The Evolution of Who We Are. - Review - book review

Human Natures: Genes, Cultures, and the Human Prospect. By Paul R. Ehrlich. Island Press/Shearwater Books, Washington, D.C., 2000. ISBN 1-55963-779-X. 531 Pp. Hardcover, $29.95.

In writing Human Natures Paul Ehrlich set out to correct the erroneous assumption that all humans share a common value. That notion, he contends, "allows us to be painted in the popular mind as instinctively aggressive, greedy, selfish, duplicitous, sex-crazed, cruel, and generally brutish creatures with a veneer of social responsibility" While not denying Homo sapiens' capability to exhibit those behaviors, Ehrlich denies it as pre-programmed predilection. Human behavior is not a predetermined set of rules but a complex infrastructure, a "product of our histories, biological and cultural."

There has been much debate about the role genes play in human behavior, with many books and papers written in an attempt to understand to what extent human minds are "hard-wired." While respecting the gene's role in our evolutionary history, Ehrlich steadfastly disagrees with the idea of genes as a solitary explanation for our behavior. His argument, referred to as the "gene shortage" argument, is as follows: "Human beings have something on the order of 100,000 genes, and human brains have more than 1 trillion cells, with about 100-1,000 trillion connections between them. That's at least 1 billion synapses per gene, even if each and every gene did nothing but control the production of synapses (and it doesn't). Given that ratio, it would be quite a trick for genes typically to control more than the most general aspects of human behavior."

Ehrlich further says that even if genes did control all aspects of our behavior the resultant inflexibility would be crippling from an evolutionary position. What Ehrlich, among others, supports is the idea of gene/culture coevolution. Homo sapiens' survival is founded in their filling an evolutionary niche referred to as the cognitive niche. The cognitive niche gave our ancestors the ability to store information outside our genes. This socially transmitted information (behavior, beliefs, technology, art, et cetera) gave our ancestors an edge by allowing them to adapt to their environment by bypassing the traditional and slower genetic method. As Ehrlich sees it this nongenetic information increased the survival rate of our ancestors and created an evolutionary pressure for better cognition that was answered by both biology and culture.

The Great Leap Forward, an advance of Homo sapiens' technology accompanied by the introduction of art and massive population growth over a short time frame, has (at least) two competing theories. Ehrlich discusses both thoroughly but throws his support behind cultural evolution as the culprit. The competing theory is that our biological evolution brought on a complete change in brain structure, which gave Homo sapiens increased cognitive and/or lingual ability and that this led to the advancement seen in the Great Leap. The strongest argument against restructuring theory is the extremely short time frame, biologically speaking, for such a rapid and extensive change to have occurred. Definitive answers, however, are problematic because of the difficulty of tracing this type of information using the fossil record.

Whether it was a biological or cultural change that brought about the great advances in Homo sapiens technology may be unsettled, but the advancements of the past five hundred years surely point to our cultural evolutionary capabilities and show that our cultural evolution is outpacing our biological evolution. In some areas our cultural evolution overrides cornerstones of biological evolution. This opens a discussion about where our cultural evolution is raking us and what to do with that information. What, if anything, does our evolution tell us about ethics and morality? "Although the capacity to develop ethics is a product of biological evolution, there is nothing in that evolution that tells us what we should do ... the actual ethics, morals, and norms of society--the products of that ethical capacity--are overwhelmingly a result of cultural evolution within that society."

In the final two chapters Ehrlich steps away from the known and the scientific in exchange for a call to action, dividing the actions into the tactical and strategic. From the tactical Ehrlich says "perhaps the most important single tactical evolutionary lesson ... is that there is a dynamic relationship between Homo sapiens and the microorganisms that attack it." Ehrlich believes that the excessive use of antibiotics is creating a breeding ground for resistant strains of bacteria. He points to penicillin, once handed out indiscriminately to anyone with a sniffle, now being almost useless as an antibiotic. Our evolution has separated us so distinctly from our environment that we tend to forget that we are a part of the ecosystem. "Despite all the good things that have come out of human evolution, one thing is clear to me and to many of my colleagues who spend their time examining that predicament: our evolving human natures may be heading us toward the worst catastrophe in the history of Homo sapiens." The st eady demise of our ecosystems presents the greatest danger and is at the forefront of Ehrlich's strategic plan. To reverse this trend Ehrlich calls for a "conscious evolutionary process" whereby we would educate people in "understanding our evolutionary background and the biases it produces." Because our "cultural evolution, unlike biological evolution, is reversible," Ehrlich is hopeful that we may turn ourselves around.