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Time to Evolve

Katie L. Burke

PALEOFANTASY: What Evolution Really Tells Us About Sex, Diet, and How We Live. Marlene Zuk. 337 pp. W. W. Norton and Company, 2013. $27.95.

If you have the sense that interest in our early ancestors’ habits has grown of late, Google can back up your supposition: Searches including the term “paleo” have increased exponentially over the past 10 years, and most of those searches were made by people in the United States. “Paleo diet” and “paleo recipes” are among the most common phrases that include the term. Marlene Zuk, a professor of behavioral ecology and evolutionary biology at the University of Minnesota and the author of several previous books, greets this interest with healthy skepticism. Zuk aptly repurposes the term “paleofantasies,” coined by anthropologist Leslie Aiello, to describe the belief that “modern lives are out of touch with the way human beings evolved and that we need to redress the imbalance.” Such paleofantasies are rampant in Western pop culture, and in discussing them, Zuk cites a wide array of sources, from the New York Times’s health blog to the Chronicle of Higher Education, and from Christopher Ryan and Cacilda Jethá’s Sex at Dawn (2011) to Frans De Waal’s Our Inner Ape (2006). She then goes about debunking erroneous ideas, using examples and models from evolutionary biology.

In a chapter on diet, Zuk writes of a 2009 conference on evolution and medicine at which she encountered exercise physiologist Loren Cordain. The Paleo Diet, Cordain’s 2002 book, has sold more than 100,000 copies; he was giving a talk on how certain foods affect the digestive health of people with a variation in an immune system gene. Zuk stood up to ask, “Why . . . has this inability to properly digest all these common foods persisted? Surely it should have been selected out of the population.” Cordain answered that there had not been enough time for humans to evolve since the rise of agricultural societies 10,000 years ago—not an answer likely to satisfy someone such as Zuk who studies rapid evolution. (What constitutes “rapid” varies for different species, but the field considers change over amounts of time much smaller than were previously considered.) “Plenty of time,” she countered. Paleofantasies is, in a sense, the long answer to why 10,000 years is more than enough time for humans to evolve to our modern context.

Zuk offers many examples of rapid evolution in humans revealed by the discovery of new genes. Some people digest starches based on the number of duplicate genes for making the enzyme amylase. Some are prone to be better runners because they have particular versions of the gene that makes a protein controlling fast-twitch muscle fibers. She notes, “If the genetic tools to characterize each individual’s diet-related genes are developed, we might be able to examine the suitability of particular diets for certain people. But that day has not yet come.” She also tackles assumptions about our adaptations (or lack thereof) to long-distance running, modern disease and monogamous relationships.

Although humans may not be perfectly evolved to every modern situation, Zuk contends, neither were early humans perfectly evolved to their Paleolithic environment. “To think of ourselves as misfits in our own time and of our own making,” she writes,

flatly contradicts what we now understand about the way evolution works—namely, that rate matters. That evolution can be fast, slow or in-between, and that understanding what makes the difference is far more enlightening, and exciting, than holding our flabby modern selves up against a vision—accurate or not—of our well-muscled and harmoniously adapted ancestors.

Zuk makes clear that popularized answers about our ancestral diet, health, sex lives and exercise reflect our societal biases and demonstrate widespread misunderstandings about evolution. The evolutionary landscape is wonderfully complex; to oversimplify it is to miss the beauty of life’s diversity.

Katie Burke is an associate editor at American Scientist. She received her Ph.D. in biology from the University of Virginia in 2011. She blogs about ecology at

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