambua Mangao deserve a special mention. During the writing process, these three also contributed many mirthful stories of the old days, some of which are recounted in these pages. They have been succeeded by a new generation of talented, dedicated individuals who have contributed much to field and labwork and must likewise be recognized, with special mention to Lawrence Nzuve, Cyprian Nyete, Benson Maina, and Martin Kirinya.

  A huge thank you to all the friends and colleagues who, over the years, have worked with me, both directly and indirectly, in pursuit of answers. These include more colleagues than I can name but who have nevertheless played significant roles at the National Museums of Kenya, as well as colleagues from institutions in Ethiopia, Tanzania, and South Africa. Among those who must be named in person are Zeray Alemseged, Chris Dean, Patrick Gathogo, Fred Grine, John Harris, Jean-Jacques Hublin, Christopher Kiarie, William Kimbel, Benson Kyongo, Marta Lahr, Fredrick Kyalo Manthi, Lawrence Martin, Emma Mbua, Ian McDougall, Yohannes Haile-Selassie, Fred Spoor, Alan Walker, and Carol Ward. Special thanks go to the great geologist Frank Brown, who sadly is no longer with us. Frank dedicated his life work to deciphering the geology of the Turkana Basin, and without his long-term collaboration all our finds would be meaningless. He was followed by other geologists and geophysicists, and among them Craig Feibel and Thure Cerling must be singled out for their signature contributions.

  We have been privileged to receive research funding from a variety of sources, and of these the National Geographic Society has played a key and enduring role throughout. With the inception of the Turkana Basin Institute, our research is at last on a more secure footing, and this is largely due to the support of Stony Brook University.

  For her part, Samira would like to thank many of the same circle of family, friends, and colleagues. In addition, thank you to my special friends for your encouragement, love, and laughter at all the necessary times, along with practical help in school runs, cooked meals, DIY, and other essential and much-appreciated support to keep my household ticking over. I am so lucky to have you in my life. My ex-husband supported my collaboration in this book in its earliest stages. Kika has been inspiration, support, and distraction to us both, and enriched the process with her boundless curiosity and questions.

  As to the actual writing process, an enormous debt of gratitude from us both goes to Marta Lahr, who encouraged and corrected us where we most needed it, and helped us in
so many ways. Without Gillian MacKenzie, our fabulous agent, the book would likely have forever remained a manuscript languishing on a hard drive. Thank you to the publishing house, Houghton Mifflin Harcourt, and to Bruce Nichols who understood exactly what we were trying to do and believed in our book. Special mention must go to our wonderful and tireless editor, Pilar Garcia-Brown, and to our sharp-eyed copyeditor, David Hough, who was able to add order to our unruly punctuation. We have been fortunate to work with Patricia Wynne, who drew the marvelous illustrations. Huge gratitude is also due to our cover designer, Martha Kennedy, along with our production team: Kimberly Kiefer, Heather Tamarkin, Chris Granniss, Chloe Foster, Katie Kimmerer, Laura Brady. Last but not least, we acknowledge the tireless efforts of our publicist, Michelle Triant, and our marketing expert, Liz Anderson. It goes without saying that any remaining errors are all our own.

  Sources