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Human Nature Review 2002 Volume 2: 210-212 ( 5 June )
URL of this document http://human-nature.com/nibbs/02/petto.html
What It Means to be 98% Chimpanzee: Apes, People, and Their Genes
by Jonathan Marks, Berkeley
(CA): University of California Press, 2002
Reviewed by Andrew J. Petto*, Ph.D., Division of Liberal Arts, University of the Arts, 320 S Broad St., Philadelphia PA 19102-4994 USA.
Nothing. And everything. That is Jonathan Marks's conclusion in this wide-ranging book about the understanding and misunderstandings that genetics, and particularly "molecular anthropology", have generated about what it means to be human. Somewhat more eloquently, Marks writes:
There is consequently no guarantee, short of detailed physiological and genetic data and analyses, that anything chimpanzees do is directly relevant to understanding anything that humans do. Since they have been different species for several million years, anything that chimpanzees do may be either (1) an element shared with human nature; or (2) an ancient element of human nature now lost by humans; or (3) an evolved elements of chimpanzee nature, never possessed by human ancestors (pp. 160-1).
Make no mistake: those detailed physiological and genetic analyses are barely begun. In other words, we may share over 98% of our DNA with chimpanzees - that oft-quoted value, Marks points out, is based on an assessment of significantly less than the complete human (or chimp) genome - but what a difference that 2% can make: not even a casual observer would mistake a chimp for a human. What this small difference means depends on what we wish to know.
This book is more than a long argument about the technical precision of various genetic and biochemical methods, however. It is about what we make of them. Long before the 98% figure burst forth into the public discourse, scientists and nonscientists alike were convinced that the African apes were our closest biological relatives. Every relevant discipline - comparative anatomy, palaeontology, embryology, psychology, behavioural ecology, comparative physiology, and so on - produced the same conclusion. In one sense, the molecular studies only confirmed what we already knew, as they should.
However, in another sense, the widespread use of this figure is misleading, Marks argues, because its apparent precision generates a false sense of scientific certainty - not so much in the great genetic similarity that it confirms between closely related species, but in the inference that this figure somehow "explains" things. What things could it explain? Suggestions range from promiscuity to aggression to homosexuality to any of a wide variety of interesting conditions that have so far only the most tenuous connection to specific sequences of DNA contained in the individuals who express them. There is a long, long chain of inference here, and for years Marks has consistently been calling scientists and science popularisers to task for their overgeneralizations of genetics research to address a wide variety of interesting social, legal, and technical issues: everything from racial studies, to animal rights, to creationism, to cultural hegemony and colonialism. And he tackles each of these in turn with relish in What It Means to by 98% Chimpanzee.
Despite the apparent precision of scientific studies and the authority with which their results are reported, most violate what Marks calls "a simple rule of molecular anthropology: Genetic conclusions require genetic data" (p. 114, emphasis in the original). This is a theme that Marks has been pursuing since the 1980s - any genetic explanation for an observed difference between populations (or even species) "requires more than just observing the difference to be consistent, It requires presumably genetic data" (p. 91).
But this is more than just an account of scientists' behaving badly (or even of bureaucrats and ideologues misusing science). It is also a call for the maturation of a field that calls itself "molecular anthropology" - to be as much anthropological as molecular. Or, as Marks put it, "What would constitute an 'anthropological biochemistry' if you didn't need to know any biochemistry to do it?" (p. 3). In other words, genetic studies of human populations and variations within and among human populations will always find biological (and biochemical) variation. The transformation of these observations into meaningful data - what Marks calls the transformation from "information into knowledge" (p. 78), which is the essence of scientific and scholarly practice - requires a context. In scientific studies, of course, this context is provided by the guiding theories in the discipline and the hypotheses that these theories generate. They are the questions that we are trying to answer by studying data on human variation.
One of the big problems with contemporary pronouncements about the "genetic basis for" any variety of human variations (and as "explanations" for differences among groups) is that the context used to generate those questions derives from the old, discarded typological views of human classification - views increasingly rejected by anthropologists beginning in the 1940s when anthropology began to acknowledge that human populations are not "naturally packaged into discrete groups" (p. 73). Molecular (or any) studies based on these old notions that human variation fits into several types with fixed biogeographic boundaries ignore contemporary anthropological theory - and reality. This would be comparable to initiating a new "genetics" research project based only on methods and practice from the 1940s, before the discovery of the structure of DNA.
True to Marks's writing for general audiences, the style is frank and often blunt, but it cuts right to the point. Marks wants there to be no mistake about his critique of how we - even some researchers - make more of genetic differences and similarities than the data can bear. I admit to being a real fan of Marks's work in this regard. Overall, he makes his points cleanly and explains them well. There are only a few exceptions - a tendency to insert familial anecdotes as analogies to phylogenetic relations and a couple of attempts at explaining why paraphyly in modern Homo sapiens populations destines most tripartite racial analyses to utter failure (which finally is cleared up on page 134; some will disagree that contemporary African populations subsume the gene pools of European and Asian branches of the species, even though ancestral African populations certainly did). However, in the context of the whole work, these are minor quibbles.
In a sense, What It Means to be 98% Chimpanzee is a reality check. It asks the important questions behind the hype of the Human Genome Project and the continuing stream of new genetic "breakthroughs" reported in the media. These questions are not just the rumblings of some anthropological curmudgeon; they resonate in the minds of ordinary citizens. Early in 2002, one of the students in my Human Variation class grappled in her journal with the main theme that would later appear in Marks's book:
[T]hey announced in late June of last year that they had completed the first draft [of the entire human genome]. Scientists are calling this one of the biggest milestones in history. Why? How will our lives change now that we know what's in our genes?
How, indeed? The answer, Marks tells us, is not in our genes, but in how we make sense of the genetic data about human variation. And that needs contemporary anthropology to provide a context.
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© Andrew J. Petto.
* Andrew Petto is a bioanthropologist specialising in the study of nonhuman primates. He is Associate Professor of Liberal Arts at the University of the Arts, Philadelphia PA, and teaches courses in general biology, human variation, pseudoscience, and anatomy, He edits Reports of the National Center for Science Education and is the co-editor of Scientists Confront Creationism, revised edition, to be published in 2003 by W. W. Norton Co.
Petto, A. J. (2002). Review of What It Means to be 98% Chimpanzee: Apes, People, and Their Genes by Jonathan Marks. Human Nature Review. 2: 210-212.