Why Fire Makes Us Human
Wherever humans have gone in the world, they have carried with them two things, language and fire. As they traveled through tropical forests they hoarded the precious embers of old fires and sheltered them from downpours. When they settled the barren Arctic, they took with them the memory of fire, and recreated it in stoneware vessels filled with animal fat. Darwin himself considered these the two most significant achievements of humanity. It is, of course, impossible to imagine a human society that does not have language, but—given the right climate and an adequacy of raw wild food—could there be a primitive tribe that survives without cooking? In fact, no such people have ever been found. Nor will they be, according to a provocative theory by Harvard biologist Richard Wrangham, who believes that fire is needed to fuel the organ that makes possible all the other products of culture, language included: the human brain.在这个世界上，不管人们走到哪里，有两样东西总会伴随左右：语言和火。在穿过热带雨林时，人们会将燃烧着的珍贵木炭小心保存起来，以免被暴雨浇灭。当他们在茫茫北极定居，会随身携带着火种，然后在盛满动物脂肪的石器中重新点燃。达尔文认为它们是人类最重要的两大成就。一个没有语言的社会当然是不可想象的，但是，如果在一个气候适宜、野生食物充足的环境下，是不是一个原始部落就能够不靠烹饪而存活下去？事实上，尚未发现过有这种人存在。按照哈佛生物学家理查德·朗汉姆的挑战性理论，这种人也不可能存在，他认为，火为一种器官提供了燃料，这种器官使得包括语言在内的所有其他文化产物，成为可能，这个器官就是人的大脑。
Every animal on earth is constrained by its energy budget; the calories obtained from food will stretch only so far. And for most human beings, most of the time, these calories are burned not at the gym, but invisibly, in powering the heart, the digestive system and especially the brain, in the silent work of moving molecules around within and among its 100 billion cells. A human body at rest devotes roughly one-fifth of its energy to the brain, regardless of whether it is thinking anything useful, or even thinking at all. Thus, the unprecedented increase in brain size that hominids embarked on around 1.8 million years ago had to be paid for with added calories either taken in or diverted from some other function in the body. Many anthropologists think the key breakthrough was adding meat to the diet. But Wrangham and his Harvard colleague Rachel Carmody think that’s only a part of what was going on in evolution at the time. What matters, they say, is not just how many calories you can put into your mouth, but what happens to the food once it gets there. How much useful energy does it provide, after subtracting the calories spent in chewing, swallowing and digesting? The real breakthrough, they argue, was cooking.
地球上的每一种动物都受制于自身有限的能量；从食物中获取的卡路里只能维持一定的时间。对于大多数人类来说，多数时间里，他们所获取的卡路里并不是消耗在体育馆里，而是为心脏、消化系统，特别是大脑等提供能量，以肉眼无法察觉的形式，静静地将分子在人体的1000亿个细胞里进行着转移。当人体处在休息状态中时，不管大脑是否在思考任何有意义的事情，抑或是根本没有思考，都会将约五分之一的能量供给大脑。人脑从大约1800万年前开始变大，到现在已发展到前所未有的尺寸，因此，它需要额外补充卡路里，这些能量要么从体外摄入，要么从人体的其他功能上转移过来。许多人类学家认为，肉类进入到人类饮食中是一个关键性突破。但朗汉姆与他的同事瑞秋·卡莫迪认为，这只是当时进化过程中的一部分而已。他们说，你将多少卡路里吃下去不重要，重要的是食物在人体中所发生的变化。经过咀嚼、吞咽和消化所提取的卡路里，究竟能为人体提供多少有效能量呢？他们认为，真正的突破是人类学会了烹饪。
Wrangham, who is in his mid-60s, with an unlined face and a modest demeanor, has a fine pedigree as a primatologist, having studied chimpanzees with Jane Goodall at Gombe Stream National Park. In pursuing his research on primate nutrition he has sampled what wild monkeys and chimpanzees eat, and he finds it, by and large, repellent. The fruit of the Warburgia tree has a “hot taste” that “renders even a single fruit impossibly unpleasant for humans to ingest, ” he writes from bitter experience. “But chimpanzees can eat a pile of these fruits and look eagerly for more.” Although he avoids red meat ordinarily, he ate raw goat to prove a theory that chimps combine meat with tree leaves in their mouths to facilitate chewing and swallowing. The leaves, he found, provide traction for the teeth on the slippery, rubbery surface of raw muscle.
朗汉姆60多岁，脸上没有皱纹，看上去很谦虚，作为一名灵长类动物学家，他具有良好的背景，他曾和简·古德奥一起在贡贝溪国家公园研究过黑猩猩。在对灵长类动物营养的研究过程中，他采集了野猴和黑猩猩的食物样本，结果发现，这些食物大多非常难吃。他写道，十数樟树的果实“吃起来很辣”，“即便是一颗果实也难以下咽”，对此，他有着亲身体会。“但是黑猩猩却能吃下一堆这种果实，而且看上去还意犹未尽。”尽管平常他不吃红肉，但为了证明黑猩猩将肉和树叶搀着吃，是为了促进咀嚼和吞咽，他吃过生山羊肉。他发现，树叶能够提供摩擦力，有利于牙齿咀嚼表面光滑的橡胶状生肉。
Food is a subject on which most people have strong opinions, and Wrangham mostly excuses himself from the moral, political and aesthetic debates it provokes. Impeccably lean himself, he acknowledges blandly that some people will gain weight on the same diet that leaves others thin. “Life can be unfair, ” he writes in his 2010 book Catching Fire, and his shrug is almost palpable on the page. He takes no position on the philosophical arguments for and against a raw-food diet, except to point out that it can be quite dangerous for young children. For healthy adults, it’s “a terrific way to lose weight.”
对于食物，多数人都有着自己非常主观的看法，朗汉姆对于食物所引起的道德、政治以及美学方面的争论，基本上是避而不谈。朗汉姆本人身材瘦削，他坦然承认，同样的饮食，有人会变胖，有人则不会。“生活是不公平的，”在他2010年的作品《着火》中，他这样写道，而且他的无奈之情也是跃然纸上。除了指出生食品对于低龄儿童存在危险性外，对于支持和反对生食品的哲学争论，他并没有明确的态度。对于健康的成人，生吃食物是“很棒的减肥方法。”
Which is, in a way, his point: Human beings evolved to eat cooked food. It is literally possible to starve to death even while filling one’s stomach with raw food. In the wild, people typically survive only a few months without cooking, pollan even if they can obtain meat. Wrangham cites evidence that urban raw-foodists, despite year-round access to bananas, nuts and other high-quality agricultural products, as well as juicers, blenders and dehydrators, are often underweight. Of course, they may consider this desirable, but Wrangham considers it alarming that in one study half the women were malnourished to the point they stopped menstruating. They presumably are eating all they want, and may even be consuming what appears to be an adequate number of calories, based on standard USDA tables. There is growing evidence that these overstate, sometimes to a considerable degree, the energy that the body extracts from whole raw foods. Carmody explains that only a fraction of the calories in raw starch and protein are absorbed by the body directly via the small intestine. The remainder passes into the large bowel, where it is broken down by that organ’s ravenous population of microbes, which consume the lion’s share for themselves. Cooked food, by contrast, is mostly digested by the time it enters the colon; for the same amount of calories ingested, the body gets roughly 30 percent more energy from cooked oat, wheat or potato starch as compared to raw, and as much as 78 percent from the protein in an egg. In Carmody’s experiments, animals given cooked food gain more weight than animals fed the same amount of raw food. And once they’ve been fed on cooked food, mice, at least, seemed to prefer it.
他的观点从某种程度上来说，就是：人类将食物做熟了吃，是一个长期的发展过程。即便一个人吃下一肚子的生食物，他也完全会有可能饿死。在野外，即便能够获取到肉类，如果生吃，人们通常只能够存活几个月。朗汉姆援引证据显示，尽管一年到头能够接触到香蕉、坚果和其他优质农产品，而且还有榨汁机、搅拌器和脱水器等可以使用，城市中的生食者通常体重偏轻。当然，有人会很羡慕，但朗汉姆认为这种情况需要引起人们警惕，在一项研究中，有半数的妇女因为营养不良导致月经停止。他们可能正在吃自己想吃的食物，而且，似乎也摄入了符合美国农业部标准的足量的卡路里。不断有新的证据显示，人体从完全生的食物中所能提取的能量被过分夸大了，有时被夸大到十分惊人的程度。卡莫迪解释说，生淀粉和蛋白质中的卡路里，只有一小部分会被小肠直接吸收，剩余食物则进入到大肠中，在那里，无数饥肠辘辘的微生物会将它们分解，然后吸收掉大部分的卡路里。与此相比，熟食在进入到结肠时基本上就被消化掉了；同样的卡路里摄入量，人体从熟燕麦、小麦或马铃薯中所获取的能量，比生的要多约30%，而熟鸡蛋比生鸡蛋甚至要高出78%。在卡莫迪的实验中，用熟食喂养的动物，体重要高于用同等数量的生食所喂养的动物。一旦动物食用过熟食，它们就更愿意食用熟食，至少老鼠是这种情况。
In essence, cooking—including not only heat but also mechanical processes such as chopping and grinding—outsources some of the body’s work of digestion so that more energy is extracted from food and less expended in processing it. Cooking breaks down collagen, the connective tissue in meat, and softens the cell walls of plants to release their stores of starch and fat. The calories to fuel the bigger brains of successive species of hominids came at the expense of the energy-intensive tissue in the gut, which was shrinking at the same time—you can actually see how the barrel-shaped trunk of the apes morphed into the comparatively narrow-waisted Homo sapiens. Cooking freed up time, as well; the great apes spend four to seven hours a day just chewing, not an activity that prioritizes the intellect.
本质上来说，烹饪——不仅包括加热，还包括切割和研磨等物理加工过程——分担了人体的一部分消化工作，从而人体就可以提取更多能量，减少加工过程中所耗费的能量。烹饪使胶原蛋白、肉类中的结缔组织得到分解，还可以软化植物细胞壁，从而释放出其中所贮藏的淀粉和脂肪。随着人类科属物种大脑的不断变大，原本大量消耗能量的内脏组织，会有一部分卡路里转向供应大脑，此时内脏则不断缩小——从猿人的水桶腰到智人相对较细的腰围，你可以从这一进化过程中看出究竟。烹调还可以节省时间；猿人每天光咀嚼就要花4到7个小时的时间，而咀嚼并不是智人所关心的首要问题。
The trade-off between the gut and the brain is the key insight of the “expensive tissue hypothesis, ” proposed by Leslie Aiello and Peter Wheeler in 1995. Wrangham credits this with inspiring his own thinking—except that Aiello and Wheeler identified meat-eating as the driver of human evolution, while Wrangham emphasizes cooking. “What could be more human, ” he asks, “than the use of fire?”
莱斯利·埃罗和皮特·维勒在1997年提出了“昂贵组织假说”，这一理论的核心见解在于能量在内脏和大脑之间的转移。朗汉姆认为这一理论为他自己的思想赋予了灵感，不过，埃罗和维勒认为食肉为人类的进化提供了动力，而朗汉姆则强调烹饪的作用。“有什么比使用火更能凸显出人性呢？”他问道。
Unsurprisingly, Wrangham’s theory appeals to people in the food world. “I’m persuaded by it, ” says Michael Pollan, author of Cooked, whose opening chapter is set in the sweltering, greasy cookhouse of a whole-hog barbecue joint in North Carolina, which he sets in counterpoint to lunch with Wrangham at the Harvard Faculty Club, where they each ate a salad. “Claude Lévi-Strauss, Brillat-Savarin treated cooking as a metaphor for culture, ” Pollan muses, “but if Wrangham is right, it’s not a metaphor, it’s a precondition.” (Read about what it's like to have dinner with Pollan)
不出意外，朗汉姆的理论引起了食品界的兴趣。“它说服了我，”《烹饪》一书的作者麦克尔·博伦说。这本书的开篇一章，发生在北卡莱罗纳一家烤全猪店中炙热而油腻的厨房里，这与他和朗汉姆在哈佛教工俱乐部所吃的一顿午餐形成了对比，当时他们各吃了一道沙拉。“克劳德·李维·斯特劳斯与布里亚·萨瓦兰将文化喻做烹饪，”博伦若有所思的说，“但假如朗汉姆是对的，那烹饪就不是文化的象征，而是文化的前提。”
Wrangham, with his hard-won experience in eating like a chimpanzee, tends to assume that—with some exceptions such as fruit—cooked food tastes better than raw. But is this an innate mammalian preference, or just a human adaptation? Harold McGee, author of the definitive On Food and Cooking, thinks there’s an inherent appeal in the taste of cooked food, especially so-called Maillard compounds. These are the aromatic products of the reaction of amino acids and carbohydrates in the presence of heat, responsible for the tastes of coffee and bread and the tasty brown crust on a roast. “When you cook food you make its chemical composition more complex, ” McGee says. “What’s the most complex natural, uncooked food? Fruit, which is produced by plants specifically to appeal to animals. I used to think it would be interesting to know if humans are the only animals that prefer cooked food, and now we’re finding out it’s a very basic preference.”
通过模仿黑猩猩的饮食，朗汉姆获得了来之不易的体会，他倾向于假定熟食比生食要好吃，但有些水果例外。但这是哺乳动物的一种内在倾向，还是人类顺应变化的结果？哈罗德·麦基是权威著作《论食物和烹饪》一书的作者，他认为烹饪过的食物，其味道具有一种内在的吸引力，特别是含有所谓的美拉德化合物。加热使氨基酸和碳水化合物发生反应，产生出这种芳香物质，这些物质为咖啡和烤面包的棕色外皮提供了诱人的色泽和可口的味道。“烹饪使食物的化学成分更加复杂，”麦基说。“最复杂的、未经烹饪的天然食物是什么？是水果，它是植物为吸引动物而专门制造出来的。我原来一直想，如果人类是唯一一种偏爱熟食的动物的话，那将非常有趣，现在，我们发现这是一种非常基本的偏好。”
Among Wrangham’s professional peers, his theory elicits skepticism, mainly because it implies that fire was mastered around the time Homo erectus appeared, roughly 1.8 million years ago. Until recently, the earliest human hearths were dated to about 250, 000 B.C.; last year, however, the discovery of charred bone and primitive stone tools in a cave in South Africa tentatively pushed the time back to roughly one million years ago, closer to what Wrangham’s hypothesis demands but still short. He acknowledges that this is a problem for his theory. But the number of sites dating from that early period is small, and the evidence of fire might not have been preserved. Future excavations, he hopes, will settle the issue.
朗汉姆的理论在他的同行中引发了怀疑，主要是他的理论暗示，大约1800万年前，直立人出现时，就已经掌握了火的使用。不久之前，人类所发现的最早的灶台还是在25万年前；然而去年，在南非的一个洞穴里，人们发现了烧焦的骨头和原始石器，这将之前的时间又暂时往前推移到大约100万年前，这一时间已接近、但仍未达到朗汉姆假说的时间要求。他承认，这是他理论中所存在的一个问题。但是那个时间的遗址数量很少，使用过火的证据可能未能保存下来。他希望未来的挖掘会解决这一问题。
In Wrangham’s view, fire did much more than put a nice brown crust on a haunch of antelope. Fire detoxifies some foods that are poisonous when eaten raw, and it kills parasites and bacteria. Again, this comes down to the energy budget. Animals eat raw food without getting sick because their digestive and immune systems have evolved the appropriate defenses. Presumably the ancestors of Homo erectus—say, Australopithecus—did as well. But anything the body does, even on a molecular level, takes energy; by getting the same results from burning wood, human beings can put those calories to better use in their brains. Fire, by keeping people warm at night, made fur unnecessary, and without fur hominids could run farther and faster after prey without overheating. Fire brought hominids out of the trees; by frightening away nocturnal predators, it enabled Homo erectus to sleep safely on the ground, which was part of the process by which bipedalism (and perhaps mind-expanding dreaming) evolved. By bringing people together at one place and time to eat, fire laid the groundwork for pair bonding and, indeed, for human society.
朗汉姆认为，火所能做的不仅仅是在鹿腿肉上烤出诱人的棕色外皮，火能将有些生食物中的毒素排除掉，而且可以杀死寄生虫和细菌。还是那句老话，人体的能量有限。动物生吃食物不会得病，因为它们已经进化出了适当的消化和免疫系统。直立人的祖先——南方古猿，或许也有这些防护系统。但人体的一举一动，即便是一个分子的移动，都需要能量；通过燃烧木头来获取相同的结果，人类就可以将这些能量更好的用于大脑。夜里，人类用火取暖，不用再穿毛皮，脱去了毛皮，人类祖先在狩猎时就可以跑的更远、更快而不至于感到太热。火让人类祖先走出了丛林，直立人用火将夜间猎食的野兽吓跑，从而可以安然入睡，这是人类祖先直立行走（或许还有扩展意识的梦）的进化过程的一部分。火将人类聚到一起，共同进餐，从而为配偶关系、乃至人类社会的形成奠定了基础。
We will now, in the spirit of impartiality, acknowledge all the ways in which cooking is a terrible idea. The demand for firewood has denuded forests. As Bee Wilson notes in her new book, Consider the Fork, the average open cooking fire generates as much carbon dioxide as a car. Indoor smoke from cooking causes breathing problems, and heterocyclic amines from grilling or roasting meat are carcinogenic. Who knows how many people are burned or scalded, or cut by cooking utensils, or die in cooking-related house fires? How many valuable nutrients are washed down the sink along with the water in which vegetables were boiled? Cooking has given the world junk food, 17-course tasting menus at restaurants where you have to be a movie star to get a reservation, and obnoxious, overbearing chefs berating their sous-chefs on reality TV shows. Wouldn’t the world be a better place without all that?
现在，为公平起见，我们承认，从许多方面来看，烹饪都是个糟糕的主意。对柴火的需求使得森林遭到砍伐。正如比·威尔逊在她的新书《餐叉的思考》中所提到的，露天做饭所生的火，平均所制造的二氧化碳和汽车一样多。室内烹饪所产生的烟导致呼吸道疾病，烧烤肉类会产生致癌的杂环胺。天晓得到底有多少人被烧伤、烫伤，被厨具割伤，以及死于做饭所引起的火灾？有多少有价值的营养随着菜汤流进了污水池？烹饪为这个世界带来了垃圾食品，还有17道菜的大餐（你得是个电影明星才能在做这些菜的餐馆里订到位子），以及可恶、跋扈的大厨在电视真人秀上训斥着他的助手。所有这些统统消失，这个世界是否会变得更好?
Raw-food advocates are perfectly justified in eating what makes them feel healthy or morally superior, but they make a category error when they presume that what nourished Australopithecus should be good enough for Homo sapiens. We are, of course, animals, but that doesn’t mean we have to eat like one. In taming fire, we set off on our own evolutionary path, and there is no turning back. We are the cooking animal.
生食倡导者完全有理由，享用那些让他们觉得健康和更高尚的食物，但如果他们认为，那些对南方古猿有好处的食物同样对智人有好处，那他们就是犯了一个范畴上的错误。我们当然是动物，但这并不代表着我们一定要像动物一样进食。在驯服火的过程中，我们踏上了自己的进化之路，而且已无法回头，我们是烹饪动物。
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