Report on Spencer Wells’ The Journey of Man: A Genetic Odyssey

            Spencer Wells takes a very technical and academic subject and makes it not only understandable but interesting and enjoyable in his The Journey of Man: A Genetic Odyssey. As Wells is not simply an author explaining the work of others but a leading population geneticist his writing is authoritative and conveys his “insider’s” sense of curiosity and excitement. Journey describes the evolutionary history of man as well as man’s movement from origin in Africa to the rest of the globe and particularly how genetic science documents the journey. Additionally he describes the interrelationship between genetic science, physical evidence, and linguistic research in determining the paths of the journey as well as solving a variety of anthropological mysteries.

            There are three specific aspects of interest in Journey which relate precisely to various topics in human anthropology. Wells provides a thorough and entertaining explanation of evolutionary fact and theory, including biographical sketches of the significant historical figures. He also guides the reader through an introduction of genetics and genomics and their importance in investigative research. Finally he places the historical journey of man in context with current issues of human biological diversity.

            Wells begins Journey with a review of the major contributors to evolutionary theory, including Charles Darwin, Thomas Huxley and Louis Agassiz. He explains the early theories that developed in the latter part of the nineteenth century as well as earlier contributions by Linnaeus. The concepts of natural selection, nature versus nurture, and survival of the fittest are described, and the social importance of these concepts at the time. The early evolutionary theories developed as a result of what could be observed, and what could explain the obvious diversity. While evolutionary theory was clearly within the domain of biologists, naturalists and philosophers, there were and are consequences in other areas as well.  He notes the development of the Eugenics theory and the writings of Carleton Coon, who “advanced the theory that there are five distinct human subspecies” which give rise to assertions of “genetic superiority” (9). Wells cites several historical examples where the idea of genetic superiority, and therefore genetic inferiority provided the “reason” for a variety of horrific events, from forced sterilization to the “systematic extermination” practiced by the Nazis (12). Later in the text Wells documents how Coon’s theories have been completely and scientifically refuted.

            As the title would suggest, a fundamental knowledge of genetics and genomics is required to understand the text. Wells explains that “genetic variation was critical to the study of human diversity because it is genetic change that actually produces evolution” (14). On the fundamental level Wells covers “basic population genetics” including the three theoretical concepts of mutation, selection, and genetic drift (18-19). Examples of each concept are provided and Wells also covers early genetic work using blood samples to determine genetic variations. With this background Wells describes the discovery and development of DNA sequencing which “set off a revolution in biology that has continued to this day” (26).

Wells explains in detail the discovery of the fact that certain genetic sequences will be consistently be passed either through the mother or the father, and describes the revolutionary discovery 1987 when examination of a mitochondrial DNA segment established that it could be traced to a common “Eve” living two hundred thousand years ago (30). Similarly a common male ancestor was also traced back, however only as far back as sixty thousand years ago (54). Wells is able to explain the difference in the “genetic history” and states that “beyond placing all modern humans in Africa within the past 200,000 thousand years, are therefore disproving the multiregional model of human evolution favored by Coon and others, the dates have very little significance” (54). What is significant is the ability to determine a variety of evolutionary and migratory patterns through DNA studies. There are numerous examples throughout the book, including how DNA mapping can yield surprising results, such as a man “hoping for a genetic link to the Zulus of southern Africa” had instead a classic European marker, likely placed in his “family tree” during an ancestor’s life in slavery (184-185).

            There are numerous examples of biological human diversity described and explained in Journey, many of which have existed “unadulterated” due to remote geographical areas. However, fewer and fewer areas are inaccessible. The example given by Wells are the Yagnob people of Tajikistan, people he personally studied as they were “a direct link back to the days of the Silk Road” and were the last speakers of a language that was a “1,500 year old artifact” (186). Reaching their village was only recently possible due to the breakdown of the Soviet Union, as well as the remote location. For many reasons, including earthquake and drought, they have abandoned their village and moved into formerly remote cities. Wells states “the Yagnob are not an unusual case, in fact, quite the opposite” (187). While biological diversity can be protected “in the wild” with specific habitats, human biological diversity will slowly disappear into “the global melting pot” (191). Languages are rapidly disappearing and “the dynamics of language extinction indicate that human mixing is now accelerating” (191). This is not something to be feared or something that should be prevented. It is obviously a natural part of man’s evolution. As the “melting pot” is inevitable, the origin and journey of man is all that more important to study and understand.

References

Wells, Spencer. The Journey of Man: A Genetic Odyssey. Princeton: Princeton University Press, 2002.