Book review of Origins by Richard Leakey, and Roger Lewin, Doubleday, 1992

Richard Leakey is a world renowned paleoanthropologist (son of Louis and Mary Leakey) and Roger Lewin is the author of several prize-winning science books. In 1977, they co-authored Origins, and return to update their earlier conclusions and add new information.

In 1984, Leakey and his crew discovered the "Turkana Boy" on the shores of Lake Turkana in Kenya. This l.5 million year old skeleton is recognized as one of the most significant discoveries of all time. To quote from the book: "Homo erectus, the Turkana boy's species, represented a pivotal point in human evolution. More or less everything that preceded erectus was distinctly apelike in important respects: in some of the anatomy, life history, and behavior. And everything that followed erectus was distinctly humanlike. The Turkana boy had been part of a major shift in human evolution, one in which the seeds of the humanness we feel within us today were firmly planted..."

The book is largely a narrative of this discovery and of how he went on to explore the current theories of how humankind evolved. He discusses the methods used by scientists of different disciplines, and incorporates ideas from philosophy, anthropology, molecular biology, and linguistics in his investigation of how humankind acquired the qualities that make us human. It is also something of a basic text on evolution.

Richard Leakey is now the head of the Kenya Wildlife Service, which places his life in constant jeopardy. That, plus his deteriorating health, both of which he is constantly aware, could make this his last work. In that sense, this could well be his testament.

The following is the thesis of the book: "...I believe that the qualities of humanness--consciousness, compassion, morality, language--arose gradually in our history, products of the evolutionary process that shaped our species. These qualities are, of course, most appropriate in the interactions among individual humans; they are the threads that hold the social fabric together. But, together with our creative intellect, they form part of our perception of the rest of the world of nature. I am not suggesting, as some people do, that every species of plant or animal has the same rights in society as humans. It is correct that we recognize the special value of a human life. But it is also correct that we recognize the place in nature of the human species, Homo sapiens, as one species among many. This is the true insight into our origins."

Origins Reconsidered

This is the title of the last chapter. It is a summary of the meaning of the discovery of the Turkana boy and Leakey's subsequent investigations and resultant discoveries.

The authors begin: "The urge to know is a defining feature of humanity: to know about the past; to understand the present; to glimpse what the future may hold...Human consciousness...is resourceful at creating explanations where none naturally exist."

Paleoanthropology is one of the few sciences which can give answers. The authors have more information since writing the first ORIGINS, and they can now present new arguments to the several interpretations of the origins and future of humankind. These interpretations are grouped under the headings of Inevitability, The Gap, and The Sixth Extinction.

Inevitability

Inevitability is the belief that the arrival of Homo sapiens was predestined: since we are here it must be for some purpose, otherwise it is by chance, and for many people such a conclusion is unacceptable. This has been expressed mainly in three ways:

First, because of the special qualities of Homo sapiens we are here by design, or, the fact that something works well implies that it was designed to be the way it is.

Second is the Anthropic Principle, the view that the universe is the way it is because it could be no other way. Since the laws of the universe operate within tight margins and we are here to observe them, the fundamental laws must be as they are.

That the unfolding of life on earth has followed a path of progress and predictability is the third belief. Evolution is viewed as constantly striving for improvement, fashioning an ever more efficient and successful organism, and if the process were set back to the beginning and run again, much the same pattern would result. The adoption of upright walking, the modification of the dentition, the origin of the expanded brain and the ability to expand the range, the emergence of complex spoken language--each can be seen as part of a cumulative and predictable march toward the present Homo sapiens.

The authors respond to these three arguments by citing several factors which must be considered. The first are the several climatic and environmental changes which triggered evolutionary innovations. One was the drastic global cooling around 2.6 million years ago which correlates with the origin of a new species and the evolution of the enlarged brain, the beginning of Homo. Had this cooling not occurred with the resultant ecological modifications, "...perhaps Homo would not have appeared then, perhaps not at all."

Then there are the environmental and climatic changes associated with the formation of the Great Rift Valley, some ten million years ago and onward. Those highland, mosaic environments were important in the origin of the hominids and had there been no such tectonic events in East Africa at that time, leaving the forests intact, "...perhaps hominids would not have evolved then, perhaps not at all."

Another factor is the mass extinctions which devastated so many species. In these events, many of the normal rules of biology are briefly suspended, principally those relating to everyday competition and survival; and geographic distribution, body size, and plain luck determine survival, rather than inherent superiority or adaptation. "Had that primitive primate been less lucky at the Cretaceous extinction, there is no reason to expect that animals like primates would ever have evolved again, no prosimians, no monkeys, no apes--no humans."

The authors explain further that just because a particular species has unlimited evolutionary opportunities ahead of it, potential changes are to some degree constrained by its existing anatomical architecture and its historical heritage. What happens is a contingent fact of history, not the march down a predestined evolutionary path; Homo sapiens was one of a range of possibilities, not an inevitability. The important message that comes to us from the fossil record is that it makes no difference to reason that if the circumstances been only slightly different in the history of life, that we would be or would not be. What is significant is to realize that our being here was by no means inevitable, no matter how our very humanness rails against the notion.

The Gap

The Gap is the notion that because of the special characteristics of humankind, we are set apart from the rest of the world. Among these are our technological skills, our ability to modify the environment, our cultures, our aesthetic sensitivities, and ethical sensibilities. One notable distinction has been the elaboration of many mythologies and religions to contain and explain the world. This is undeniably unique to the human species.

However, Mr. Leakey believes that standards of ethics and morality could be derived in the absence of religion. Since altruism is part of the behavior of social animals, it can be expected to develop much further in intelligent and intensely social animals like our human ancestors. Therefore, such standards are an inevitable, and predictable, product of gradual human evolution. This is the humanists' position.

Culture also sets humankind apart. We are a cultural creature unmatched by any other species. This is a dimension of behavior which essentially creates another world, one whose ideas and knowledge may be constantly reshaped and transmitted from one generation to the next. We all take part in a cumulative expression of our species. Our present culture depends in a very direct way on what was done many generations back, and we are the beneficiaries of our distant ancestors in a way not experienced by any other species.

The authors trace the development of civilization beginning with the 100,000 years as hunters and gatherers, small bands who were part of larger social and political alliances. Material worlds were limited, but their mythic worlds were rich, passed from generation to generation. There was a change between twenty thousand and ten thousand years ago when humankind began to organize their practical lives differently, exploiting food resources in a way that allowed less mobility, more stability, perhaps more possessions. Finally, from ten thousand years onward, food production became more common. Villages sprang up, small towns, cities, city-states, and eventually nation-states arose. Civilization had arrived, founded on generations of slow cultural changes, with a range of practical, intellectual, and spiritual possibilities which is the ultimate expression of the power of culture. Surely it sets us apart from the rest of the species in the world.

The authors seem to be answering the question of the Gap in positive terms, citing reasons why it exists. But they finish their examination of The Gap with the conclusion that this gap is more an illusion, an accident of history. We only feel special and separate because no species comes close to our accomplishments. One of the most important lessons learned by looking at the fossil record is to recognize that there is an unbroken genetic link that binds humankind to the nonhuman world of nature. Consciousness, compassion, morality, and language did not begin with the origin of Homo sapiens; our ancestors were more than erect apes. The emergence was gradual; other species do indeed match up to us to some degree. That they are no longer here is a contingent fact of history. The Gap is closed.

The Sixth Extinction

This is the third of Mr. Leakey's concerns. He notes that since the origin of complex forms of life on Earth, there have been five mass extinctions and a number of smaller events. This represents a periodicity of twenty six million years during which the number of living species collapsed catastrophically. (The Permian event wiped out 96 percent of all species.) Each mass extinction changed the Earth's biota on a grand scale.

The rapid recoveries from these periodic mass extinctions characterize Earth history. After each collapse, survivors diversified by exploiting the available ecological opportunities thoroughly and swiftly. Over a few tens of millions of years the overall diversity often reached close to or even exceeded the levels before the previous mass extinction. Following the most recent Cretaceous extinction (6.5 million years ago), the level of diversity was higher than at any previous time. Thus, biota change is repeated time and time again.

We are now in the midst of the Sixth Extinction with the loss of 50 percent of species. There have not been any catastrophic impacts from asteroids this time, no massive chains of volcanic eruption, no global disaster of natural origin. Instead there is the inexorable growth of human populations, enveloping and destroying the habitat of the rest of the world's organisms. The number of extant species is collapsing, and we are the agents of their demise.

The authors draw the readers attention to the lessons from the fossil record. For the most part, species do not last very long; invertebrate species on average have a longevity of five to ten million years and vertebrates about two million years. As a result, more than 99 percent of all species that have ever lived are now extinct. Species go extinct not because they are in some way inferior, but because they succumb to the vagaries of the processes of extinction.

They conclude that it is culture, transforming and enriching the life of Homo sapiens, which may block further evolution of humankind. Evolutionary change by natural selection proceeds by the differential survival of genetically favored individuals. By making survival subject to many nongenetic factors, culture effectively eliminates that process. "Further evolution is probably at an end unless there is genetic intervention by new technology or deliberate breeding programs over many thousands of years--both of which options properly ring ethical alarm bells in our society."

But the notion of further evolution of Homo sapiens should be placed in a larger time perspective. In our recent history, two intellectual revolutions shook humanity's perception of itself in the scheme of things. The first was the sixteenth-century Copernican revolution which dislodged the Earth from the center of the visible universe to the position of one small planet among others, circling a small sun. The second was the nineteenth-century Darwinian revolution placing humans in the same biological category as the Earth's other species. Added recently to these two insults there is a third: the scale of the universe itself.

This new scale describes a universe some twenty billion light years across, unimaginably vast, with our solar system and its host galaxy, the Milky Way, an insignificant corner of infinite time and space. It is calculated that our own sun will produce heat and light sufficient to sustain life on Earth for another five or ten billion years. These figures challenge not only the mind in its attempt to comprehend them, but also the strength of the human spirit in its perception of itself. However, long before the sun's energy is finally spent, it is a certain guess that Homo sapiens will no longer exist, another extinct species in Earth's history of biotic collapse and recovery.

The authors remind us that we humans, with our intelligence, our technology, and our power, are the stewards of planet Earth and that its future is in our hands. But because we find it impossible to imagine a time when we will no longer exist, we naturally equate the future of Homo sapiens with the future of the planet. However, the logic of the fossil record, and the logic of a true understanding of Homo sapiens as one species among many, forces us to accept that this is not the case. We are not stewards of the Earth, forever and a day. We are merely short-term tenants, and pretty unruly and destructive ones at that.

Mr. Leakey concludes by reminding us that "...it matters not at all that other species do not possess a degree of consciousness like ours, do not experience feelings in the way we do. They are part of our world; we are part of theirs. Our greater intellect may confer on us an enhanced ability to exploit the natural resources of the world. But--and I feel this very strongly--it also lays on us an enhanced responsibility to husband those resources carefully, to be sensitive to the knowledge that a species, once extinct, is destroyed forever. By impoverishing the environment, we impoverish our own lives, in this short-term tenancy we have on planet earth."

--Bob Green