Christopher Seddon - Humans: from the beginning: From the first apes to the first cities

This book does what it says on the cover: it is a history of the human world from the time of the first apes to the time of the first cities. It is intended for anybody who is interested in the origins of the human species and how we subsequently went on to populate the world, discover agriculture and eventually build cities. This vast span of time covers all but that tenth of one percent of the human story that we know as recorded history. The reader will learn that todays complex societies are fundamentally no different to those of later prehistory; and that their ultimate origins go back millions of years. Many contemporary concerns also have deep roots: climate change has long played a pivotal role in our affairs andthose of our ancestors. Habitat destruction, loss of biodiversity and failed states are also nothing new.

Within my lifetime, our knowledge the distant past has been greatly increased by modern science. The invention of radiocarbon dating in the1950s essentially rewrote the prehistory of Europe. More recently, genetic techniques have demonstrated our close evolutionary relationship to chimpanzees and the recent African origin of modern humans. Much vital albeit less headline-making work is carried out using methods that would not be practical without computers. We should remember, though, that the study of prehistory is a fairly recent discipline. That there was even such a thing as prehistory was not widely recognised until Darwins time.

Human evolution and prehistory is now a fast-moving and dynamic field. As recently as 2009, when I commenced work on this book, there was still no strong evidence that modern humans had interbred with Neanderthals. The enigmatic Denisovans an archaic human species that apparently also interbred with modern humans had yet to be discovered, as had Australopithecus sediba, a South African species that might be the direct ancestor of the first humans. Many long-established scholarly paradigms have been called into question by recent findings. Such discoveries are widely reported in the media, reflecting the level of public interest in our origins and our past.

The field is of course well-covered by a wide range of books covering every major topic and aimed at specialists, non-specialists and general readers alike. What does not exist is a single volume, single author book that covers the whole story: human evolution from the first apes to modern humans; the dispersal of modern humans from Africa to every habitable continent; the adoption of agriculture in many parts of the world at the end of the last Ice Age; and finally the appearance of state-level societies not too dissimilar to the modern nation state. In short, a one-stop guide to prehistory; a book not just for students and specialists but also for those wishing to know more about the subject but not quite knowing where to start.

It is this gap that I have set out to address with my book. To write such a book was certainly not easy: in addition to the sheer volume of material, the number of academic disciplines involved is considerable and includes anthropology, archaeology, sociology, evolutionary biology, zoology, botany, genetics, geography, climatology, geology and physics. I have tried to make it accessible to all while maintaining the fullest standards of academic rigour. Above all I have tried to avoid writing a textbook. In a textbook, a chapter is formally structured, with overviews, summaries and conclusions. Just as Stephen Hawking was advised that equations would hurt sales of his A Brief History of Time, I felt that such an approach would reduce the appeal of my book to the general reader. My priority has been to present the facts in the context of a readable, flowing narrative.

What is a hominin?

The characters in our story are a group of two-legged apes known as the hominins, of which modern humans (Homo sapiens) are but the most recent. The hominin line came into existence in Africa around five to seven million years ago, when our ancestors diverged from those of our closest living ape relatives, the chimpanzees. Today, we are the only hominin species in existence, but this is actually unusual. For most of the period with which we are concerned, there were several hominin species in existence in various places at the same time. Not all of these hominins were our direct ancestors; many were evolutionary cul-de-sacs that died out completely. Rather than an orderly procession of ever-more advanced species, leading inexorably towards Homo sapiens, the hominin family tree has been likened to a tangled bush.

The exact number of hominin species within this bush remains uncertain. The first and perhaps most obvious reason is that many hominin species may remain undiscovered to this day, even assuming that any of their fossilised remains have survived to be discovered. The second, less obvious, reason is that palaeoanthropologists frequently disagree on just how many distinct species are represented by the fossil record. The two rival schools of thought are known informally as the Lumpers and the Splitters: the Lumpers try shoehorn as many fossils into a single species, while the Splitters need very little excuse to proclaim new species or even new genera for each new fossil discovery.

What is becoming clear is that there were three main phases in the evolution of the hominins after they diverged from chimpanzees. The hominins from the earliest phase lasting from around seven up to 4.2 million years ago were dual-purpose apes with brains no larger than those of chimpanzees, and adaptations for both tree-climbing and two-legged walking. We are fortunate in that we have a remarkably-complete 4.4 million-year-old hominin skeleton belonging to the species Ardipithecus ramidus. The skeleton, popularly known as Ardi, was discovered in Ethiopia in 1994, and has greatly increased our knowledge of this period of hominin evolution. Ardi retained tree-climbing adaptations including an opposable big toe and thumb; later hominins (including ourselves) retained only the opposable thumb. We also have remains of an earlier Ardipithecus species, Ardipithecus kadabba, which lived from 5.8 to 5.2 million years ago; and two even earlier species, Orrorin tugenensis and Sahelanthropus tchadensis, which may push the hominin fossil record right back to the split with chimpanzees.

The hominins from the second phase lasting from around 4.2 to 2.0 million years ago are known as australopithecines. Their brains were again no larger than those of chimpanzees, and they probably still spent time in the trees, but they were now better adapted to walking upright. The opposable big toe gave way to the modern in-line big toe; the foot was arched; and there were other adaptations to the striding gait of a modern human. The australopithecines were widely distributed in Africa, though lumpers and splitters argue over just how many species there were. It is generally accepted that the first humans evolved from australopithecines, though from which species and where remains disputed. The australopithecines probably made and used stone tools, though the evidence is rather limited.