Evolution

Salon spoke to Fodor over the phone from his home, about the problems with Darwin’s ideas, bloggers’ "obscene" comments on his work, and why Darwinism might be as unreliable as creationism.

In 2007, you wrote an article attacking Darwinism in the London Review of Books, and experienced a lot of backlash from both inside and outside of the scientific community. Why do you think people get so worked up about Darwinism?

It’s a theory that’s played all sort of roles in the foundations of biology. There’s a lot of people who think wrongly that if you didn’t have Darwinism the whole foundations of modern biology would collapse. I doubt that’s true. I’m sure it’s not. But if you tell people, "There’s this fundamental theoretical commitment you’ve made and there’s holes in it," they’ll want very much to defend that theory.

Most of the backlash to the book so far has been on blogs, which have been pretty obscene and debased. What’s upsetting is that they tell you that they think you’re an idiot, but they don’t tell you why -- people who aren’t part of the field or who may not, in many cases, know much about Darwin. I’m not sure that all people who have been blogging about it are very sophisticated. It’s frustrating because you don’t know who you’re talking to.

At some point you just have to stop worrying about the reaction and worry if the argument is any good. I don’t take the arguments that say, "This that can’t be true because of what I learned in Biology 101" very seriously.

 What is your beef with natural selection?

The main thing Darwin had in mind with natural selection was to come up with a theory that answers the question, "Why are certain traits there?" Why do people have hair on their heads? Why do both eyes have the same color? Why does dark hair go with dark eyes? You can make up a story that explains why it was good to have those properties in the original environment of selection. Do we have any reason to think that story is true? No.

According to Darwin, traits of creatures are selected for their contribution to fitness [likelihood to survive]. But how do you distinguish a trait that is selected for from one that comes along with it? There are a lot of interesting structures in creatures that have nothing to do with fitness.

Some variants in selection are clearly environmental. If you can’t store water you’ll do worse in a dry environment than if you can. But suppose that having a high ability to carry a lot of water is correlated for genetic reasons with skin color. How do you decide which trait is selected for by environmental factors and which one is just attached to it? There isn’t anything in the Darwinist picture that allows you to answer that question.

So we have no way of knowing whether a trait serves an evolutionary purpose?

Some traits are presumably selected for by the environment, and some of them are not. If somebody says Trait A affects fitness and Trait B does not, but Trait B comes with Trait A so you’ve got both traits in the organism, it’s very natural for somebody in the Darwinian tradition to think that Trait B has been selected for by the environment. But the answer is, it’s not there for anything.

Look, everybody has toenails, so you might ask yourself, why is it such a good thing we have toenails? It may be a case that in the environment there was some factor that favored toenails but there also may not.

As you explain in the book, it turns out many genes are far more tied together -- and gene expression is much more complicated -- than many people originally thought.

What the genetics has come to show is that traits are not independent, but complexly interconnected, and a lot of the effect that the environment has on an organism’s evolution depends on what organism it is.

There’s a famous fox-into-dog experiment, in which many generations of foxes were selected for being domestically trainable. As you would expect, when you select for domesticability, you get animals that behave less and less like their feral counterparts -- but you also get curly ears and kinked tails and changes in their reproductive system. Nobody had that in mind, but the structure of the organism groups all of these traits together. Why do these animals have kinky tails? They just happen to be structural correlates. Now the question is, how much of the evolutionary variance is determined by factors of the environment and how much is controlled by the organization of the organism, and the answer is nobody knows.

Most children learn about natural selection by learning the example of the giraffe’s long neck, which supposedly evolved because it allowed animals to graze higher branches. Does this mean that we’re giving schoolchildren the wrong information?

The inference runs that there’s this creature that has a long neck, so this creature was selected for having a long neck. That inference is clearly invalid. A creature that has a long neck may have that neck because a different trait was selected, and the long neck came along with it.

And in a sense, there are no such things as traits. The environment selects creatures. Animals can have long necks and toenails, but if you try to break such creatures apart into traits and you say, OK, "What selected this trait?" and, "What selected that trait?" you've made a mistake right from the beginning. The disintegration of the organism into traits is itself a spurious undertaking. Biologists have said for a long time that organisms aren’t like Swiss apples, you can’t tap them on a table and have them fall apart into distinct wedges. Selection is operating on whole organisms.

There's been increasing evidence in recent years that homosexuality has a genetic cause, which doesn’t exactly mesh with natural selection, given that gay people aren’t likely to have lots of children. Does your theory help explain the gay gene?

It’s not obvious what, when the environment was selecting for fecundity, would have selected for people who are gay. You could have gotten them innately as a result of something that has nothing to do with sexual performance.

Do you think people are defending Darwinism because they think any attack on Darwinism gives power to creationists, and they don't want creationists to get the upper hand?

I think there’s the sense that if you think that there’s something wrong with the theory you’re giving aid and comfort to intelligent design people. And people do feel very strongly about whether you want to do that.

When you do science, you try to find the truth. The problem with creationism, even if you’re not a hardcore atheist, as I am, is that anything is compatible with creationism. If God created the world, he could have created it any way he liked. So creationists, when faced with evidence of evolution, are happy to say that that’s the way God created the world. If it turns out that there is no process of evolution, they’d say OK, that’s fine too. Whatever turns out to be the case it’s compatible with God having created the world, so you can’t argue with their position or you throw your shoulders out.

As you explain in the book, one of the problems with Darwinism is that Darwin is inventing explanations for something that happened long ago, over a long period of time. Isn’t that similar to creationism?

Creationism isn't the only doctrine that’s heavily into post-hoc explanation. Darwinism is too. If a creature develops the capacity to spin a web, you could tell a story of why spinning a web was good in the context of evolution. That is why you should be as suspicious of Darwinism as of creationism. They have spurious consequence in common. And that should be enough to make you worry about either account.

If you're right, what do you think your argument means for the study of evolution?

If this is true, then we need to rethink the implications of Darwinism. Maybe the right question to ask is not what environmental variables are doing selection, but what kinds of complexes are they selecting on. One sees, even without God, how this Darwinian story could turn out to be radically wrong. You could see a massive failure of the evolutionary project, because wrong assumptions were made. 

The world is full of kooky religious extremists. Cameron gets plenty of street cred there for his Living Waters ministry Web site, where he and fellow science revisionist Ray Comfort test whether you are "good enough to go to heaven" (Hint: Don't bet on it) and let "hell's best secret" out of the bag.

But it takes a very special kind of kooky religious extremist to mess with one of the most influential works ever written. Who but the former Mike Seaver would use "common sense" to explain why evolution is just so much random crap? Fossil evidence be damned -- literally! Not since the Vatican got uppity about Galileo has the world seen such umbrage over scientific thought.

The sincerity of Cameron's mission is clear in the enthusiasm he brings to his ministry. And his ardent concern about evolution -- a subject God himself has never issued a statement on -- is genuine. The guy is really, really concerned that we are in the throes of a holocaust of souls here, bless his heart. And anybody who can show up at a college campus and tell students "Darwinism is atheism masquerading as science" may not be super high up on the intellectual food chain, but he's got crazy to spare.

Was this stunt shrewd or moronic? From the first it's been hard to tell. The plan, innocuously named "Origin Into Schools," was announced this September in a video featuring Kirk Cameron, a former television child star who co-founded a ministry called Living Waters with Comfort. There's something almost pitiable about the way Cameron crows over the scheme; he truly seems to find it ingenious. He points out that the University of California at Berkeley cannot prevent the action because "their own Web site" dictates that "anyone is free to distribute noncommercial materials in any outdoor area of the campus." "Besides," he gleefully adds, "what are they really going to do? Ban 'The Origin of Species'? That would be big news! Especially when their own bookstore sells it for $29.99!"

But if the university has a policy permitting the distribution of any "noncommercial materials," why not just hand out straightforward religious tracts, without the risk of spreading evolutionary theory yourself? Cameron makes several false and misleading claims at the beginning of the video about how "our kids" aren't allowed to "pray in public" or to "freely open a Bible in school." (In fact, the first time I ever read the Old Testament was, yes, for a class at U.C. Berkeley.) Printing a tract as a foreword to "The Origin of Species" is supposed to be a clever end run around this sort of "censorship," but then Cameron himself indicates that the censorship isn't actually happening since it's against university rules.

As for Comfort's introduction, it says very little about "The Origin of Species" per se, limiting itself to familiar creationist canards about the complexity of the human eye and the absence of "transitional forms" from the fossil record. (It's hard to lend much credence to the scientific arguments of a guy who thinks chimpanzees are monkeys.) There's a brief biographical section on Darwin's life, most of which has been plagiarized from a short text by Dr. Stan Guffey, as some bloggers have demonstrated. The rest has been plagiarized from Brian Regal's introduction to the Barnes and Noble edition of "The Autobiography of Charles Darwin," except for a timeline, which was plagiarized from an online resource. Nearly half of the introduction isn't even about evolution at all, and consists of a hodgepodge of strained sky-diving metaphors and horror stories about pedophiliac killers.

Lastly, although Comfort claimed in advance that "not one jot or tittle" of the text of "The Origin of Species" would be missing from his edition, four entire chapters were omitted. Comfort said that this was an error limited to the first printing, but his critics have claimed that these sections were intentionally left out because they contain strong evidence for Darwin's theory.

Perhaps, but that presupposes that Comfort actually expects students to read the books his minions distributed. Any college professor can tell you how difficult it is to get students to do the assigned reading, let alone plow through a 19th-century scientific treatise that isn't even on the syllabus. Look just a little harder and you can tell that Origin Into Schools has nothing to do with books, reading, the intellectual formation of what Cameron calls "our future doctors, lawyers and politicians" or the free exchange of ideas.

The Living Waters Web site reveals Comfort to be obsessed with goading atheists, specifically Richard Dawkins, who is featured in almost as many of the site's videos as Comfort is and whom Comfort has challenged to a public debate. (Dawkins has refused on the grounds that Comfort is an "ignorant fool," but some negotiation appears to be ongoing.) Dawkins nicknamed him "Banana Man," after Comfort used the handy snacking features of the fruit to argue for intelligent design. Comfort recently sent Dawkins an anonymous "gift basket" containing his edition of "The Origin of Species" plus a banana, and said, with regard to the proposed debate, "I think I can smell English chicken."

Apart from the Cameron video, the main mention of Origin Into Schools on the Living Waters home page consists of an article titled "Origin of Species Campaign Enrages Atheists." The article announces that Comfort has stopped answering questions about the project because of an "angry backlash" and quotes with obvious relish opponents (including Dawkins) who recommend ripping Comfort's introduction out of the book, as well as a few who suggest burning it. The site invites comments, the majority of which come from critics, then cherry-picks the most inflammatory to illustrate how "filled with hatred" atheists are.

If the true intention of Origin Into Schools is to introduce college students to creationism, Living Waters seems remarkably uninterested in finding out whether this has been achieved. It dedicates itself to presenting Comfort as assaulted by mouth-frothing atheists who advocate book-burning (just like Hitler!) but who haven't got the balls to put their ideology to the test of a public debate. Not coincidentally, another regular feature of the Living Waters site is a department called "Christian Persecution News."

What all this drama is actually designed to produce is donations, which will "expand this give-away to many more universities." The greater the heathen rage against Comfort and projects like Origin Into Schools, the deeper the faithful will dig into their pockets to support him. It's also worth noting that the more Comfort grandstands for creationism, the more essential Dawkins' combative response appears to be. (Dawkins, like Comfort, has a new book out this fall.) In a culture war that more and more comes to resemble the bouts of the World Wrestling Federation, the two have formed a relationship that could even be called symbiotic. Nature is full of bizarre survival mechanisms, as Darwin himself could surely have testified, but politics produces even stranger ones every day.

So what did Saffo actually say?

From the Sunday Times;

As the biological revolution spreads, Saffo sees many moral dilemmas ahead. For example, by using genetic testing and tailor-made drugs it may be possible to mitigate many common ailments that affect the aging population -- but such improvements will probably be available only to the super-rich.

In the future, they may be able to grow their own replacement organs, take specially designed drugs made just for them and use genetic research tools to alert them of any possible health dangers for them or their children.

"That's social dynamite," said Saffo. "I sometimes wonder if the very rich will become a completely separate species. Imagine if the very rich can live, on average, 20 years longer than the poor. That's 20 more years of earning and saving. Think what that means about wealth and power and the advantages that you pass on to your children."

I am not sure that I see exactly where the mechanism for actual "evolution" in a rigorous scientific sense come into play here. Sure, the rich will have better access to top-of-the-line medical care and they will pass on such advantages to their children. For "evolution" into a different species to occur, however, they would need to be fundamentally redesigning the genetic structure of their children, and then those children would have to mate with similarly redesigned neo-homo sapiens to pass on their new attributes. Are the super-rich capable of such coordination? Isn't it just as likely that they'll all redesign themselves in different, innovative ways, and then discover that they are biologically incompatible and incapable of reproducing? Problem solved.

But even if the super-rich did succeed in species-separation, how exactly is this news? The rich have always had better access to health care, and have always been mating with each other. The emergence of "a divide between the classes" is hardly some kind of nightmare future scenario; it is a staple of human existence since societies started hierarchically organizing themselves at the dawn of civilization. To paraphrase the apocryphal but still useful Fitzgerald retort to Hemingway: Yeah, sure, the super-rich are super-different from you and me. They have more money. And always have.

And finally, there's an easy way to avoid this dystopian future in which the descendants of Bill Gates and Lloyd Blankfein are born with immaculate complexions, huge brains, and the ability to run 40 yards in under 4.0 seconds. Tax the hell out of the rich, and use it to pay for healthcare for the rest of us neo-Neanderthals. Problem solved, again.

Celebrations and exhibitions commemorating “Origin’s" publication are gearing up across the world, but Cameron and his God squad are not going to sit around quietly while monkey ancestry gets peddled to America’s youth. On Nov. 21, they’re handing "the truth" straight to them -- in the form of 50,000 free copies of Darwin’s book, amended with a 50-page introduction refuting the whole megillah, at the top 50 college campuses across the country. Watch the promotional clip for the "Origin Into Schools" campaign here:

You can say there's inherent idiocy in the creationist worldview (you'd be right), but this is not the worst idea ever. Rather than resorting to the old tried-and-true method of simply attempting to silence evolutionary teaching, they’re leaning on the classic American standby: freedom of speech. Emphasis on the “free.”

On that rich-with-gravitas promotional clip, Cameron begins by declaring, “Our kids can no longer pray in public,” a provocative and completely inaccurate assertion, as anyone familiar with the term “public” knows. He then narrows in for the killer point: “A recent study revealed that in the top 50 universities in our country, in the fields of psychology and biology, 61 percent of the professors described themselves as atheist or agnostic.” True, though he fails to point out that the same study found only 23.4 percent of college professors overall declare themselves atheist or agnostic. College: still pretty damn godly!

But that matters not, because according to the artist formerly known as Mike Seaver, “an entire generation is being brainwashed by atheistic evolution.” He wants us to mend the “sinful heart” of our nation. Of course, plenty of people, from Darwin himself to Pope Benedict, have been able to reconcile religious beliefs with a respect for the profound elegance of science. Those people, however, didn’t star in “Left Behind,” or the highest-grossing independent film of 2008 -- a "love dare" romance called "Fireproof." That’s where Cameron's considerable star power -- and his giveaway plan -- come in.

You see, in addition to being atheistic and sinful, Darwin’s tome is also public domain. Want to run off a few thousand copies? Have at it, and get noted crackpot Ray Comfort to whip up a lively preface. Comfort is the author of “Bride of Heaven, Pride of Hell” and “End Time Believer's Bible,” a man who can be counted upon to point out “Hitler’s undeniable connection with [evolution]" and “the absence of any species-to-species transitional forms actually found in the fossil record.” (Apparently Cameron is not on the American Geological Institute’s mailing list.) Next up? Arrive at a few dozen universities, because as Cameron confidently says, “What are they going to do? Ban ‘The Origin of the Species?’ That'd be big news!”

And once those godly volunteers get on campus, what 19-year-old wouldn’t clamor for a 19th-century tract amended by someone whose argument for the evidence of God is the existence of the banana? Just to prove their point that college students will be snarfing these like Doritos, the Origin Into Schools video ends with a clip of the book recently being handed out at Cerritos College. Students walk by briskly, nonchalantly accepting the giveaway. Well, sure they do. They're college students. You should see what they'll do for a free trucker hat.

It’s easy to laugh at the absurdity of the project. It’s already being widely mined for its rich comic value, notably by a hot blond Romanian woman, who suggests maybe we get Richard Dawkins to do a new introduction to the Bible:

But what's not funny is what happens when “the opposing -- and correct -- view” gets into the hands of "our future doctors and lawyers and politicians." That's when they realize they're holding a sneaky defilement of one of the most important books ever written. Nowhere on the front of the “beautiful, full color cover edition” are the words “extremist Christian version.” Because maybe if those targeted 50,000 students knew they were getting their free book from a ministry that advises its practitioners on how to “shut up” a Jew or explain to a homosexual that he’s damned, they might not be so keen on it. They might feel duped and angry at accepting something from a group that proclaims free speech but doesn’t have the courage to put its true intentions right there on the cover.

Darwin, however, might have been amused. “I love fools’ experiments,” he once said. “I am always making them.” 

Wrangham, the Ruth B. Moore Professor of Biological Anthropology at Harvard University's Peabody Museum of Archaeology and Ethnology, began his career studying chimpanzees alongside Jane Goodall, and rose to academic acclaim as a primatologist specializing in the roots of male aggression. Naturally, he tends to think of most scientific questions in relation to chimps. And so it was that a few years ago, while sitting in front of his fireplace preparing a lecture on human evolution, he wondered, "What would it take to turn a chimpanzee-like animal into a human?" The answer, he decided, was in front of him: fire to cook food.

For years, accepted wisdom has held that it was a transition to meat eating that prompted human evolution -- which makes Wrangham's hypothesis a radical departure. Yet, the more he tested his theory, the more he found the science to back it up: Cooked food is universally easier to process and more nutritionally dense than raw food, which means adopting a cooked diet would have given man a biological advantage. The energy he once spent consuming and digesting raw food could be diverted to other physiological functions, leading to the development of bigger bodies and brains. And Wrangham's "cooking hypothesis" not only explains the physical changes that humans underwent but also the social ones: Cooking created a sexual division of labor that informs our ideas of gender, love, family and marriage even to this day. "Humans are adapted to eating cooked food in the same essential way as cows adapted to eating grass, or fleas to sucking blood," Wrangham concludes. "And the results pervade our lives, from our bodies to our minds. We humans are the cooking apes, the creatures of the flame."

Salon spoke with Wrangham, 60, by telephone from his research station in Uganda, about the dangers of strictly raw-food diets, why women are the ones who cook and the tricky business of calorie counting.

For years scientists have suggested that the making of tools, and then using tools for hunting and meat-eating, were factors that prompted the evolution of man as we know him. You push that theory farther to say that it was not eating meat, but cooking it and eating it, that's responsible for the transformation. How did you make that leap?

In the very beginning, I wasn't even thinking about human evolution. In fact, the basic idea came to me after long days of following chimpanzees, when -- because I was hungry, and sometimes I didn't take my food with me -- I tried to eat what they ate. I assumed that since I was a member of a species that was so closely related to chimps -- different only in terms of bodies and brains -- I would be able to eat anything that they could. But in actuality, though I could force it down, I quickly realized that I could not eat enough of what they ate to satisfy my hunger.

That started me subconsciously wondering about the question of food's role in human evolution. But it wasn't until some years later -- when I was sitting in front of my fireplace one night, thinking how nice and comforting a fire is, and how long ago back it would have been that our ancestors had been doing the same thing -- that I went further back in time in my mind, and realized it was very difficult to imagine our ancestors having fire and not cooking. And from there, I began to find it very hard to imagine any creature with the basic human shape surviving on raw food.

Still, when I started my research, I was amazed to discover how little investigation had been done into the nutritional and biological aspects of cooking. In particular, I was amazed by how many people thought that humans could live perfectly well on raw food.

Yes, you do quite a convincing job of arguing that a purely raw diet cannot sustain an active human. Do you believe that we have evolved to a point where a raw diet is fundamentally against our biology?

Yes, I suppose I do. If I hesitate, it is because I certainly recognize that raw foodists who live in an urban area of a well-to-do nation can make it work, so it's not that much against our biology. But I do feel very confident now that going off into the wild and living like a hunter-gatherer on raw food is not possible. People who switch to a raw diet report feeling constant hunger and lose large amounts of weight, even when they are careful to take in at least the nutritionally suggested number of calories a day for an adult. Basically, all the studies show that over the long term, a strictly raw diet cannot guarantee an adequate energy supply for our bodies. In other words, raw foodism is against our biology in a state of nature.

How do you respond to raw foodists who say a raw diet makes them feel healthier than they ever have before?

My response is that under modern conditions, living in places where you have money and grocery stores that make a super abundance of high-class domesticated foods accessible, I think it probably can be a healthy way of eating. Don't get me wrong: I have tremendous admiration for raw food devotees because it is a very hard life to resist the temptations of cooked food, and they must build their whole life around it. And of course, because they build their lives around it, they are very, very committed to the idea that it is a valuable diet. That makes them feel some resentment toward me, I guess. But the irony is that these days, very often, cooked food can be unhealthy, too. The most obvious way is that people eat too much of it.

But raw foodism seems like a pretty extreme response to the problem of obesity, doesn't it? And from what I can tell, most people don't eat raw food just to lose weight -- there seems to be a philosophical element to it, an idea that as though by choosing a raw diet, they can get back to a pure state.

Yes, of course, raw foodists argue quite strongly that it is our natural diet. My response to them is to say that yes it is, in a way. But it was natural 2 million years ago, not a few thousand years ago.

You write that cooked foods give our bodies more energy than raw foods. Can you explain that, because it seems somewhat counterintuitive. Even when you're not adding anything -- oils or fats -- the caloric value goes up?

It's really very simple. Cooking doesn't change the actual number of calories in food -- meaning that, if you take two portions of raw vegetable or animal product and cook one of them, when you blow it up in a bomb calorimeter and compare the two, you'd get the same number of calories. But there are two big things that cooking does. One is that it increases the proportion of the nutrients that our bodies digest, and from the data I reviewed -- for instance, in the case of egg protein it goes from 50 percent to 90 percent -- it looks as though that effect can make an enormous difference. And the second thing it does is that cooking reduces the costs we pay to digest our food.

So, eating cooked food conserves our energy?

That's right. We all fall asleep after a heavy meal, but if you eat a large meal of raw food, you'll fall asleep faster, because your body is working harder. More oxygen will be leaving your peripheral tissues and going to your intestinal organs.

Basically, cooking makes the food we eat more nutritionally efficient?

Yes. And that's why in my last chapter, I take on the issue of our food labeling system. When you treat food through processing or grinding, you're not actually creating more calories -- so technically, the food labeling system we have now is correct. But, if we want to be realistic about the caloric value we actually get from a food, we need to modify our labels to reflect more subtle measurements -- something like: "This item has been given a level 2 processing, which has increased its nutritional value by 50 percent."

You argue that cooking not only shaped our bodies, but it also shaped our households and our most basic ideas of gender. How so?

Well, without language, we can't be absolutely sure about what happened right in the beginning. But with what knowledge we have, I do think that cooking has this huge impact on households and our system of gender as we see it today -- and I've been trying to figure out where my thinking on this began. I've been fascinated for a long time by the idea that cooking basically produces a lump of food -- yet unlike any other primate, we humans have an extraordinary degree of respect for women who make it. Other men -- bachelors, children -- almost never take food from them. And the more I thought about this, I concluded that it looked to me like a system in which women cook for their husbands to earn the social protections that only men can give them through their membership in the male community.

So the concept of marriage began fundamentally not as about power or sex, but food?

Yes, though that would mean that women always do the cooking, and when I first started down this path, I wasn't at all sure that was the case. So, I went to the anthropological literature, and sure enough, I found reports of societies where men did the cooking. But then I dug into it more carefully -- and I discovered that, in the cases where the anthropologists claimed the men had done the cooking, the scientists had been wrong. In every single society women cook for men. And, what's more fascinating, in many societies you can really say that food or domestic promiscuity is far more serious than sexual promiscuity. In other words, it's more of a breach of social convention for a woman to feed the wrong man than it is for her to have sex with him.

Why do you think societies have evolved that way?

Because it is, and has always been, so critical for a man to be able to know that someone is going to give him a meal in the evening – because this enables him to spend the whole day doing what he wants -- doing, as it were, manly things. It's very clear from the literature on small-scale societies – and probably true even in our society today – that bachelors have a very hard time of it. They are thin, they are looked down upon by married men, they deeply desire to have a wife in order to be able to join the ranks of the elders. The problem that bachelors face is that they have to spend time during the day not simply doing things that will bring them glory -- like hunting -- but making sure they have a way of feeding themselves in the evening. And it uses up a lot of energy and time to take care of yourself.

A lot of my book has been challenging to people, but because the male-female relationship is so central to the way we think about humans, and because for so long people have tended to think about pair bonding as being about mating competition and choice of a sexual partner, this in particular has been quite a difficult theory for people to chew over.

Does that mean that, evolutionarily, men should focus on finding a wife who can cook instead of a beauty?

Yes, essentially. I know that from our perspective in the West, where we tend to focus even more than other societies on questions of sexual morality, it's rather an immoral suggestion that I'm making -- basically that men set themselves up with wives in order to have the freedom to be men, as it were -- and then go ahead and design their sexual strategy from that point on.

Now, in modern Western societies, that strategy is usually to stay with one's wife -- but not always, as we know! From the woman's point of view, the wife wants the security of knowing that she has her husband to protect her from the scrounging "others." It's not a notion of a love relationship. That's less common and more nakedly economic in many societies than in our own.

Haven't we evolved an emotional attachment to cooked food as well as a physical one? It didn't occur to me until I was reading your book, but raw foods have little scent -- yet the sense of smell is one of our most powerful senses. And elemental smells like warm vanilla or baked apples or grilled meat -- all cooked foods -- are ones that humans seem to respond to positively and universally across age and culture and place.

Absolutely, and as Proust says, smells definitely have an immense effect on our memory and our biology. But it's a complex question. When I was working on the book, I tested apes on a diet of cooked food, and they liked it spontaneously. You can understand why: The physical characteristics of cooked food have commonalities with other foods that are good for them in the wild. But the smells of cooked food are not like anything you'd find in the wild. They're really totally different -- though I admit I have no chemical data to support that. So, you might think that we have adapted to appreciating and enjoying cooked food as a result of our evolutionary history of exposure to it. But, in that case, other animals should not be adapted to like the smell of cooked food. And we simply have no data to reflect that at the moment.

Did your your studies change the way you thought about the way we should be eating?

Not really. I'd like people to be aware of how easy it is to overeat in today's world. But personally I've always been on a quasi-Mediterranean diet: lots of vegetables, some oil, not too much of anything and not much red meat. I don't think this experience changed the way I choose to eat, though frankly, if I had the courage, I might try a raw diet for a bit -- just to see how it is.

You haven't ever gone on a completely raw diet?

No, I haven't. It just seems such a social inconvenience. But maybe that's just an excuse.