Throwing out the mismatch baby with the paleo-bathwater
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From the book : Evolutionary Psychology 11 issue 1 : 263-269.
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| Publié par | evolutionary-psychology |
| Publié le | 01 janvier 2013 |
| Nombre de lectures | 6 |
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En savoir + Paternité, pas d'utilisation commerciale, partage des conditions initiales à l'identique
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| Langue | English |
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Evolutionary Psychology
www.epjournal.net–2013. 11(1): 263269
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Book Review
Throwing Out the Mismatch Baby with the PaleoBathwater
A review of Marlene Zuk,Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live. W. W. Norton & Company: NY. 2013. 255 pp., US $27.95, ISBN #978 0393081374 (hardcover).
Robert O. Deaner, Department of Psychology, Grand Valley State University, Allendale, MI USA. Email: deanerr@gvsu.edu(corresponding author)
Benjamin M. Winegard, Department of Psychological Sciences, University of Missouri, Columbia, MO USA. Email:8vmwmab@.milsois.iruudeb
In many respects, our lives today are vastly different than anything our ancestors experienced. Think antibiotics, laser surgery, social networking, GPS mapping, jet airplanes, baby monitors, drone strikes, supermarkets, and ultraproductive farms requiring almost no manual labor. The scientific knowledge and technological systems that brought such changes have also yielded increasingly detailed information about our evolutionary history: We know that our lives today are not merely much different from those of our great grandparents; they are extraordinarily, almost unimaginably, different from those of the huntergatherers living in the paleolithic. If one takes natural selection seriously, these facts suggest that our bodies and brains may be largely adapted to deal with historical challenges that differ substantially from contemporary ones. This mismatch perspective serves as an indispensable lever for scholars aiming to illuminate human nature and for practitioners and policy makers attempting to improve lives. In the new book,Paleofantasy, Marlene Zuk offers a sharp rebuke to mismatch proponents, especially those holding to singular views of human lifestyles in the paleolithic. Zuk is no antievolutionist: She is a distinguished evolutionary biologist who has made seminal contributions, especially in the field of sexual selection. The arguments inPaleofantasydeserve careful consideration, but they ultimately fail to support the book’s thesis, at least the strong version we will consider here, namely that a mismatch perspective is unproductive.
Throwing out the mismatch baby with the paleobathwater
No Mismatches Zuk is initially skeptical of the mismatch perspective because all species, including humans, are adapted to past environments, not their current ones, meaning that no species or population can be said to be mismatched to a greater degree than another. But this claim is false. Simply because all species might be somewhat mismatched does not mean that all are equally mismatched. Imagine two islands colonized by a new predator for the first time. If a prey species on one island has faced a similar predator for thousands of generations, it would likely fare much better than would a similar prey species residing on an island that never faced a similar predator. It therefore makes sense to say the latter species is unprepared or mismatched, and it is conceivable that it could remain mismatched for many generations.Zuk eventually concedes the possibility of mismatches. But she then objects to the way that scholars of human evolution invoke the concept using terms such as the EEA (Environment of Evolutionary Adaptiveness; Tooby and Cosmides, 1992) and the ARE (Adaptively Relevant Environment; Irons, 1998). Zuk considers these too blunt and believes the EEA especially invites simplistic thinking, such as the fallacy that all human adaptations arose at a specific time and place. Although Zuk acknowledges that these terms can and sometimes are used appropriately, she advocates abandoning them and returning to Sewall Wright’s 3model. Although this model has provendimensional fitness landscape enormously useful, so has the EEA. We suspect it will retain its place at the core of evolutionary approaches to human behavior. Zuk’s maincritique of the mismatch perspective is empirical, specifically that species can and do evolve quite rapidly, meaning that they do not stay mismatched for long. Chapter 3 is devoted to describing rapid evolution in a wide variety of nonhuman species. Other chapters focus on humans’ rapidlyevolved adaptations for processing lactose, living at high altitude, and responding to various pathogens. These chapters provide a powerful lesson for mismatch proponents that the absence or occurrence of evolutionary change must be considered case by case, not assumed. But Zuk ought to heed this empirical lesson too. Highlighting examples of rapid evolution while neglecting cases of persistent mismatch is misleading. The hypothetical offered above of islandliving prey whose adaptations remain mismatched to novel predators has numerous empirical manifestations. For example, none of the flightless bird species of New Zealand have evolved flight in the 700 years since humans and other mammalian predators arrived, and the behavioral responses used by many species, such as freezing, are remarkably ineffective (Innes, Kelly, Overton, and Gillies, 2010). Many human traits also remain mismatched, although they could have conceivably undergone selection. For instance, in Akita, Japan, people have traditionally enjoyed high salt diets, but their high rates of hypertension and stroke show that they remain physiologically unadapted to it (MacGregor and Wardener, 1998). Of course, many significant human mismatches are not mismatches to the paleolithic but to the very recent past. One example is our tendency to draw environmental inferences from observations of fictitious, exaggerated, or infrequent events on television and in other media. Media distortion can lead us to be unsatisfied with the attractiveness of
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Throwing out the mismatch baby with the paleobathwater
our romantic partners (Kenrick, Gutierres, and Goldberg, 1989) and to irrationally respond to rare events, such as shark attacks and terrorist plots (Gaissmaier and Gigerenzer, 2012). A more striking mismatch case was the extreme susceptibility of indigenous Americans to Europeandiseases,” such as measles and small“crowd pox. To be fair, Zuk concedes that such mismatches could occur and acknowledges some candidates, such as preferences for candy bars rather than fibrous foods and lying back in an easy chair rather than taking vigorous hikes. But these cases receive only cursory attention inPaleofantasy, generally dismissed as if too obvious to warrant serious consideration. An Unknowable Past A second major argument in Zuk’s book is that, even if mismatches occur, we aren’t in a position to understand them. This is because knowledge of our past, particularly our lifestyles in the paleolithic, is incomplete. Logically, of course, Zuk is correct: We cannot directly measure paleolithic behavior and it does not fossilize. Nonetheless, converging lines of evidence allow us to confidently say that paleolifestyles would have nearly always included the following: clothing; spoken but not written language; diets with both animal and vegetable matter; cooking; tool making; longterm heterosexual relationships; these relationships occurring in the context of larger groups; favoring close kin; positive relations with nonkin; threat of intergroup conflict; sexual division of labor; art; rites of passage; infants in nearly constant skintoskin contact with an adult, usually the mother; weaning after two years of age; and substantial investment in childcare by non mothers. Some of these may seem too obvious to bother mentioning. However, almost every one diverges from the lifestyle of some contemporary human societies or at least one great ape species. Thus, they may have important, if underexplored, implications. Zuk acknowledges several of these points about the past but does not discuss them in depth except in a few cases, such as physical activity and diet. One would think that given the book’s thesis, though, it would have included a systematic appraisal of what we do and do not know about paleolifestyles and the evidentiary basis of this knowledge. That would seem better than offering the broad generalization that our knowledge is severely limited. Ironically, in critiquing various popular paleolifestyle recommendations, generally by nonacademic writers, Zuk undermines her claim about our ignorance of the paleolithic. For example, she is correct that there is ample evidence to say that, contrary to some paleo fitness popularizers, humans do possess adaptations for frequent aerobic exercise, especially distance running. That a specific mismatch hypothesis can be ruled out is a strength of the mismatch perspective, not a weakness. A related reason why we cannot specify much about the past, according to Zuk, is that human lifestyles are and were too variable to permit valid generalizations. Here Zuk falls into the trap of anthropologists who are so prone to celebrate the exotic that they become blind to the universal (Brown, 1991). For example, Zuk spends many pages considering whether humans are truly monogamous or polygynous and concludes that we are simply variable. This is undeniable, but it overlooks that both are kinds of marriage, and the mechanisms underlying romantic attachment seem to be universal (Jankowiak and
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Fischer, 1992). Across species, long term heterosexual relationships are highly unusual, so marriage in humans warrants careful scrutiny, not dismissal due to its variability. Moreover, contrary to what Zuk implies, serious scholars have not been endlessly debating whether humans are truly monogamous or polyg ynous; instead they have been testing and refining hypotheses to explain the variability (Henrich, Boyd, and Richerson, 2012). We also note that some of Zuk’s claims of variability seem weak. For instance, she repeatedly asserts that the sexual division of labor, although occurring in most societies, is not universal. This disagrees with scholarship focused on the issue (Marlowe, 2007; Murdock and Provost, 1973), and Zuk’s claim is based on scant evidence; the supporting endnote merely says, “Author conversation with Jane Lancaster, circa 1987”(p. 286). In fact, one claim of universality that Zuk does seem eager to embrace is that human sex differences are smaller than is generally believed. However, her consideration of the data is quite selective. When discussing humans’ supposedly modest sexual dimorphism, for example, Zuk notes that men typically are only 510% taller than women; she neglects to mention that, on average, men possess 5090% more strength and upperbody muscle mass (Puts, 2010). Useless Paleofantasies The third, and most important, argument inPaleofantasy is that the mismatch perspective has not proven beneficial. Zuk makes this point chiefly by exposing pitfalls in popular invocations of mismatch, especially paleodiets and paleofitness programs. For instance, some paleodiets eschew all dairy products while others advocate a nearly completely carnivorous diet. Zuk’s handling of this material is entertaining and insightful. Nonetheless, in her zeal to reveal the weakness of a mismatch perspective, Zuk repeatedly hits the easy targets but ignores more judicious recommendations, especially by academic scholars. In the 1980s, for example, Eaton, Konner, and Shostak developed a paleodiet, which was controversial at the time but presaged many increasingly accepted recommendations, such as dramatically reducing salt intake and replacing refined cereal grains with fibrous fruits and vegetables (Konner and Eaton, 2010). Zuk similarly downplays the value of a mismatch perspective in other areas. In her chapter on families, Zuk reviews crosscultural variability in infant care, especially breastfeeding, cosleeping, and attentiveness to crying. Western, especially American, parents often deviate markedly from typical patterns, ones that almost certainly would have prevailed in the paleolithic. Most notably, Western infants rarely experience extended breast feeding and frequently are left to sleep alone. Zuk acknowledges infant care is a case where a mismatch perspective could prove essential, even prescriptive. However, sheeventually dismisses this because, “We have obviously already altered childrearing practices in many different ways around the world, and most children grow up just fine” (p. 218). Granting a free pass to typical Western infant care practices gives short shrift to the mismatch perspective, and, more importantly, may cause harm. Cosleeping is strongly associated with successful breastfeeding (Gettler and McKenna, 2011), and extended breastfeeding, in turn, reliably correlates withnumerous positive outcomes for infants’ Evolutionary Psychology–ISSN 14747049–Volume 11(1). 2013. 266
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health, growth, and development (Horta, Bahl, Martines, and Victora, 2007). These facts may help explain why the mental health of contemporary U.S. children is poorer than in previous decades and worse than in most developed nations (Narvaez, Panksepp, Schore, and Gleason, 2012). We certainly hope Zuk’s “anything goes” is not used to statement bolster campaigns and legislation prohibiting cosleeping in the U.S. (McKenna and McDade, 2005). Another productive mismatch area that Zuk neglects is the field of evolutionary psychology. Zuk reveals a bias towards the field by defining it as, “a field thatpurports[our emphasis]behavior using evolutionary principles...” (p. 57). Thisto explain human attitude may stem from ignorance:Paleofantasy repeatedly cites Cosmides and Tooby’s(1997) online primer, a superb, if somewhat dated, source, but, besides this, there is virtually no mention of evolutionary psychology scholarship from academics. This neglect can be readily seen in the discussion of human mating, where Zuk repeatedly cites various blogs and Ryan and Jethá’s (2010) sensationalistic but thoroughly discredited book(Saxon, 2012), yet ignores hundreds of peerreviewed empirical studies on the topic. In fact, there is not a single reference to David Buss’ work, andPaleofantasy’s twenty page bibliography only includes a single paper from the leading evolutionary psychology journal,lovEoitun and Human Behavior. As we trust most readers of this journal recognize, evolutionary psychology’s impact extends far beyond mating and sexuality. The field has contributed to the understanding of many domains, including perception, memory, altruism, intergroup prejudice, and cultural transmission (Buss, 2005). Evolutionary psychologists have made many applied contributions as well. This is perhaps best recognized in evolutionary psychiatry, but applications now extend to the arts, marketing, education, and public health (Roberts, 2012). The bedrock of almost all this scholarship is a mismatch perspective, and it is regrettable that Zuk did not highlight some of these successes. Conclusion We have critiqued the strong version of Zuk’s thesis, that a mismatch perspective is unproductive. An important question is whetherPaleofantasyactually holds to that strong version. Arguably the answer is no, because Zuk is often moderate, acknowledging that mismatches can and sometimes do occur and that there is much that we can learn by characterizing our past. Nonetheless, we believe that, on balance, the book does hold to the strong version, and this is revealed by its nearly complete failure to acknowledge cases where a mismatch perspective has been illuminating. In sum, Zuk has written a wideranging, accessible, and stimulating book, but one that mainly triumphs in dispatching paleohucksters, anonymous bloggers, and scholarly straw men. In failing to acknowledge the successes of the mismatch perspective, Zuk has reached the wrong conclusion: The mismatch perspective has not been a failure; it has been tremendously fruitful. Yes, we must strive to do a better job employing this perspective, but, given the state of today’s world, we cannot afford to back down from the challenge.
References
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