Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live (33 page)

If your earwax knowledge is a bit scanty, you may not know that earwax comes in two distinct forms: wet and dry. The dry form is most common among East Asians, while the wet form, described by the researchers as “brownish and sticky,” predominates in Africa and Europe. In southern and central Asia, the two forms occur in more or less equal proportions. The wet form is therefore likely to be the ancestral form, since humans evolved in Africa, with the dry form arising later, probably in northern Asia, given that the northern Chinese and Korean samples exhibited it. Moving south through Asia, the dry form becomes less common, perhaps because people with that form intermarried with southern Asians carrying the wet-earwax gene. Native Americans also exhibit the dry form, consistent with the idea that their ancestors were originally from Asia and came across the Bering Strait via Siberia.

The form of one’s earwax does not seem to matter much in the greater scheme of things, so far as we can tell. It does keep dirt and insects out of the ear canal, but no evidence suggests that one form or another is more efficient at this task. The genetic change may have come about through genetic drift, or because it is linked to another, more significant characteristic. The scientists who conducted the study speculate that because earwax type is associated with the amount of sweating, and hence body odor, these traits and not the earwax itself might have been the targets of selection. Asians tend to sweat less than Europeans, and the authors suggest that this attribute might have been advantageous in the cold climate where the ancestors of northeast Eurasians lived. This part of the story is, of course, difficult to substantiate, but the detail with which the change in DNA was documented underscores scientists’ increasing ability to trace evolution in our recent past. And the earwax story offers hope that scientists will be able to meticulously track a single change to its adaptive advantage in more cases, enabling us to determine exactly how important big selective sweeps have been in our history.

The rapid river of change

The humble earwax gene and the other examples I have provided in this book are only a tiny fraction of the evidence for recent human genetic change. And “recent” can mean 3,000 years, 10,000, or 200,000, depending on one’s perspective. For that matter, even trying to rank one or another trait as “most recently evolved” says more about the human tendency to keep score than it does about evolution itself. As I mentioned earlier in the chapter, no prizes are awarded for “most recently evolved,” and if they were, microbes would be the clear winners. But it seems to be a human tendency, evolved or not, to want to be good at things; in a 2009
Scientific American
article musing on the fate of
Homo sapiens
, University of Washington paleontologist Peter Ward reassures us that “humans are first-class evolvers.”
³²

Breathless headlines aside, what is wrong with trying to excel at evolution, or with being a tad competitive about which characteristic evolved most recently? The problem is that this kind of goal-directed thinking still presents evolution as a process with an end point; being good at something implies a skill that can be mastered and, once mastered, allows us to move on to something else. But of course our ancestors were also evolving, and as I discussed in Chapter 1, no organism gets to a point of perfect adaptation, heaves a sigh of genetic relief, and stops. All of our characteristics, and all of our genes, are subject to change at different rates, making the declaration of a finished product impossible.

This does not mean that evolution acts in the same way on all creatures, or on all aspects of them—or that all adaptations are possible. Scientists do not talk about being “good at” evolution, but they do consider what is rather awkwardly termed evolvability. “Evolvability” refers to the capacity of an organism to generate the raw material of evolution—namely, heritable variation—so that natural selection can act. More variation means more opportunities to survive a flood, or find more mates, or change bill size. Some people confine discussion of evolvability to occurrences within populations, like a change in coat color from white to brown in mice living in light or dark soil, while others use it to explain how evolutionary novelties, such as wings, arise in entire groups of organisms. Evolvability is not a virtue, but a property of organisms and their genes, and it may fluctuate over time.

The Greek philosopher Heraclitus was supposed to have said, “No man ever steps in the same river twice.” He was known as “Heraclitus the Obscure,” in part because many of his works were difficult to interpret. Indeed, some people suggest that this saying means that nothing retains its identity, while others claim Heraclitus meant that because life is constantly changing, one can always reinvent oneself. As applied to evolution, one could interpret his remark to mean that organisms are responding to a continually changing environment, the river, and hence evolution itself is continual too. To truly emulate evolution, however, the river would need to be unending, and the foot that stepped into it would need to be different with every attempt at wading. Not only are our lives different from those of our Pleistocene ancestors, but their lives were different from those of their ancestors as well, and on it goes.

Relinquishing the paleofantasy

From our diets to our dating habits, paleofantasies are everywhere, not only on websites yearning for a more natural lifestyle but in places like the
Chronicle of Higher Education
, which recently ran an article on why people like crispy food that invoked our evolutionary predilection for the crunchy delights of insect snacks (apparently the sound made when eating such foods also led to their having “a privileged place in the brain”).
³³
And the paleofantasies go beyond simply making up “just-so stories,” as the late evolutionary biologist Stephen Jay Gould called them, about the evolutionary significance of everything. We are not only constructing scenarios of why our foibles might have been adaptive; we are fossilizing evolution itself.

A simpler life with more exercise, fewer processed foods, and closer contact with our children may well be good for us. But we shouldn’t seek to live that way because we think it emulates our ancestors. We can mimic the life of a preindustrial, or preagricultural, society only in its broadest sense. Rather than trying to use our past to proscribe our present, or our future, we can use it as a way to understand where we came from. Paleofantasies call to mind a time when everything about us—body, mind, and behavior—was in sync with the environment. But as the previous pages have shown, no such time existed. We, and every other living thing, have always lurched along in evolutionary time, with the inevitable trade-offs that are a hallmark of life. We have nothing to lose by giving up our paleofantasies, and everything to gain.

For one thing, we gain some relief from that nagging sense that we are mismatched to our environment, doomed to flounder in a modern world to which we are not suited. True, the specifics of twentieth- or twenty-first-century life are novel: computers, high-rise buildings, cell phones. But instead of denouncing modern living as unsuitable to our Stone Age genes, we need to figure out just what parts of that life send us too far out of our evolutionary zone of tolerance, and to do that we need data, not blanket condemnation. Usually, we can make broad generalizations and do not need to sweat the details. For example, sedentary living is clearly linked to poor health, but we do not have to emulate a mammoth-spearing caveman to remedy the problem. We just need to get up off the couch.

For another thing, we can stop looking for models of our ancient selves in contemporary foraging peoples or the great apes. Everything alive today is just as evolved as every other organism, and nothing mirrors human history in its entirety. We are all related, of course, and we can see how humans, or other primates, respond to different selection pressures in different environments, but no species has a premium on being best adapted to its surroundings.

Relinquishing our paleofantasy also helps us feel more connected to other organisms; just because our lives seem different from those of our paleo ancestors, or our great-ape relatives, does not mean we and they have not been subject to the same forces of evolution. We can even be happier without feeling that we are bucking the system; an article in
Self
magazine on becoming more optimistic quoted neuropsychologist Rick Hanson: “Because the human brain evolved during a time when danger was everywhere, it has a built-in negativity bias. For humans to survive under these dire straits, the brain regions responsible for detecting threats had to be turbocharged. Evolution favored those who were able to react to danger with lightning speed.”
³⁴
But this Chicken Little attitude is not uniquely human (and I can attest from personal experience that real chickens do, indeed, behave as though danger lurks in every corner, including corners with nothing more threatening than a food bowl). All animals evolved when danger was everywhere, because, well, danger
is
everywhere. But humans didn’t evolve to be any more negative than the next species, and being alert to threats does not make us naturally, or unusually, glum.

Giving up the paleofantasies lets us appreciate that all environments, old and new, leave their mark. As with the baby’s foot altered by shoes in modern times and by barefoot walking in ancient times, or the different microbes that flourish in our guts depending on our diets, whatever we choose has consequences, and choices have to be made. We do not have genes plunked wholesale into one environment or another, whether Paleolithic, medieval, or industrial; we have genes that respond to that environment and to each other. A comment on
Mark’s Daily Apple
, the blog that features Grok, cautioned, “The major difference we face now compared to our ancient ancestors is that except in rare instances change comes at us more quickly today.”
³⁵
Perhaps. But change is continuous, and those ancient ancestors encountered changes as well; they domesticated animals, they grew crops, and they dealt with diseases. Change does not have to mean disaster. Sometimes it just creates more change.

Acknowledgments

I am always grateful to my colleagues and the scientists all over the world who share their data and stories, give me advice, and try to keep me (sometimes successfully and sometimes not) out of trouble. This gratitude is particularly pronounced for this book, as I have ventured into territory usually reserved for anthropologists, and that is ground often marked by acrimony and rancor. The anthropologists whom I have been lucky enough to consult have nonetheless been unfailingly helpful and kind. I am especially grateful to Gene Anderson, Rob Boyd, Becky Cann, Greg Downey, Kristen Hawkes, John Hawks, Rosemary Joyce, Sang-Hee Lee, Joan Silk, and Tim White. Leslie Aiello deserves a special mention for her willingness to let me use the word “paleofantasy,” though I have stretched it far past her original intent. Becky Cann heroically saved me at the last minute with a terrific figure of a selective sweep. A number of biologists, including many of my colleagues from the Department of Biology at UC Riverside, have influenced my thinking about rates of evolution. I, along with many of the ideas in this book, found a gracious reception at Uppsala University in Sweden and the School of Animal Biology at the University of Western Australia.

I thank my writer friends, who inspire me in ways large and small: Deborah Blum, Susan Maushart, Virginia Morell, Susan Straight, and Carl Zimmer. Angela von der Lippe, Laura Romain, and Anna Mageras are wonderful editors who care about books, an increasingly rare breed. My agent Wendy Strothman and Lauren MacLeod from the Strothman Agency are always helpful and encouraging, and I appreciate Lauren’s adeptness with social media, even if I am still somewhat paleo in my own use of it. Stephanie Hiebert did a heroic job of copyediting. Finally, John Rotenberry has been a stalwart and much appreciated supporter.

Notes

Introduction

1 Author visit to Anders Götherström’s laboratory at Uppsala University, Sweden, December 2009.

2 Holland, “Cavewoman’s Guide to Good Health.”

3 Ehkzu, March 6, 2010 (8:39 p.m.), comment on R. C. Rabin, “Doctors and Patients, Not Talking about Weight,”
Well
(blog),
New York Times
, March 16, 2010, http://well.blogs.nytimes.com/2010/03/16/doctors-and-patients-not-talking-about-weight/?apage=4#comment-495227.

4 ACW, August 20, 2008 (12:11 p.m.), comment on T. Parker-Pope, “Why Women Stop Breast-Feeding,”
Well
(blog),
New York Times
, August 15, 2008, http://well.blogs.nytimes.com/2008/08/15/why-women-stop -breast-feeding/?apage=8#comment-51267.

5 tman, July 16, 2010 (11:26 a.m.), comment on G. Reynolds, “Phys Ed: The Men Who Stare at Screens,”
Well
(blog),
New York Times
, July 14, 2010, http://well.blogs.nytimes.com/2010/07/14/phys-ed-the-men-who-stare-at-screens/?apage=8#comment-548092.

6 Balter, “How Human Intelligence Evolved.”

7 Shubin,
Your Inner Fish
.

8 Wade,
Before the Dawn
, 70.

9 Zuk, Rotenberry, and Tinghitella, “Silent Night”; Tinghitella and Zuk, “Asymmetric Mating Preferences.”

10 Simpson,
Tempo and Mode in Evolution
, xv.

11 Coyne,
Why Evolution Is True
.

12 McKie, “Is Human Evolution Finally Over?”

13 Cochran and Harpending,
10,000 Year Explosion
.

Chapter 1: Cavemen in Condos

1 Goldstein, “New Age Cavemen and the City.”

2 “Diet Fad from the Stone Age.”

3 Hawks, “Cavemen Are Happy.”

4 Goldstein, “New Age Cavemen and the City.”

5 KP, August 22, 2007 (8:53 a.m.), comment on topic “So Close and Yet So Far. . .,”
Caveman Forum
, http://cavemanforum.com/research/so-close-and-yet-so-far/msg2590/#msg2590.

6 Simopoulos and Robinson,
Omega Diet
, 24.

7 Jacobsen, “Essential Caveman Lifestyle.”

8 Adam, November 4, 2010 (11:51 a.m.), comment on C. McDougall, “Born to Run the Marathon?”
Well
(blog),
New York Times
, November 4, 2010, http://well.blogs.nytimes.com/2010/11/04/born-to-run-the-marathon/?apage=4#comment-594535.

9 Author conversation with Greg Downey, September 2010.

10 One example can be found at http://www.paleojay.com/2011/12/getting-rid-of-eyeglasses.html.

11 Wrangham,
Catching Fire
.

12 Gibbons, “Lucy’s Toolkit?”

13 Ibid.

14 Boyd and Silk,
How Humans Evolved
(5th ed., 2009), 279.

15 Milius, “Tapeworms Tell Tales.”

16 Green et al., “Draft Sequence of the Neandertal Genome.”

17 Boyd and Silk,
How Humans Evolved
(6th ed., 2012), 292.

18 Enard et al., “Molecular Evolution of FOXP2.”

19 Edward Hagen, “What Is the EEA and Why Is It Important?”
Evolutionary Psychology FAQ
, last modified September 8, 2004, http://www.anth.ucsb.edu/projects/human/evpsychfaq.html.

20 Rosemary Joyce, e-mail message to author, November 11, 2010.

21 Bower, “Strange Case of the Tasaday.”

22 Rosemary Joyce, e-mail message to author, November 11, 2010.

23
John Hawks Weblog: Paleoanthropology, Genetics and Evolution
, http://johnhawks.net.

24 Ibid., under “humor,” http://johnhawks.net/weblog/topics/humor.

25 Hawks, “Neandertal Stories on Parade.”

26 Glendinning, “Neanderthals: Not Stupid.”

27 Keim, “Neanderthals Not Dumb.”

28 “Stone Me.”

29 Martin, “We’ve All Suspected,” cited in Hawks, “Ozzy Osbourne.”

30 Smith et al., “Dental Evidence”; “Evolution: Neanderthals Matured Fast.”

31 Sponheimer and Lee-Thorp, “Isotopic Evidence.”

32 Alleyne, “Neanderthals Really Were Sex-Obsessed Thugs.”

33 “Neanderthals Had a Naughty Sex Life.”

34 Nelson et al., “Digit Ratios Predict Polygyny in Early Apes.”

35 A good summary can be found in Manning,
Digit Ratio
.

36 “Cavemen Randier Than People Today.”

37 Joyce, “Fingering Neanderthal Sexuality.”

38 Nelson et al., “Digit Ratios Predict Polygyny in Early Apes.”

39 Kratochvíl and Flegr, “Differences in the 2nd to 4th.”

40 Hawks, “ ‘Naughty Neandertals’ Did What?”

41 Wrangham and Pilbeam, “African Apes as Time Machines.”

42 Wrangham and Peterson,
Demonic Males
.

43 Zihlman, “Paleolithic Glass Ceiling.”

44 White et al., “
Ardipithecus ramidus
.”

45 Wrangham and Pilbeam, “African Apes as Time Machines.”

46 Brown,
Human Universals
, 5.

47 Ibid., 6.

48 Joyce, “Do Our Ancestors Walk among Us?”

Chapter 2: Are We Stuck?

1 Radosavljevic, “Stone Age Sights.”

2 Cosmides and Tooby, “Evolutionary Psychology.”

3 Cordain,
Paleo Diet
.

4 Diamond, “Worst Mistake.”

5 Cochran and Harpending,
10,000 Year Explosion
.

6 Diamond, “Worst Mistake.”

7 O’Connell, “Is Farming the Root of All Evil?”

8 Wells,
Pandora’s Seed
, 90.

9 Feeney, “Agriculture.”

10 General information about the beginning of agriculture comes from “Agriculture and Food,”
Food Encyclopedia
,
Huffington Post
, accessed October 2010, http://www.huffingtonpost.com/encyclopedia/definition/agriculture%20and%20food/23.

11 Denham, Iriarte, and Vrydaghs,
Rethinking Agriculture
, 6.

12 Cordain,
Paleo Diet
, 3.

13 Harris, “Agriculture, Cultivation, and Domestication,” 30.

14 Wells,
Pandora’s Seed
, 24.

15 Lee,
!Kung San
.

16 Diamond, “Worst Mistake.”

17 Kaplan et al., “Theory of Human Life History Evolution.”

18 Ibid.

19 Diamond, “Worst Mistake.”

20 Gage, “Are Modern Environments Really Bad for Us?”

21 Bowles, “Did Warfare?”

22 Singer, “Is Violence History?”

23 Cochran and Harpending,
10,000 Year Explosion
, 65.

24 Hawks, “Why Human Evolution Accelerated.”

25 Cochran and Harpending,
10,000 Year Explosion
.

26 Powell, Shennan, and Thomas, “Late Pleistocene Demography.”

27 Wells,
Pandora’s Seed
, 53.

28 Cosmides and Tooby, “Evolutionary Psychology.”

29 Ibid.

30 Edward Hagen, “What Is the EEA and Why Is It Important?”
Evolutionary Psychology FAQ
, last modified September 8, 2004, http://www.anth.ucsb.edu/projects/human/evpsychfaq.html.

31 Strassmann and Dunbar, “Human Evolution and Disease.”

32 Britten, “Divergence between Samples.”

33 Marks,
What It Means to Be 98% Chimpanzee
, 29.

34 Cordain,
Paleo Diet
, 9.

35 Rebecca Cann, e-mail message to author, December 2010.

36 Carroll, “Genetics and the Making of
Homo sapiens
.”

37 Ibid.

38 Tooby and Cosmides, “Past Explains the Present.”

39 Irons, “Adaptively Relevant Environments.”

40 Ibid.

41 Ibid.

42 Wright, “Roles of Mutation.”

Chapter 3: Crickets, Sparrows, and Darwins—or, Evolution before Our Eyes

1 Hendry and Kinnison, “Perspective.”

2 Bumpus, “Elimination of the Unfit.”

3 Haldane, “Suggestions as to Quantitative Measurement.”

4 Gingerich, “Rates of Evolution”; Gingerich, “Quantification and Comparison.”

5 Robinson Jeffers, “The Beaks of Eagles,” PoemHunter.com, submitted April 12, 2010, http://www.poemhunter.com/poem/the-beaks-of-eagles.

6 Grant and Grant, “Unpredictable Evolution”; Seger, “El Niño and Darwin’s Finches.”

7 Ogden Nash, “The Guppy,” PoemHunter.com, submitted January 13, 2003, http://www.poemhunter.com/poem/the-guppy.

8 Reznick et al., “Evaluation of the Rate of Evolution.”

9 Reznick, Ghalambor, and Crooks, “Experimental Studies of Evolution in Guppies.”

10 Reznick, Ghalambor, and Crooks, “Experimental Studies of Evolution in Guppies”; Reznick et al., “Evaluation of the Rate of Evolution.”

11 Ibid.

12 Berthold et al., “Rapid Microevolution.”

13 Barrett et al., “Rapid Evolution of Cold Tolerance.”

14 Carroll et al., “And the Beak Shall Inherit”; Carroll, “Facing Change.”

15 Schoener, “Newest Synthesis.”

16 Hendry and Kinnison, “Perspective.”

17 The Ten Thousand Toads Project.
Turtle Care Sunshine Coast
, accessed July 16, 2012, http://www.turtlecare.com.au/10k-toads-project.php.

18 “Kill Cane Toads Humanely: RSPCA,”
Animals Australia
, February 19, 2011, http://www.animalsaustralia.org/media/in_the_news.php?article=1948.

19 The Kimberley Toadbusters, http://www.canetoads.com.au.

20 Phillips and Shine, “Adapting to an Invasive Species.” See also http://www.canetoadsinoz.com.

21 Phillips, Brown, and Shine, “Evolutionarily Accelerated Invasions.”

22 “Cane Toad Evolution,” CaneToadsinOz.com, accessed July 16, 2012, http://www.canetoadsinoz.com/cane_toad_evolution.html.

23 Ibid.

24 Coltman et al., “Undesirable Evolutionary Consequences”; Allendorf and Hard, “Human-Induced Evolution.”

25 Eldridge, Hard, and Naish, “Simulating Fishery-Induced Evolution.”

26 Wolak et al., “Contemporary, Sex-Limited Change.”

27 Rudolf, “Speedy Evolution, Indeed.”

28 Wirgin et al., “Mechanistic Basis of Resistance to PCBs.”

29 Ibid.

30 Elmer et al., “Rapid Sympatric Ecological Differentiation.”

31 Halfwerk et al., “Negative Impact of Traffic Noise.”

Chapter 4: The Perfect Paleofantasy Diet: Milk

1 Robert M. Kradjian, “The Milk Letter: A Message to My Patients,” Notmilk.com, accessed February 2011, http://www.notmilk.com/kradjian.html.

2 Robert Cohen, “Detox from Milk: Seven Days,” Notmilk.com, accessed February 2011, http://www.notmilk.com/detox.txt.

3 interfool, January 1, 2011 (6:59 p.m.), comment on T. Bilanow, “Salads with Crunch, Sweetness and Zest,”
Well
(blog),
New York Times
, December 31, 2010, http://well.blogs.nytimes.com/2010/12/31/salads-with-crunch-sweetness-and-zest/#comment-616849.

4 Warren Dew, February 1, 2011 (7:36 p.m.), reply #3 on topic “Whats [
sic
] Wrong with Cheese?”
Caveman Forum
, http://cavemanforum.com/diet-and-nutrition/whats-wrong-with-cheese/msg47077/#msg47077.

5 Schiebinger, “Why Mammals Are Called Mammals.”

6 Information about milk types comes from the University of Guelph’s Department of Food Science, http://www.uoguelph.ca/foodscience/content/table-3-composition-milk-different-mammalian-species-100-g-fresh-milk.

7 Bloom and Sherman, “Dairying Barriers.”

8 Beja-Pereira et al., “Gene-Culture Coevolution.”

9 Boyd and Silk,
How Humans Evolved
.

10 Gerbault et al., “Evolution of Lactase Persistence.”

11 Alan R. Rogers, notes for lecture titled “Evolution of Lactase Persistence,” November 16, 2009, http://content.csbs.utah.edu/~rogers/ant5221/lecture/ lactase-2x3.pdf.

12 Gerbault et al., “Impact of Selection and Demography.”

13 Anderson and Vullo, “Did Malaria Select?”

14 Tishkoff et al., “Convergent Adaptation.”

15 Ingram et al., “Lactose Digestion.”

Chapter 5: The Perfect Paleofantasy Diet: Meat, Grains, and Cooking

1 Revedin et al., “Thirty Thousand-Year-Old Evidence.”

2 Henry, Brooks, and Piperno, “Microfossils in Calculus.”

3 Henry et al., “Diet of
Australopithecus sediba
.”

4 Hirst, “Grinding Flour.”

5 Karen, December 11, 2010 (12:29 p.m.), comment on T. Parker-Pope, “Pass the Pasta!”
Well
(blog),
New York Times
, December 10, 2010, http://well.blogs.nytimes.com/2010/12/10/pass-the-pasta/#comment-608687.

6 KevinJFUm, August 3, 2011 (9:26 p.m.), comment on topic “Are Meat Cravings Normal?”
Caveman Forum
, http://cavemanforum.com/diet-and-nutrition/are-meat-cravings-normal.

7 Cordain,
Paleo Diet
.

8 Vonderplanitz,
We Want to Live
.

9 Wolf,
Paleo Solution
.

10 Voegtlin,
Stone Age Diet
, 3.

11 Ibid., 1.

12 Ibid., 23–24.

13 Mallory, August 2, 2011 (5:09 p.m.), comment on topic “Do Carbs Make Your Nose Rounder?”
PaleoHacks
, http://paleohacks.com/questions/ 55442/do-carbs-make-your-nose-rounder#axzz20uvViyXl.

14 Evolution and Diseases of Modern Environments, at the Berlin Charité, October 2009.

15 Cordain,
Paleo Diet
, 3.

16 Ibid.

17 scott, October 19, 2010 (11:40 a.m.), comment on “The Stone Age Food Pyramid Included Flour Made from Wild Grains,
80beats
(blog),
Discover
, October 18, 2010, http://blogs.discovermagazine.com/80beats/2010/10/18/the-stone-age-food-pyramid-included-flour-made-from-wild-grains.

18 “Best Diets,”
U.S. News & World Report
, accessed July 17, 2012, http://health.usnews.com/best-diet.

19 Avery Comarow, “Best Diets Methodology: How We Rated 25 Eating Plans,”
U.S. News & World Report
, January 3, 2012, accessed July 17, 2012, http://health.usnews.com/best-diet/articles/2012/01/03/best-diets -methodology-how-we-rated-25-eating-plans.

20 “Paleo Diet,”
U.S. News & World Report
, accessed July 17, 2012, http://health.usnews.com/best-diet/paleo-diet.