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Human Natures: Genes, Cultures, and the Human Prospect

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Man's evolutional place in the world has been studied for centuries, through the sciences of anthropology, biology, geology, genetics, paleontology, and a host of others, and this book does a masterful job of bringing these together. What it does that is different, is describe the evolution of culture: politics, regligion, art, language, and other features of the upright-walking primate's life not so easily reduced to scientific explanation. Combining these two approaches to man's current predicament, Professor Ehrlich points aut that "the increasing ability to do things has outstripped the evolution of our ability to understand ... the full implications of what we are now doing," and with this approach, examines what is happening to us individually, to the human community, and to the environment in which we live. If you read one new book this year about man's place in the earth's past, present and future, this is the one.

I truly appreciated Paul Erlich's HUMAN NATURES, not only for the carefully studied exploration of humanity but also for his clarity. This intelligent, well-written discourse on human evolution gives a balanced view of our species, dispelling myths and explaining complexities, daring to explore controversial subjects. The topics covered - from the origins of language to racial equality to ethics, to name only a few - are well researched and comprehensive. In language and tone, HUMAN NATURES is neither overly technical nor simplistic; it is wonderfully readable without sacrificing depth.

If you have pondered the different roles of genes and the environment, if you are intrigued by the origin and development of cultures, if you encountered too many glib comments about "survival of the fittest" and want to understand the true depth of the concept as it applies to humans, read this book. You'll come away with so much more than you expected.

HUMAN NATURES, by Paul R. Ehrlich, at last gives laymen like me a readily accessible, comprehensive scientific insight into how the brains of not-so-simple primates evolved to make our "human natures" what we are today. Of more importance, Ehrlich gives us a superbly documented basis for addressing - perhaps even erasing - the genetic myths and phobias that have fueled ethnic prejudice, racism, sexism and all the other "isms" dividing us over the centuries. - Richard L. Graves, author of QUEENOF DIAMONDS, a mystery novel published Decmber 1 by XC Publishing, Tacoma, WA.

Paul Ehrlich weaves together evolutionary biology, ecology, anthropology, sociology, and common sense to explain the origins and behavior of human societies. In lucid, powerful, and often witty prose, Ehlich tackles some of the most fundamental questions pertaining to the role of genes and cultures in shaping who we are and how we behave. "Human Natures" is fun to read and rich in wisdom.

Paul Ehrlich does a great job of looking at why we humans are the way we are. He explodes a lot of the myths about genes being the sole determinate of agression, peacfulness, and many other things that we attribute to genes. Even after I took a break from reading I found myself thinking of the concepts that he states, and I couldn't wait to get back to the book. His views of sexuality are very thought provoking.

"Human Natures" is far and away the clearest, most comprehensive, and most compelling synthesis of what is known about the co-evolution of humans, their cultures, and the rest of nature currently available. The title subtly reflects the important distinction between human "nature" and human "natures" - the plural implying that our species has many and varied natures - not a single unitary nature. This pluralism is in stark contrast to the stilted and unrealistic assumptions about a singular human nature embodied in both the reductionist biological model and the conventional economic model. The biological reductionist idea that all human behavior can be reduced to a genetic basis is clearly insufficient in light of the massive importance of cultural evolution in shaping human behavior. Likewise, the all-knowing, perfectly rational economic utility or profit maximizer of the conventional economic model may be convenient for mathematical tractability, but it is so far from the reality of human natures that it is laughable. The only mystery is why, given what we know about human natures, more economists are not laughing. The case of Phineas Gage, described by Ehrlich in the book, serves to illustrate the size of the chasm between the conventional economic model and reality. Gage was a railroad worker who had a large portion of his frontal lobe removed when a 1.25 inch-thick tamping rod shot through his head in a freak railroad accident in 1848. Amazingly, Gage survived and was not even knocked unconscious by the accident. But he was a changed man. He had lost the part of the brain that we now know is dedicated to emotional responses. A surprising result was that while he could think, talk, and calculate perfectly well - he was completely "rational" - he simply could not make a decision. It turns out that rationality without emotions leads to swamping with details and the inability to make any decisions at all, even ones so trivial as what to eat for dinner. That emotions are necessary for decision making is an interesting part of real human natures, but is in direct contradiction to the conventional economic assumptions about decision-making, which considers emotions to be a hinderence to "rational" decision-making. But as Ehrlich points out: "Human emotional capacities evolved along with our cognitive capacities. Without the ability to respond to stimuli with appropriate emotions, critical decision making becomes impossible" (pp. 121-122). The challenge is to build economic models that incorporate the realities of human natures, rather than to assume them away. The weakest aspect of the book is the imbalance between its treatment of genetic and cultural evolution. While Ehrlich takes pains to acknowledge the large and growing importance of cultural evolution in shaping human natures, he gives very little space in the book to the details of how cultural evolution works and does not attempt to synthesize the research in this area in anything like the completeness with which he treats human genetic evolution. For example, he notes that cultural evolution has several unique characteristics relative to genetic evolution. Most importantly, learned behavior can be passed on through the culture to genetically unrelated individuals and changes in culture can occur with light speed relative to genetic evolution. But how does this work and what does this mean for human natures and for the future of our society? This and several other key questions about the details of the relationship between genetic and cultural evolution are hinted at in passing, but left largely unaddressed in the current volume. For example, conventional biological evolution theory is largely circular and descriptive, not predictive. It is one thing to describe how alligators evolved, but quite another to be able to predict the emergence of alligators. To do this one would need to know the underlying criteria for success in evolution that can be specified before the fact. From a predictive point of view, it doesn't help much to say that those individuals that reproduce best will survive, unless one can say why particular individuals will be able to reproduce better than others in particular situations. Most human evolutionary ecologists work on time scales that make this question moot, but it is essential for understanding cultural evolution, the results of which are observable in units of years rather than thousands of years. To use the evolutionary paradigm in predictive modeling, we require a quantitative measure of fitness (or more generally performance) that can be specified before the fact, in order to drive the selection process. Another important question has to do with the "reflexive" nature of cultural evolution - because we are capable of at least some degree of conceptualization and foresight, we can exert at least partial control over our own selection environment. The process then becomes one of conscious design and tinkering with the cultural evolutionary process rather than passive response to externally determined criteria. How does this process work and what are it's limits? Devising policy instruments and identifying incentives that can translate foresight into effective modifications of the short-run cultural evolutionary dynamics is the key research challenge. In cultural evolution, we have the unique potential to first envision our goals and then modify the selection criteria in order to achieve them. Ehrlich's book provides a solid basis for addressing these and countless other questions that are critical to understanding our human natures and how we can actively participate in changing them. Adequately understanding and controlling our complex human natures is essential to the continued survival of our so far exceptionally successful species.

A fascinating exploration of the human condition from one of the world's preeminent scientists, Human Natures traces the evolution of human behavior from the dawn of our species to our biotechnological present. Ehrlich has written an informative, readable account of human evolution revealing a complex interplay between genetic, environmental, and cultural forces. In the process he puts to rest a slew of popular misconceptions, from the myth of genetically homogenous races to the notion that genes determine individual behavior. Human natures, Ehrlich reveals, are as diverse as humanity itself.

This book is at once the most accessible and the most scholarly book available on human evolution. The first third is an incredibly clear synopsis of the current state of knowledge about hominid evolution, and this complex story is woven in exciting (no exaggeration) prose. This alone makes the book worth reading. But the way Ehrlich uses this biological background as a frame for exploring the much more rapid pace of cultural evolution makes this a new and penetrating examination of the human condition. Perhaps it is not surprising that it is an evolutionist who has put together the best synthesis of the relationship of biological and cultural factors, but I was surprised at the relative weight this author gave these themes. The importance of cultural evolution in determining the trajectory of human societies and, in fact, the fate of life on Earth is convincingly argued. At the same time, the critical biological "sideboards" that bound what is culturally possible is clearly articulated. This book supersedes the threadbare "nature vs. nurture" argument in a single bound, and it gives us a modern perspective that is more knowledgeable, more thought provoking, and it much more exciting.

And this is not one man's perspective. Ehrlich has drawn on an incredibly diverse group of scholars, as well as his own experiences at the forefront of research in evolution, ecology, and the environment. In diverse fields, he has read widely and discussed critical issues with the recognized experts. This depth of this research is conveyed in the extensive endnotes that take up more than a third of the printed pages. I read this book with two bookmarks, one for the text, the other tracking in the endnotes, which were every bit as readable and interesting as the main text. I've been through this book cover-to-cover once, and it is already one of the standard reference books on my shelf. It is a goldmine for anyone interested in what it is to be human.

According to Jared Diamond, "The one book to read on human evolution." Human Natures is clear, quite readable, and concise thus bringing a difficult subject into focus. Ehrlich disabused me of several notions that I had built up over many years of reading about evolution in various publications. No longer will I blame "genes" for everything that goes right and wrong in my life or the lives of those around me. Certainly, genes will still hold a prominent position in my understanding of human natures (plural, for there are many), but our environment will be moved up as at least an equal partner. Here is an example of his excellent style; Ehrlich writes (page 119 & 120):  "Despite the uncertainties, several general points with particular evolutionary relevance about the mechanisms of the human brain seem quite will established. In summary, they key points are as follows: 1. The brain is an organ that, like other organs, has evolved a structure that serves its various functions. 2. The brain can compensate for partial damage and, often, keep thinking. 3. The brain has many "programs"--connected sets of neurons--that have been built in over hundreds of millions of years by natural selection. 4. More recently evolved programs in the brain enable us to solve problems of relationships and causation that are difficult or impossible for other animals to solve. 5. Although selection has led to these capabilities by creation of appropriate genotypes, appropriate environments (both internal and external) are essential to produce the behavioral characteristics we observe. 6. Natural selection has designed the brain's programs to bias certain perceptions and behaviors. 7. Nonetheless, the genetic code does not build specific instructions into the brain's structure for dealing with every conceivable behavioral situation or even large numbers of them. 8. Natural selection has trouble doing just one thing at a time with respect to the brain, just as with other organs. It is unlikely, for example, that selection could produce a brain program that predisposes females to desire males with curly hair without changing other programs of the brain or, perhaps, other aspects of the human phenotype."

Ehrlich then goes on to explain all these concepts in detail with easily understood supporting evidence, arguments, and theories. From genes, to religion, to cultures, our complex human natures are unraveled and put before us to see and recognize as the wonder they are. Evolution of the human species is explained in the timeframe and the manner supported by the best scientific evidence of the day. Yet, the wonder and mystery of sentient beings is not in any way denigrated. This is definitely a book to read, and perhaps the only one those of us not in the sciences needs to read for some time to come.

Paul Ehrlich enters the lists of "nature vs nurture" by fulminating against the straw-man of "genetic determinism". One would have thought this joust would have been called for "time" by now. In his attempt to triumph over this rather ephemeral opponent, Ehrlich has performed a prodigious task. This well-written and comprehensive view of human evolution is a valuable resource. A massive footnotes and references collection grants this book value far above the narrative itself. Ehrlich, a practiced writer and researcher, brings many years of work and observations of the human condition to this massive overview. He strives to explain who we are and how we arrived at our current stature. He further warns that our lack of understanding of our backgrounds may threaten our future.

"Human nature" is often cited as a foundation for many behavioural traits. The fallacy of that moral expression is revealed in the variety of our habits. Ehrlich recognises that variation in his title and goes on to explain it in this book. While the genetic foundation of our behaviour is being solidly established by much field research, he ultimately concludes much of that basis is overriden by our cultural influences. Much of our confusion about "nature versus nurture", he contends, lies in the rapid pace of humanity. Compared to most other species, our mental development raced past the other animals - with language as the accelerator pedal. Since the genetic base for most traits is so slow and nearly muted, our development agriculture, religion and urban society virtually overwhelmed our "animal instincts". The prime example, of course, is the massive impact we have on our environment.

Ehrlich's key in assessing genetic versus cultural input lies [logically!] in the structure of the brain. When he wrote this book, the human genome was thought to be comprised of 100 000 genes. With that figure halved, he concludes the genome hasn't the power to command the billions of neurons with their trillions of connections that comprise the human brain. This "gene" shortage, he avers, suggests the genome hasn't the capacity to drive human behaviour to any significant degree. This rather simplisitic enumeration ignores the fact that the entire genome, whatever the number of genes, must be highly interactive in many areas of the body - the brain is simply another part of the mechanism. He is apparently unaware of the brain research showing how similar interactions have been mapped within the brain. Genes merely kickstart the process, they don't need to "control" our behaviour.

Ehrlich takes the usual swipes at Richard Dawkins as he builds his narrative. Like so many others, Ehrlich's reading of "The Selfish Gene" appears to have ceased at the title. To him, the "Great Leap Forward" of some fifty thousand years ago emancipated us from the shackles of our genetic heritage. With the development of language [which wouldn't have happened without a biologically endowed "voice box"], human cognition, hence behaviour, launched on a new course. Ehrlich asserts we've never looked back, but also warns our capabilities should be adapted to now look forward. Our abilities threaten the biosphere with an intensity and scope no other species possessed.

In his conclusion, the author nearly reverses all his prior narrative. He urges humanity to develop a better understanding of its place within nature. That, of course, means a full programme of understanding animal behaviour and the mechanisms animals and plants use to stay alive and reproduce. Our evolution, particularly the cultural input, has led us to believe we are distinct from Nature. Ehrlich recognises the dangers of such an attitude and urges us to overcome it. Although an excellent synthesis and supremely comprehensive, it's unfortunate that Ehrlich's prejudices blinded him to create a problem that doesn't exist. Nobody argues for "biological determinism" in an absolute sense - certainly not Dawkins. Where Ehrlich is correct is that we must increase our knowledge of how nature works and undertake the tasks needed to stop and reverse the spoilage under way.
[stephen a. haines - Ottawa, Canada]