CHAPTER 7

第七章

HOW TO MAKE AN ALMOND

怎样识别杏仁

IF YOU'RE A HIKER WHOSE APPETITE IS JADED BY FARM-grown foods, it's fun to try eating wild foods. You know that some wild plants, such as wild strawberries and blueberries, are both tasty and safe to eat. They're sufficiently similar to familiar crops that you can easily recognize the wild berries, even though they're much smaller than those we grow. Adventurous hikers cautiously eat mushrooms, aware that many species can kill us. But not even ardent nut lovers eat wild almonds, of which a few dozen contain enough cyanide ^{(the poison used in Nazi gas chambers)} to kill us. The forest is full of many other plants deemed inedible.

如果你是一个徒步旅行者，吃腻了农场上种植的瓜果蔬菜，那么试一试吃一点野生食物，就是一件有趣的事。你知道，有些野生植物，如野草莓和乌饭树的蓝色浆果，不但味道好，而且吃起来安全。它们的样子同我们所熟悉的农家品种相当类似，所以我们能够很容易地把这些野生浆果认出来，虽然它们比我们种植的那些品种要小得多。爱冒险的徒步旅行者在吃蘑菇时小心翼翼，因为他们知道蘑菇中有许多品种吃了会致人死命。但即使是最爱吃干果的人也不会去吃野生的杏仁，因为其中有几十种含有足以致人死命的氰化物^{(即纳粹毒气室中使用的那种毒物)}。森林中到处都有其他许多被认为不能吃的植物。

Yet all crops arose from wild plant species. How did certain wild plants get turned into crops? That question is especially puzzling in regard to the many crops ^{(like almonds)} whose wild progenitors are lethal or bad-tasting, and to other crops ^{(like corn)} that look drastically different from their wild ancestors. What cavewoman or caveman ever got the idea of “domesticating” a plant, and how was it accomplished?

然而，所有的作物都来自野生植物。某些野生植物是怎样变成作物的呢？这是一个特别令人困惑的问题，因为许多作物^{(如巴旦杏)}的祖先不是吃了叫人送命就是味道糟得难以入口，而其他一些作物^(如玉米)在外观上同它们的野生祖先又差别太大。住在岩洞里的那些男女是些什么样的人，竟会想出“驯化”植物这个主意来？而这又是如何做到的呢？

Plant domestication may be defined as growing a plant and thereby, consciously or unconsciously, causing it to change genetically from its wild ancestor in ways making it more useful to human consumers. Crop development is today a conscious, highly specialized effort carried out by professional scientists. They already know about the hundreds of existing crops and set out to develop yet another one. To achieve that goal, they plant many different seeds or roots, select the best progeny and plant their seeds, apply knowledge of genetics to develop good varieties that breed true, and perhaps even use the latest techniques of genetic engineering to transfer specific useful genes. At the Davis campus of the University of California, an entire department ^{(the Department of Pomology)} is devoted to apples and another ^{(the Department of Viticulture and Enology)} to grapes and wine.

植物驯化可以定义为：栽种某一植物并由此有意或无意地使其发生不同于其野生祖先的、更有利于人类消费的遗传变化。对作物的培育在今天是一种由专业科学家去做的、自觉的、高度专业化的工作。他们已经了解现存的数以百计的作物，并着手开发新的品种。为了实现这一目标，他们种下了许多种子或根，选出最好的后代，再种下它们的种子，把遗传学知识用来培育能够繁殖纯种的优良品种，也许甚至会利用最新的遗传工程技术来转移某些有用的基因。加利福尼亚大学戴维斯分校有一个系^{(果树栽培学系)}，全系专门研究苹果，还有一个系^{(葡萄栽培与葡萄酒工艺学系)}，专门研究葡萄和葡萄酒。

But plant domestication goes back over 10,000 years. Early farmers surely didn't use molecular genetic techniques to arrive at their results. The first farmers didn't even have any existing crop as a model to inspire them to develop new ones. Hence they couldn't have known that, whatever they were doing, they would enjoy a tasty treat as a result.

但是，植物驯化的历史可以追溯到1万多年前。最早的农民当然不会利用分子遗传技术来得到这种结果。这些最早的农民甚至没有任何现存的作物可以作为样品来启发他们去培育新的作物品种。因此，他们不可能知道，不管他们做什么，他们最终都能一饱口福。

How, then, did early farmers domesticate plants unwittingly? For example, how did they turn poisonous almonds into safe ones without knowing what they were doing? What changes did they actually make in wild plants, besides rendering some of them bigger or less poisonous? Even for valuable crops, the times of domestication vary greatly: for instance, peas were domesticated by 8000 B.C., olives around 4000 B.C., strawberries not until the Middle Ages, and pecans not until 1846. Many valuable wild plants yielding food prized by millions of people, such as oaks sought for their edible acorns in many parts of the world, remain untamed even today. What made some plants so much easier or more inviting to domesticate than others? Why did olive trees yield to Stone Age farmers, whereas oak trees continue to defeat our brightest agronomists?

那么，最初的农民是怎样在不知不觉中驯化了植物的呢？比方说，他们是怎样在不知道自己在做什么的情况下把有毒的杏仁变成了无毒的杏仁的呢？除了使某些野生植物变得更大或毒性更少外，他们实际上还使它们产生了哪些变化呢？即使是一些重要的作物，驯化的时间也大不相同：例如，豌豆驯化的时间不迟于公元前8000年，橄榄在公元前4000年左右，草莓要等到中世纪，美洲山核桃则更迟至1846年。许多能出产食物的重要的野生植物为千百万人所珍视，例如在世界上的许多地方，人们为了得到可吃的橡实而寻找橡树，但橡树甚至在今天也仍然没有驯化。是什么使得某些植物比其他植物更容易驯化，或更吸引人去对其驯化？为什么橄榄树向石器时代的农民屈服了，而橡树则仍然使我们最聪明的农艺师一筹莫展呢？

LET'S BEGIN BY looking at domestication from the plant's point of view. As far as plants are concerned, we're just one of thousands of animal species that unconsciously “domesticate” plants.

让我们首先从植物的观点来看一看驯化的问题。就植物来说，我们不过是无意间“驯化”了植物的成千上万种的动物之一。

Like all animal species ^{(including humans)}, plants must spread their offspring to areas where they can thrive and pass on their parents' genes. Young animals disperse by walking or flying, but plants don't have that option, so they must somehow hitchhike. While some plant species have seeds adapted for being carried by the wind or for floating on water, many others trick an animal into carrying their seeds, by wrapping the seed in a tasty fruit and advertising the fruit's ripeness by its color or smell. The hungry animal plucks and swallows the fruit, walks or flies off, and then spits out or defecates the seed somewhere far from its parent tree. Seeds can in this manner be carried for thousands of miles.

和其他所有动物^(包括人)一样，植物必须将其子代向它们能够茁壮生长的地区扩散，并传递其亲代的基因。小动物的扩散靠行走或飞翔，但植物没有这样的选择自由，因此它们必须以某种方式沿途搭便车旅行。有几种植物的种子生得便于被风吹走或在水上漂流，而其他许多植物则把种子包在好吃的果子里并用颜色和气味来宣告果子的成熟，从而哄骗动物把种子带走。饥饿的动物把这果子扯下来吃掉，或者走开，或者飞走，然后在远离亲代树的某个地方把种子吐出或随粪便排出。种子可以用这种办法被带到几千英里之外。

It may come as a surprise to learn that plant seeds can resist digestion by your gut and nonetheless germinate out of your feces. But any adventurous readers who are not too squeamish can make the test and prove it for themselves. The seeds of many wild plant species actually must pass through an animal's gut before they can germinate. For instance, one African melon species is so well adapted to being eaten by a hyena-like animal called the aardvark that most melons of that species grow on the latrine sites of aardvarks.

植物的种子连你的肠胃都无法消化，而且仍然能够从你的排泄物中发出芽来，了解到这一点，你也许会感到惊奇。但任何爱冒险的而又不太容易呕吐的读者不妨做一做这方面的试验，亲自来验证一下。许多野生植物的种子实际上必须通过动物的肠胃，然后才能发芽。例如，非洲有一种瓜很容易被一种形似鬣狗的叫做土狼的动物吃掉，结果这种瓜大多数都生长在土狼排泄的地方。

As an example of how would-be plant hitchhikers attract animals, consider wild strawberries. When strawberry seeds are still young and not yet ready to be planted, the surrounding fruit is green, sour, and hard. When the seeds finally mature, the berries turn red, sweet, and tender. The change in the berries' color serves as a signal attracting birds like thrushes to pluck the berries and fly off, eventually to spit out or defecate the seeds.

关于想要沿途搭便车旅行的植物是怎样吸引动物的这个问题，可以考虑一下野草莓的例子。当草莓的种子还没有成熟、不能马上播种时，周围的果实是又青又酸又硬。当种子最后成熟时，果实就变得又红又甜又嫩。果实颜色的变化成了一种信号，把鸫一类的鸟儿吸引来啄食果实然后飞走，最后吐出或随粪便排泄出种子。

Naturally, strawberry plants didn't set out with a conscious intent of attracting birds when, and only when, their seeds were ready to be dispersed. Neither did thrushes set out with the intent of domesticating strawberries. Instead, strawberry plants evolved through natural selection. The greener and more sour the young strawberry, the fewer the birds that destroyed the seeds by eating berries before the seeds were ready; the sweeter and redder the final strawberry, the more numerous the birds that dispersed its ripe seeds.

当然，草莓并不是有意要在种子准备好撒播的时候去招引鸟儿。鸫也不是有意要去驯化草莓。相反，草莓是通过自然选择来演化的。未成熟草莓的颜色越青和味道越酸，在种子成熟前来吃草莓从而使种子遭到破坏的鸟儿就越少；成熟草莓的味道越甜和颜色越红，来撒播成熟种子的鸟儿就越多。

Countless other plants have fruits adapted to being eaten and dispersed by particular species of animals. Just as strawberries are adapted to birds, so acorns are adapted to squirrels, mangos to bats, and some sedges to ants. That fulfills part of our definition of plant domestication, as the genetic modification of an ancestral plant in ways that make it more useful to consumers. But no one would seriously describe this evolutionary process as domestication, because birds and bats and other animal consumers don't fulfill the other part of the definition: they don't consciously grow plants. In the same way, the early unconscious stages of crop evolution from wild plants consisted of plants evolving in ways that attracted humans to eat and disperse their fruit without yet intentionally growing them. Human latrines, like those of aardvarks, may have been a testing ground of the first unconscious crop breeders.

其他无数的植物都有适合于让某些种类的动物吃并撒播的果实。正如草莓适合于鸟儿一样，橡实适合于松鼠，芒果适合于蝙蝠，某些莎草适合于蚂蚁。这符合我们关于植物驯化的部分定义，因为祖代植物在遗传方面的变化使它更有利于人类消费。但没有人会一本正经地把这种演化过程称为驯化，因为鸟儿、蝙蝠和其他动物不符合那个定义的另一部分：它们不是有意去栽种植物的。同样，作物从野生植物开始演化的早期无意识阶段包括这样的一些演化方式，即植物吸引人类去采食并撒播它们的果实，但还不是有意去栽种它们。人类的排泄处所和土狼的一样，也许就是最早的无意识的作物培育者的一个试验场。

LATRINES ARE MERELY one of the many places where we accidentally sow the seeds of wild plants that we eat. When we gather edible wild plants and bring them home, some spill en route or at our houses. Some fruit rots while still containing perfectly good seeds, and gets thrown out uneaten into the garbage. As parts of the fruit that we actually take into our mouths, strawberry seeds are tiny and inevitably swallowed and defecated, but other seeds are large enough to be spat out. Thus, our spittoons and garbage dumps joined our latrines to form the first agricultural research laboratories.

我们在许多地方偶然地播下了我们所吃的植物的种子，我们的排泄处仅仅是其中之一。当我们采集到可吃的野生植物并把它们带回家的时候，有些在路上或家里散落了。有些水果在种子还仍然十分完好的时候就腐烂了，于是就被扔进了垃圾堆，不再吃它。草莓的种子是果实的一部分，实际上也被我们送入口中，但由于种子太小，最后还是被吞了下去，并随粪便排了出来。但还有些水果的种子相当大，就被吐了出来。因此，我们的茅坑加上我们的痰盂和垃圾堆一起构成了最好的农业研究实验室。

At whichever such “lab” the seeds ended up, they tended to come from only certain individuals of edible plants—namely, those that we preferred to eat for one reason or another. From your berry-picking days, you know that you select particular berries or berry bushes. Eventually, when the first farmers began to sow seeds deliberately, they would inevitably sow those from the plants they had chosen to gather, even though they didn't understand the genetic principle that big berries have seeds likely to grow into bushes yielding more big berries.

不管这些种子最后到了哪个“实验室”，它们都是来自某种可吃的植物——即我们出于某种原因喜欢吃的植物。从你采摘浆果的那些日子起，你就知道挑选某些浆果或浆果灌木。最后，当最初的农民开始有意识地去播种时，他们播下的必然是他们存心采集的那些植物的种子，虽然他们还不懂大浆果的种子有望长成能够结出更多大浆果的灌木这一遗传原则。

So, when you wade into a thorny thicket amid the mosquitoes on a hot, humid day, you don't do it for just any strawberry bush. Even if unconsciously, you decide which bush looks most promising, and whether it's worth it at all. What are your unconscious criteria?

因此，当你在一个炎热、潮湿的日子里艰难地走进到处都是蚊子的多刺的灌木丛中时，你并非只是为了任何一丛草莓才这样去做的。即使是无意识的，你还是决定了哪一丛草莓看上去最有希望，以及它是否值得你来这一趟。你的潜意识中的判断标准是什么？

One criterion, of course, is size. You prefer large berries, because it's not worth your while to get sunburned and mosquito bitten for some lousy little berries. That provides part of the explanation why many crop plants have much bigger fruits than their wild ancestors do. It's especially familiar to us that supermarket strawberries and blueberries are gigantic compared with wild ones; those differences arose only in recent centuries.

一个判断标准当然就是大小。你喜欢大的浆果，因为你不值得为几颗难看的小浆果去被太阳晒烤和蚊子叮咬。这就是许多作物的果实比它们野生祖先的果实大得多的部分原因。超市里的草莓和乌饭树的蓝色浆果同野生的品种相比显得硕大肥壮，这情形是我们特别熟悉的；这方面的差异也只是最近几百年才出现的。

Such size differences in other plants go back to the very beginnings of agriculture, when cultivated peas evolved through human selection to be 10 times heavier than wild peas. The little wild peas had been collected by hunter-gatherers for thousands of years, just as we collect little wild blueberries today, before the preferential harvesting and planting of the most appealing largest wild peas—that is, what we call farming—began automatically to contribute to increases in average pea size from generation to generation. Similarly, supermarket apples are typically around three inches in diameter, wild apples only one inch. The oldest corn cobs are barely more than half an inch long, but Mexican Indian farmers of A.D. 1500 already had developed six-inch cobs, and some modern cobs are one and a half feet long.

在其他植物方面的这种大小差异，可以追溯到农业出现的初期，那时人工栽培的豌豆经过筛选和演化，其重量超过野生豌豆的10倍。狩猎采集族群在几千年里采集的就是这种小小的野生豌豆，就像我们今天采集乌饭树的蓝色浆果一样。然后，他们才有选择地去收获和种植那些最吸引人的最大的野生豌豆——这就是我们所说的农业——它开始自动地促使豌豆的平均大小每一代都有增加。同样，超市里的苹果的直径一般在3英寸左右，而野生苹果的直径只有1英寸。最早的玉米棒子的长度几乎不超过半英寸，但公元1500年墨西哥印第安农民已经培育出长达6英寸的玉米棒子，而现代的玉米棒子则可长达一英尺半。

Another obvious difference between seeds that we grow and many of their wild ancestors is in bitterness. Many wild seeds evolved to be bitter, bad-tasting, or actually poisonous, in order to deter animals from eating them. Thus, natural selection acts oppositely on seeds and on fruits. Plants whose fruits are tasty get their seeds dispersed by animals, but the seed itself within the fruit has to be bad-tasting. Otherwise, the animal would also chew up the seed, and it couldn't sprout.

我们所栽种的植物的种子和它们的许多野生祖先的种子的另一个明显的差异是在味苦方面。许多野生植物的种子为防动物把它们吃掉，在演化过程中味道变苦而难以入口，或竟然有毒。因此，自然选择对种子和果实所起的作用正好相反。果实好吃的植物让动物来撒播它们的种子，但果实里的种子必须很难吃。否则，动物就会把种子嚼碎，种子也就发不出芽来了。

Almonds provide a striking example of bitter seeds and their change under domestication. Most wild almond seeds contain an intensely bitter chemical called amygdalin, which ^{(as was already mentioned)} breaks down to yield the poison cyanide. A snack of wild almonds can kill a person foolish enough to ignore the warning of the bitter taste. Since the first stage in unconscious domestication involves gathering seeds to eat, how on earth did domestication of wild almonds ever reach that first stage?

关于苦味的种子及其在驯化过程中的变化，杏仁提供了一个引人注目的例子。大多数野巴旦杏的种子都含有一种叫做苦杏仁苷的其苦无比的化学物质，这种物质^{(前面已提到过)}在分解时产生了有毒的氰化物。如果有人竟会蠢到不顾野生杏仁苦味的警告而去吃它，那他就会因此而丧命。既然无意识驯化的第一阶段是采集可以吃的种子，那么对野生杏仁的驯化又是怎样达到这第一阶段的呢？

The explanation is that occasional individual almond trees have a mutation in a single gene that prevents them from synthesizing the bitter-tasting amygdalin. Such trees die out in the wild without leaving any progeny, because birds discover and eat all their seeds. But curious or hungry children of early farmers, nibbling wild plants around them, would eventually have sampled and noticed those nonbitter almond trees. ^{(In the same way, European peasants today still recognize and appreciate occasional individual oak trees whose acorns are sweet rather than bitter.)} Those nonbitter almond seeds are the only ones that ancient farmers would have planted, at first unintentionally in their garbage heaps and later intentionally in their orchards.

对此的解释是：偶然有几棵巴旦杏树在一个基因上产生了突变，使它们不能合成苦味的苦杏仁苷。这些树在荒野里灭绝了，没有留下任何后代，因为鸟儿发现了它们的种子，把种子吃个精光。但最初的农民的孩子们由于好奇或饥饿，把他们周围的野生植物每一种都弄一点来尝尝，最后竟品尝到并发现了这些没有苦味的巴旦杏树。^{(同样，如果今天的欧洲农民偶然发现了几棵橡实甜而不苦的橡树，他们仍然会感到庆幸。)}这些不苦的巴旦杏的种子就是古代农民可能会去种的种子，开头是无心地任其生长在垃圾堆上，后来则是有意地种在自己的果园里了。

Already by 8000 B.C. wild almonds show up in excavated archaeological sites in Greece. By 3000 B.C. they were being domesticated in lands of the eastern Mediterranean. When the Egyptian king Tutankhamen died, around 1325 B.C., almonds were one of the foods left in his famous tomb to nourish him in the afterlife. Lima beans, watermelons, potatoes, eggplants, and cabbages are among the many other familiar crops whose wild ancestors were bitter or poisonous, and of which occasional sweet individuals must have sprouted around the latrines of ancient hikers.

不迟于公元前8000年的野生杏仁，已在发掘出来的希腊考古遗址中出现。到公元前3000年，在地中海以东的土地上已有野生杏仁在驯化。埃及国王图坦卡蒙^[1]于公元前1325年左右去世后，放在他的著名陵墓里供他死后享用的食品中就有杏仁。在其他许多为人们所熟悉的作物中有利马豆、西瓜、马铃薯、茄子和卷心菜。这些作物的野生祖先，有的味苦，有的有毒，其中偶然也有几个味道甘美的品种，但那必定是从古代旅行者的排泄处长出来的。

While size and tastiness are the most obvious criteria by which human hunter-gatherers select wild plants, other criteria include fleshy or seedless fruits, oily seeds, and long fibers. Wild squashes and pumpkins have little or no fruit around their seeds, but the preferences of early farmers selected for squashes and pumpkins consisting of far more flesh than seeds. Cultivated bananas were selected long ago to be all flesh and no seed, thereby inspiring modern agricultural scientists to develop seedless oranges, grapes, and watermelons as well. Seedlessness provides a good example of how human selection can completely reverse the original evolved function of a wild fruit, which in nature serves as a vehicle for dispersing seeds.

如果说大小和味道是狩猎采集族群选择野生植物的最明显的标准，那么其他标准则包括果实肉多或无子、种子含油多以及纤维长。野南瓜种子外面的果肉很少，或根本没有果肉，但早期的农民喜欢选择果肉比种子多得多的南瓜。很久以前，人们在栽培香蕉时就选择了全是肉而没有种子的品种，从而启发了现代农业科学家去培育无籽柑橘、无籽葡萄和无籽西瓜。水果无籽是一个很好的例子，说明人类的选择是怎样把野生水果原来的演化作用完全颠倒了过来，因为原来的演化作用实际上只是撒播种子的一种手段。

In ancient times many plants were similarly selected for oily fruits or seeds. Among the earliest fruit trees domesticated in the Mediterranean world were olives, cultivated since around 4000 B.C. for their oil. Crop olives are not only bigger but also oilier than wild ones. Ancient farmers selected sesame, mustard, poppies, and flax as well for oily seeds, while modern plant scientists have done the same for sunflower, safflower, and cotton.

在古代，有许多植物都是由于含油的果实和种子而同样得到选择的。在地中海地区最早得到驯化的果树有油橄榄，栽培的时间大约在公元前4000年以后，栽培的目的就是为了得到它的油。人工栽培的油橄榄比野生的油橄榄不但果实大，而且含油率也高。古代农民为了得到含油的种子而选择了芝麻、芥菜、罂粟和亚麻，而现代的植物学家为了同样的目的而选择了向日葵、红花和棉花。

Before that recent development of cotton for oil, it was of course selected for its fibers, used to weave textiles. The fibers ^{(termed lint)} are hairs on the cotton seeds, and early farmers of both the Americas and the Old World independently selected different species of cotton for long lint. In flax and hemp, two other plants grown to supply the textiles of antiquity, the fibers come instead from the stem, and plants were selected for long, straight stems. While we think of most crops as being grown for food, flax is one of our oldest crops ^{(domesticated by around 7000 B.C.)}. It furnished linen, which remained the chief textile of Europe until it became supplanted by cotton and synthetics after the Industrial Revolution.

为了油而培育棉花，这还是近代的事。在这之前，当然是为了纺织用的纤维而选择棉花。棉花的纤维^{(或称棉绒)}是棉花种子上的茸毛，美洲和旧大陆的早期农民为了得到长的棉绒独立地选择了不同品种的棉花。另外还有两种作为古代纺织品原料而栽种的植物是亚麻和大麻，它们的纤维来自茎，因此对它们的选择标准是又长又直的茎。虽然我们把大多数作物看作是为吃而种植的，但亚麻也是我们最早的作物之一^{(驯化时间不迟于公元前7000年)}。它是亚麻布的原料，它一直是欧洲主要的纺织原料，直到工业革命后为棉花和合成纤维所代替。

SO FAR, ALL the changes that I've described in the evolution of wild plants into crops involve characters that early farmers could actually notice—such as fruit size, bitterness, fleshiness, and oiliness, and fiber length. By harvesting those individual wild plants possessing these desirable qualities to an exceptional degree, ancient peoples unconsciously dispersed the plants and set them on the road to domestication.

迄今为止，我们对野生植物演化为作物所描述的种种变化，与早期农民实际上可能已注意到的一些特征直接有关——如果实的大小、苦味、多肉、含油和纤维的长度。通过收获这些具有特别可取的品质的野生植物，古代人在无意识中传播了这些植物，使它们走上了驯化之路。

In addition, though, there were at least four other major types of change that did not involve berry pickers making visible choices. In these cases the berry pickers caused changes either by harvesting available plants while other plants remained unavailable for invisible reasons, or by changing the selective conditions acting on plants.

然而，除此以外，至少还有其他4种主要变化未能引起采摘浆果的人去作出引人注目的选择。在这些情况下，如果采摘浆果的人的确引起了什么变化，那或是由于其他植物因某些不明原因始终无法得到而收获了可以得到的植物，或是由于改变了对植物起作用的选择条件。

The first such change affected wild mechanisms for the dispersal of seeds. Many plants have specialized mechanisms that scatter seeds ^{(and thereby prevent humans from gathering them efficiently)}. Only mutant seeds lacking those mechanisms would have been harvested and would thus have become the progenitors of crops.

第一个这样的改变影响了种子传播的野生结构。许多植物都有其传播种子的专门机制^{(从而使人类无法对它们进行有效的采集)}。只有由突变产生的缺乏这种结构的种子才会被人收获而成为作物的祖先。

A clear example involves peas, whose seeds ^{(the peas we eat)} come enclosed in a pod. Wild peas have to get out of the pod if they are to germinate. To achieve that result, pea plants evolved a gene that makes the pod explode, shooting out the peas onto the ground. Pods of occasional mutant peas don't explode. In the wild the mutant peas would die entombed in their pod on their parent plants, and only the popping pods would pass on their genes. But, conversely, the only pods available to humans to harvest would be the nonpopping ones left on the plant. Thus, once humans began bringing wild peas home to eat, there was immediate selection for that single-gene mutant. Similar nonpopping mutants were selected in lentils, flax, and poppies.

一个明显的例子就是豌豆。豌豆的种子^{(我们吃的豌豆)}封闭在豆荚里。野豌豆要发芽生长，就必须破荚而出。为了做到这一点，豌豆就演化出一种基因，能使豆荚突然破裂，把豌豆弹射到地上。偶然产生突变的豌豆的豆荚不会爆裂。在野外，这种产生突变的豌豆一直到死都是包裹在亲株上的豆荚里面，而只有这种能爆裂的豆荚才把它们的基因传递给后代。但与此相反的是，人类能够收获到的唯一豆荚可能就是留在植株上的那些不爆裂的豆荚。因此，一旦人类开始把野豌豆带回家去吃，立刻就产生了对这种单基因突变的选择。对同样不爆裂突变进行选择的例子还有兵豆、亚麻和罂粟。

Instead of being enclosed in a poppable pod, wild wheat and barley seeds grow at the top of a stalk that spontaneously shatters, dropping the seeds to the ground where they can germinate. A single-gene mutation prevents the stalks from shattering. In the wild that mutation would be lethal to the plant, since the seeds would remain suspended in the air, unable to germinate and take root. But those mutant seeds would have been the ones waiting conveniently on the stalk to be harvested and brought home by humans. When humans then planted those harvested mutant seeds, any mutant seeds among the progeny again became available to the farmers to harvest and sow, while normal seeds among the progeny fell to the ground and became unavailable. Thus, human farmers reversed the direction of natural selection by 180 degrees: the formerly successful gene suddenly became lethal, and the lethal mutant became successful. Over 10,000 years ago, that unconscious selection for nonshattering wheat and barley stalks was apparently the first major human “improvement” in any plant. That change marked the beginning of agriculture in the Fertile Crescent.

野生的小麦和大麦不是封闭在能够爆裂的荚子里，而是长在麦秆的顶端，麦秆能自动脱落，使种子落到能够发芽生长的地面上。一种单基因突变使麦秆不会脱落。在野生状态下，这种突变对植物来说可能是毁灭性的，因为种子不能落地，就无法发芽生根。但这些产生突变的种子省力地留在秆子上可能是在等待人类来收获它们并把它们带回家。当人类接着种下了这些收获来的产生突变的种子后，农民又一次可以从这些种子的后代中得到所有产生突变的种子，收获它们，播种它们，而后代中未产生突变的那些种子就落到地上，而无法得到了。这样，农民就180度地改变了自然选择的方向：原来成功的基因突然变得具有毁灭性了，而毁灭性的突变却变得成功了。1万多年前，这种对不脱落的小麦和大麦麦秆的无意识的选择，显然是人类对植物的第一个重大的“改良”。这个变化标志着新月沃地农业的开始。

The second type of change was even less visible to ancient hikers. For annual plants growing in an area with a very unpredictable climate, it could be lethal if all the seeds sprouted quickly and simultaneously. Were that to happen, the seedlings might all be killed by a single drought or frost, leaving no seeds to propagate the species. Hence many annual plants have evolved to hedge their bets by means of germination inhibitors, which make seeds initially dormant and spread out their germination over several years. In that way, even if most seedlings are killed by a bout of bad weather, some seeds will be left to germinate later.

第二个改变甚至是古代旅行者更难以觉察的。对于在气候变化无常的地区生长的一年生植物来说，如果所有的种子都迅速地同时发芽，那可能是毁灭性的。如果发生了这种情况，那么只要一次干旱或霜冻就可能把幼苗全都杀死，连传种接代的种子都没有了。因此，许多一年生植物演化的结果是通过发芽抑制剂来减少损失，使种子在开始阶段休眠，然后在几年里分批发芽。这样，即使大多数幼苗由于一次恶劣的天气而死光，剩下的一些种子还会在以后发芽。

A common bet-hedging adaptation by which wild plants achieve that result is to enclose their seeds in a thick coat or armor. The many wild plants with such adaptations include wheat, barley, peas, flax, and sunflowers. While such late-sprouting seeds still have the opportunity to germinate in the wild, consider what must have happened as farming developed. Early farmers would have discovered by trial and error that they could obtain higher yields by tilling and watering the soil and then sowing seeds. When that happened, seeds that immediately sprouted grew into plants whose seeds were harvested and planted in the next year. But many of the wild seeds did not immediately sprout, and they yielded no harvest.

野生植物赖以减少损失的一种普遍的适应性变化，是把它们的种子裹在一层厚厚的皮壳或保护层中。产生这种适应性变化的这许多植物包括小麦、大麦、亚麻或向日葵。虽然这些后发芽的种子仍然有机会在野外发芽，但请考虑一下随着农业的发展而必然发生的情况。早期的农民可能在反复试验中发现，他们可以通过松土、浇水然后播种的办法来获得更高的产量。如果是这样，种子就会立即发芽并长成植物，它们的种子又可以收获下来在来年种下。但许多野生植物的种子不会立即发芽，因此种下去也不会有任何收成。

Occasional mutant individuals among wild plants lacked thick seed coats or other inhibitors of germination. All such mutants promptly sprouted and yielded harvested mutant seeds. Early farmers wouldn't have noticed the difference, in the way that they did notice and selectively harvest big berries. But the cycle of sow / grow / harvest / sow would have selected immediately and unconsciously for the mutants. Like the changes in seed dispersal, these changes in germination inhibition characterize wheat, barley, peas, and many other crops compared with their wild ancestors.

野生植物中偶然产生突变的个体没有厚厚的种皮，也没有其他的发芽抑制剂。所有这些突变体迅速发芽，最后产生了突变的种子。早期的农民可能没有注意到这种差异，他们只知道去注意和有选择地收获大的浆果。但播种—生长—收获—播种这种循环会立即无意识地选择了那些突变体。和种子传播方面的变化一样，发芽抑制方面的这些变化是小麦、大麦、豌豆以及其他许多作物的共同特点，而这是它们的野生祖先所没有的。

The remaining major type of change invisible to early farmers involved plant reproduction. A general problem in crop development is that occasional mutant plant individuals are more useful to humans ^{(for example, because of bigger or less bitter seeds)} than are normal individuals. If those desirable mutants proceeded to interbreed with normal plants, the mutation would immediately be diluted or lost. Under what circumstances would it remain preserved for early farmers?

早期农民觉察不到的另一个重要变化与植物的繁殖直接有关。植物培育的一个普遍问题是：偶然产生突变的植物个体比正常的个体更有益于人类^{(例如，由于种子较大和苦味较少)}。如果这些可取的突变体接下去同正常的植物进行品种间的杂交，这种突变就会立刻被淡化或完全失去。那么，对早期农民来说，在什么情况下这种突变会继续保留下来？

For plants that reproduce themselves, the mutant would automatically be preserved. That's true of plants that reproduce vegetatively ^{(from a tuber or root of the parent plant)}, or that are hermaphrodites capable of fertilizing themselves. But the vast majority of wild plants don't reproduce that way. They're either hermaphrodites incapable of fertilizing themselves and forced to interbreed with other hermaphrodite individuals ^{(my male part fertilizes your female part, your male part fertilizes my female part)}, or else they occur as separate male and female individuals, like all normal mammals. The former plants are termed self-incompatible hermaphrodites; the latter, dioecious species. Both were bad news for ancient farmers, who would thereby have promptly lost any favorable mutants without understanding why.

对自我繁殖的植物来说，突变体会自动地保留下来。对无性繁殖^{(用亲代植物的块茎或根来繁殖)}的植物或能够自花受精的雌雄同株的植物来说，情况也是如此。但大多数野生植物都不是用这种方法来繁殖的。它们或者是雌雄同株，但不能自花受精，必须同其他雌雄同株的个体进行品种间的杂交^{(我的雄蕊使你的雌蕊受精，你的雄蕊使我的雌蕊受精)}，或者像所有正常的哺乳动物一样，是雌雄异体。前一种植物叫做自交不亲和雌雄同株，后一种植物叫做雌雄异株。这两种情况对古代农民来说都不是好消息，因为他们可能因此而糊里糊涂地失去所有对他们有利的突变体。

The solution involved another type of invisible change. Numerous plant mutations affect the reproductive system itself. Some mutant individuals developed fruit without even having to be pollinated, resulting in our seedless bananas, grapes, oranges, and pineapples. Some mutant hermaphrodites lost their self-incompatibility and became able to fertilize themselves—a process exemplified by many fruit trees such as plums, peaches, apples, apricots, and cherries. Some mutant grapes that normally would have had separate male and female individuals also became self-fertilizing hermaphrodites. By all these means, ancient farmers, who didn't understand plant reproductive biology, still ended up with useful crops that bred true and were worth replanting, instead of initially promising mutants whose worthless progeny were consigned to oblivion.

解决办法涉及另一种难以觉察的变化。许多植物的突变影响到其自身的繁殖系统。有些产生突变的个体甚至不需要授粉就可以结出果实来，其结果就使我们有了无籽的香蕉、葡萄、柑橘和菠萝。有些产生突变的雌雄同株植物失去了它们的自交不亲和性，而变得能够自花受精——许多果树，如李、桃、苹果、杏和樱桃就是这一过程的例证。有些产生突变的葡萄通常都是雌雄异体，但也会变成自花受精的雌雄同株。古代的农民虽然还不懂得植物繁殖生物学，但仍然用所有这些办法最后得到了一些有用的作物，这些作物能够繁殖纯种，因而值得去重新种植，而不是那些本来被看好的突变体，它们的后代则因为毫无价值而湮没无闻。

Thus, farmers selected from among individual plants on the basis not only of perceptible qualities like size and taste, but also of invisible features like seed dispersal mechanisms, germination inhibition, and reproductive biology. As a result, different plants became selected for quite different or even opposite features. Some plants ^{(like sunflowers)} were selected for much bigger seeds, while others ^{(like bananas)} were selected for tiny or even nonexistent seeds. Lettuce was selected for luxuriant leaves at the expense of seeds or fruit; wheat and sunflowers, for seeds at the expense of leaves; and squash, for fruit at the expense of leaves. Especially instructive are cases in which a single wild plant species was variously selected for different purposes and thereby gave rise to quite different-looking crops. Beets, grown already in Babylonian times for their leaves ^{(like the modern beet varieties called chards)}, were then developed for their edible roots and finally ^{(in the 18th century)} for their sugar content ^{(sugar beets)}. Ancestral cabbage plants, possibly grown originally for their oily seeds, underwent even greater diversification as they became variously selected for leaves ^{(modern cabbage and kale)}, stems ^(kohlrabi), buds ^{(brussels sprouts)}, or flower shoots ^{(cauliflower and broccoli)}.

因此，农民就是从一些特有的植物中进行选择，他们选择所根据的标准，不但有大小和味道这些看得见的品质，而且还有诸如种子传播机制、发芽抑制和繁殖生物学这些看不见的特点。结果，不同的植物由于十分不同的或甚至相反的特点而得到选择。有些植物^{(如向日葵)}由于大得多的种子而得到选择，而另一些植物^(如香蕉)则由于种子小或没有种子而得到选择。选择生菜则取其茂盛的叶子而舍其种子或果实；选择小麦和向日葵则取其种子而舍其叶；选择南瓜则取其果实而舍其叶。特别有意思的是，由于不同的目的，对于一种野生植物可以有不同的选择，从而产生了外观十分不同的作物。甜菜在巴比伦时代即已有种植，不过那时种植甜菜是为了它们的叶^{(如叫做牛皮菜的现代甜菜品种)}，后来再种植则是为了它们可吃的根，最后^{(在18世纪)}则是为了它们所含的糖份^{(糖用甜菜)}。最早的卷心菜可能原本是为了它们的含油种子而被种植的，后来经过甚至更大的分化，对它们也就有了不同的选择：有的选择了叶^{(现代的卷心菜和羽衣甘蓝)}，有的选择了茎^(撇蓝)，有的选择了芽^{(抱子甘蓝)}，有的选择了花芽^{(花椰菜和花茎甘蓝)}。

So far, we have been discussing transformations of wild plants into crops as a result of selection by farmers, consciously or unconsciously. That is, farmers initially selected seeds of certain wild plant individuals to bring into their gardens and then chose certain progeny seeds each year to grow in the next year's garden. But much of the transformation was also effected as a result of plants' selecting themselves. Darwin's phrase “natural selection” refers to certain individuals of a species surviving better, and / or reproducing more successfully, than competing individuals of the same species under natural conditions. In effect, the natural processes of differential survival and reproduction do the selecting. If the conditions change, different types of individuals may now survive or reproduce better and become “naturally selected,” with the result that the population undergoes evolutionary change. A classic example is the development of industrial melanism in British moths: darker moth individuals became relatively commoner than paler individuals as the environment became dirtier during the 19th century, because dark moths resting on a dark, dirty tree were more likely than contrasting pale moths to escape the attention of predators.

迄今为止，我们已经讨论了野生植物由于农民有意无意的选择而变成了作物的问题。就是说，农民开始时选择了某些植物个体的种子，带回来种在自家的园子里，然后每年都挑选一些后代的种子，再在下一年种在园子里。但这种变化的很大一部分也由于植物的自我选择而受到了影响。达尔文所说的“自然选择”指的是一个物种的某些个体在自然条件下比同一物种中与之竞争的个体可以生存得更好与^(或)繁殖得更成功。实际上，是差别生存状况和繁殖状况的自然过程作出了这种选择。如果条件改变了，不同种类的个体有可能生存或繁殖得更好，从而“被自然所选择”，其结果就是这个种群经历了演化改变。一个典型的例子是英国飞蛾工业黑化现象的发展：在19世纪，随着环境变得更脏，颜色深的飞蛾比颜色浅的飞蛾更为普通，因为栖息在深暗肮脏的树上的深色飞蛾，相形之下比浅色飞蛾更有可能逃脱捕食者的注意。

Much as the Industrial Revolution changed the environment for moths, farming changed the environment for plants. A tilled, fertilized, watered, weeded garden provides growing conditions very different from those on a dry, unfertilized hillside. Many changes of plants under domestication resulted from such changes in conditions and hence in the favored types of individuals. For example, when a farmer sows seeds densely in a garden, there is intense competition among the seeds. Big seeds that can take advantage of the good conditions to grow quickly will now be favored over small seeds that were previously favored on dry, unfertilized hillsides where seeds were sparser and competition less intense. Such increased competition among plants themselves made a major contribution to larger seed size and to many other changes developing during the transformation of wild plants into ancient crops.

与工业革命改变了飞蛾的环境几乎一样，农业耕作也改变了植物的环境。经过松土、施肥、浇水和除草的园地所提供的生长环境，完全不同于山坡上干燥、未施肥的园地。植物在驯化中所产生的许多变化都来自此类条件的变化，因此也就有了那些处于有利条件的植物品种的变化。例如，如果农民在园子里播下的种子密密麻麻，那么在种子之间就会产生剧烈的竞争。大的种子可以利用良好的条件迅速生长，此时它们所处的地位就比小的种子有利，因为小的种子先前是长在干燥、未施肥的山坡上的，而那里种子比较稀少，竞争也不那么激剧，所以只有生长在那样的地方才对它们有利。植物本身之间这种持续的竞争，对于获得较大的种子和野生植物变成古代作物期间逐步形成的其他许多变化，起到了重要的促进作用。

WHAT ACCOUNTS FOR the great differences among plants in ease of domestication, such that some species were domesticated long ago and others not until the Middle Ages, whereas still other wild plants have proved immune to all our activities? We can deduce many of the answers by examining the well-established sequence in which various crops developed in Southwest Asia's Fertile Crescent.

就植物的驯化来说，有些植物在很久以前就驯化了，有些直到中世纪才驯化，而还有一些野生植物竟然不受我们所有活动的影响。这方面的巨大差异的原因是什么？我们可以考察一下不同作物在西南亚新月沃地发展的固定顺序来推断出许多答案。

It turns out that the earliest Fertile Crescent crops, such as the wheat and barley and peas domesticated around 10,000 years ago, arose from wild ancestors offering many advantages. They were already edible and gave high yields in the wild. They were easily grown, merely by being sown or planted. They grew quickly and could be harvested within a few months of sowing, a big advantage for incipient farmers still on the borderline between nomadic hunters and settled villagers. They could be readily stored, unlike many later crops such as strawberries and lettuce. They were mostly self-pollinating: that is, the crop varieties could pollinate themselves and pass on their own desirable genes unchanged, instead of having to hybridize with other varieties less useful to humans. Finally, their wild ancestors required very little genetic change to be converted into crops—for instance, in wheat, just the mutations for nonshattering stalks and uniform quick germination.

事情原来是这样的：新月沃地最早的作物，如小麦、大麦和豌豆，大约是在1万年前驯化的，它们都起源于呈现许多优势的野生祖先。它们已经可以食用，而且在野生状态下产量很高。它们很容易生长，只要播种或栽植就行了。它们生长迅速，播种后不消几个月就可收获了。对于仍然处于流浪的猎人和定居的村民之间的早期农民来说，这是一个巨大的优点。它们很容易贮藏，这和后来的许多作物如草莓和生菜不同。它们大都是自花传粉：就是说，各种作物都是自己给自己传授花粉，把它们自己的合意的基因毫无改变地传递下去，而不必同其他的对人类不大有用的品种进行杂交。最后，为了转化为作物，它们的野生祖先很少需要在基因方面产生什么变化——例如，就小麦来说，只要产生使麦粒不脱落和迅速而均匀的发芽的突变就行了。

A next stage of crop development included the first fruit and nut trees, domesticated around 4000 B.C. They comprised olives, figs, dates, pomegranates, and grapes. Compared with cereals and legumes, they had the drawback of not starting to yield food until at least three years after planting, and not reaching full production until after as much as a decade. Thus, growing these crops was possible only for people already fully committed to the settled village life. However, these early fruit and nut trees were still the easiest such crops to cultivate. Unlike later tree domesticates, they could be grown directly by being planted as cuttings or even seeds. Cuttings have the advantage that, once ancient farmers had found or developed a productive tree, they could be sure that all its descendants would remain identical to it.

作物培育的下一阶段包括在公元前4000年左右驯化的最早的果树和坚果树，其中有橄榄树、无花果树、枣树、石榴树和葡萄藤。同谷物和豆科植物相比，它们的缺点是种植后至少要3年才开始结实，而达到盛产期则要等到10年之后。因此，只有那些已完全过上了定居的乡村生活的人，才有可能种植这些作物。然而，这些早期的果树和坚果树仍然是最容易栽种的作物。和后来驯化的树木不同，它们可以用插枝甚或播种的办法来直接栽种。插枝还有一个好处：一旦古代农民发现或培育了一棵多产的果树，他们可以确信，这棵树的所有后代可以长得和它一模一样。

A third stage involved fruit trees that proved much harder to cultivate, including apples, pears, plums, and cherries. These trees cannot be grown from cuttings. It's also a waste of effort to grow them from seed, since the offspring even of an outstanding individual tree of those species are highly variable and mostly yield worthless fruit. Instead, those trees must be grown by the difficult technique of grafting, developed in China long after the beginnings of agriculture. Not only is grafting hard work even once you know the principle, but the principle itself could have been discovered only through conscious experimentation. The invention of grafting was hardly just a matter of some nomad relieving herself at a latrine and returning later to be pleasantly surprised by the resulting crop of fine fruit.

第三阶段涉及一些栽培起来难得多的果树，包括苹果、梨、李和樱桃。这些树不能靠插枝来种植。用种子来种也是白费力气，因为即使是其中优秀品种的后代也十分易变，所结的果实也多半没有价值。这些树要靠困难的嫁接技术来种植，而这个技术在中国农业开始后很久才发展起来。即使你懂得嫁接的原理，嫁接也仍然是一项困难的工作。不仅如此，这原理本身也只有通过有意识的实验才能发现。发明嫁接这种事情，大概不再是什么一个流浪者在某个排泄处方便，后来在返回时惊喜地发现那里竟因此而长出了结有甘甜水果的树来。

Many of these late-stage fruit trees posed a further problem in that their wild progenitors were the opposite of self-pollinating. They had to be cross-pollinated by another plant belonging to a genetically different variety of their species. Hence early farmers either had to find mutant trees not requiring cross-pollination, or had consciously to plant genetically different varieties or else male and female individuals nearby in the same orchard. All those problems delayed the domestication of apples, pears, plums, and cherries until around classical times. At about the same time, though, another group of late domesticates arose with much less effort, as wild plants that established themselves initially as weeds in fields of intentionally cultivated crops. Crops starting out as weeds included rye and oats, turnips and radishes, beets and leeks, and lettuce.

许多在晚近阶段发展起来的果树提出了另外一个问题，因为它们的野生祖先完全不是自花传粉。它们必须由属于同一品种但产生遗传变异的另一植物进行异花传粉。因此，早期的农民要么必须去找到不需要异花传粉的果树，要么必须有意识地去种植不同的遗传品种或同一果园中附近的雄性和雌性个体。所有这些问题把苹果、梨、李和樱桃的驯化时间一直推迟到古典时期前后。然而，大约与此同时，还有一批在晚近出现的驯化植物却得来全不费工夫，它们本来都是长在有意栽培的作物地里的杂草之类的野生植物。原本是杂草的作物包括黑麦、燕麦、芜菁、萝卜、甜菜、韭葱和生菜。

ALTHOUGH THE DETAILED sequence that I've just described applies to the Fertile Crescent, partly similar sequences also appeared elsewhere in the world. In particular, the Fertile Crescent's wheat and barley exemplify the class of crops termed cereals or grains ^{(members of the grass family)}, while Fertile Crescent peas and lentils exemplify pulses ^{(members of the legume family, which includes beans)}. Cereal crops have the virtues of being fast growing, high in carbohydrates, and yielding up to a ton of edible food per hectare cultivated. As a result, cereals today account for over half of all calories consumed by humans and include five of the modern world's 12 leading crops ^{(wheat, corn, rice, barley, and sorghum)}. Many cereal crops are low in protein, but that deficit is made up by pulses, which are often 25 percent protein ^{(38 percent in the case of soybeans)}. Cereals and pulses together thus provide many of the ingredients of a balanced diet.

虽然我刚才详细介绍的一系列作物适用于新月沃地，但部分类似的一系列作物也出现在世界其他地方。尤其是，新月沃地的小麦和大麦是被称之为谷物^{(属禾本科)}的那类作物的代表，而新月沃地的豌豆和兵豆则是豆类^{(属豆科，包括大豆)}的代表。谷类作物的优点是生长快，碳水化合物含量高，每公顷耕地可产1吨食物。因此，今天的谷物占人类消耗的全部卡路里的半数以上，并包括现代世界上12种主要作物中的5种^{(小麦、玉米、稻米、大麦和高粱)}。许多谷类作物蛋白质含量低，但这一缺陷可以由豆类来弥补，因为豆类的蛋白质通常达25%^{(大豆为38%)}。因此，谷物和豆类一起为均衡饮食提供了许多必不可少的成分。

As Table 7.1 ^{(next page)} summarizes, the domestication of local cereal / pulse combinations launched food production in many areas. The most familiar examples are the combination of wheat and barley with peas and lentils in the Fertile Crescent, the combination of corn with several bean species in Mesoamerica, and the combination of rice and millets with soybeans and other beans in China. Less well known are Africa's combination of sorghum, African rice, and pearl millet with cowpeas and groundnuts, and the Andes' combination of the noncereal grain quinoa with several bean species.

正如表7.1扼要说明的那样，当地谷物和豆类组合的驯化，标志着许多地区粮食生产的开始。最为人熟知的例子，是新月沃地的小麦和大麦与豌豆和兵豆的组合，中美洲的玉米与几种豆类的组合，以及中国的稻米和小米与大豆和其他豆类的组合。不大为人所知的是非洲高粱、非洲稻米和珍珠稗与豇豆和野豆的组合，以及安第斯山脉的非谷类的昆诺阿藜与几种豆类的组合。

Table 7.1 also shows that the Fertile Crescent's early domestication of flax for fiber was paralleled elsewhere. Hemp, four cotton species, yucca, and agave variously furnished fiber for rope and woven clothing in China, Mesoamerica, India, Ethiopia, sub-Saharan Africa, and South America, supplemented in several of those areas by wool from domestic animals. Of the centers of early food production, only the eastern United States and New Guinea remained without a fiber crop.

表7.1同时表明，为获得纤维在新月沃地曾对亚麻进行过早期驯化，在其他地方也有类似情况。大麻、4种棉花、丝兰和龙舌兰在不同时期为中国、中美洲、印度、埃塞俄比亚、非洲撒哈拉沙漠以南地区和南美洲提供了制绳和织布的纤维，在这些地区的几个地方，还用驯化动物的绒毛作为补充。在早期粮食生产的这些中心中，只有美国东部和新几内亚仍然没有纤维作物。

The table gives major crops, of five crop classes, from early agricultural sites in various parts of the world. Square brackets enclose names of crops first domesticated elsewhere; names not enclosed in brackets refer to local domesticates. Omitted are crops that arrived or became important only later, such as bananas in Africa, corn and beans in the eastern United States, and sweet potato in New Guinea. Cottons are four species of the genus Gossypium, each species being native to a particular part of the world; squashes are five species of the genus Cucurbita. Note that cereals, pulses, and fiber crops launched agriculture in most areas, but that root and tuber crops and melons were of early importance in only some areas.

该表列出了世界各地早期农业地点的五种主要作物。方括号内是首次在其他地方种植的作物名称；未括在括号内的名称指当地家养动物。省略了抵达或后来才变得重要的作物，如非洲的香蕉、美国东部的玉米和豆类以及新几内亚的红薯。棉花是棉属的四个物种，每个物种都原产于世界的特定地区；南瓜属有五种。请注意，谷物、豆类和纤维作物在大多数地区推动了农业的发展，但块根和块茎作物以及甜瓜仅在一些地区具有早期重要性。

Alongside these parallels, there were also some major differences in food production systems around the world. One is that agriculture in much of the Old World came to involve broadcast seeding and monoculture fields, and eventually plowing. That is, seeds were sown by being thrown in handfuls, resulting in a whole field devoted to a single crop. Once cows, horses, and other large mammals were domesticated, they were hitched to plows, and fields were tilled by animal power. In the New World, however, no animal was ever domesticated that could be hitched to a plow. Instead, fields were always tilled by hand-held sticks or hoes, and seeds were planted individually by hand and not scattered as whole handfuls. Most New World fields thus came to be mixed gardens of many crops planted together, rather than monoculture.

同这些类似之处相比，全世界的粮食生产体系中也存在着某些重大的差异。其中的一个差异是：在世界上的许多地方，农业开始涉及种子撒播和农田单作以及最后用牲畜犁地等问题。就是说，用手把种子一把把撒下去，从而使整块田因而只种一种作物。一旦牛、马和其他大型哺乳动物得到驯化，它们就被套上了犁，于是农田就由畜力来耕作。然而，在新大陆还没有驯化过任何可以套上犁头的动物。相反，在那里耕地始终是用手持的棍棒或锄头，而种子也是用手一颗颗种下去，而不是满把的撒播。因此，新大陆的大部分园地都是许多作物混种在一起，而不是单作。

Another major difference among agricultural systems involved the main sources of calories and carbohydrates. As we have seen, these were cereals in many areas. In other areas, though, that role of cereals was taken over or shared by roots and tubers, which were of negligible importance in the ancient Fertile Crescent and China. Manioc ^{(alias cassava)} and sweet potato became staples in tropical South America, potato and oca in the Andes, African yams in Africa, and Indo-Pacific yams and taro in Southeast Asia and New Guinea. Tree crops, notably bananas and breadfruit, also furnished carbohydrate-rich staples in Southeast Asia and New Guinea.

农业体系中的另一个重大差异涉及卡路里和碳水化合物的主要来源问题。我们已经看到，在许多地区，这方面的主要来源是谷物。不过，在另一些地区，谷物的这一任务被根和块茎接管了或分担了，虽然根和块茎在古代的新月沃地和中国是无关紧要的。在赤道南美洲主食是木薯和甘薯，在安第斯山脉是马铃薯和圆齿酢浆草的块茎，在非洲是非洲薯蓣，在东南亚和新几内亚是印度洋-太平洋地区的薯蓣和芋艿。树生作物主要的有香蕉和面包果，它们也是东南亚和新几内亚的富含碳水化合物的主食。

THUS, BY ROMAN times, almost all of today's leading crops were being cultivated somewhere in the world. Just as we shall see for domestic animals too ^{(Chapter 9)}, ancient hunter-gatherers were intimately familiar with local wild plants, and ancient farmers evidently discovered and domesticated almost all of those worth domesticating. Of course, medieval monks did begin to cultivate strawberries and raspberries, and modern plant breeders are still improving ancient crops and have added new minor crops, notably some berries ^{(like blueberries, cranberries, and kiwifruit)} and nuts ^{(macadamias, pecans, and cashews)}. But these few modern additions have remained of modest importance compared with ancient staples like wheat, corn, and rice.

因此，到了罗马时代，今天的几乎所有作物都已在世界上的某个地方得到驯化。正如我们还将在家畜方面看到的那样^(第九章)，古代的狩猎采集族群非常熟悉当地的野生植物，而古代的农民显然也已发现并驯化了几乎所有值得驯化的动物。当然，中古的僧侣确已开始栽培草莓和树莓，而现代的培育植物的人仍在改良古代的作物，并已增加了一些新的次要作物，主要是一些浆果^{(如乌饭树的蓝色浆果、越橘和猕猴桃)}和坚果^{(澳洲坚果、美洲山核桃和腰果)}。但和古代的一些主食如小麦、玉米和稻米相比，这些新添的现代作物始终只具有不太大的重要性。

Still, our list of triumphs lacks many wild plants that, despite their value as food, we never succeeded in domesticating. Notable among these failures of ours are oak trees, whose acorns were a staple food of Native Americans in California and the eastern United States as well as a fallback food for European peasants in famine times of crop failure. Acorns are nutritionally valuable, being rich in starch and oil. Like many otherwise edible wild foods, most acorns do contain bitter tannins, but acorn lovers learned to deal with tannins in the same way that they dealt with bitter chemicals in almonds and other wild plants: either by grinding and leaching the acorns to remove the tannins, or by harvesting acorns from the occasional mutant individual oak tree low in tannins.

不过，在我们所列举的关于驯化成功的例子中仍然缺乏许多野生植物。尽管它们具有食用价值，但我们却不曾成功地驯化它们。在我们驯化失败的这些例子中，引人注目的是橡树。橡实不但是欧洲农民在荒年作物歉收时的应急食物，而且也是加利福尼亚和美国东部的印第安人的主食。橡实具有营养价值，含有丰富的淀粉和油。和许多在其他方面可以食用的野生食物一样，大多数橡实含有味苦的丹宁酸，但爱吃橡实的人学会了用处理杏仁和其他野生植物中味苦的化学物质的同样办法来处理丹宁酸：或者用研磨和过滤来去掉丹宁酸，或者只从丹宁酸含量低的偶然产生突变的橡树上收获橡实。

Why have we failed to domesticate such a prized food source as acorns? Why did we take so long to domesticate strawberries and raspberries? What is it about those plants that kept their domestication beyond the reach of ancient farmers capable of mastering such difficult techniques as grafting?

为什么我们不能驯化像橡实这样宝贵的粮食来源呢？为什么我们花了那么长的时间去驯化草莓和树莓？对那些植物的驯化，即使是掌握了像嫁接这样困难的技术的古代农民也会束手无策，这又是怎么一回事呢？

It turns out that oak trees have three strikes against them. First, their slow growth would exhaust the patience of most farmers. Sown wheat yields a crop within a few months; a planted almond grows into a nut-bearing tree in three or four years; but a planted acorn may not become productive for a decade or more. Second, oak trees evolved to make nuts of a size and taste suitable for squirrels, which we've all seen burying, digging up, and eating acorns. Oaks grow from the occasional acorn that a squirrel forgets to dig up. With billions of squirrels each spreading hundreds of acorns every year to virtually any spot suitable for oak trees to grow, we humans didn't stand a chance of selecting oaks for the acorns that we wanted. Those same problems of slow growth and fast squirrels probably also explain why beech and hickory trees, heavily exploited as wild trees for their nuts by Europeans and Native Americans, respectively, were also not domesticated.

事情原来是这样的：橡树有3个不利因素。首先，它们生长缓慢，可能使大多数农民失去耐心。小麦种下去不消几个月就可得到收成；杏仁种下去3、4年后就可长成能够结果实的树；但种下一颗橡实可能在10年或更长的时间里不会有什么收益。其次，橡树所结的坚果无论是大小还是味道都适于松鼠，而我们都见到过松鼠埋藏、挖掘和吃橡实的情景。如果偶尔有一颗橡实松鼠忘记把它挖出，那么这颗橡实就可长出橡树来。有数以10亿计的松鼠，每一只松鼠每一年把数以百计的橡实传播到几乎任何一个适于橡树生长的地方。这样，我们人类就不可能为我们所需要的橡实去选择橡树。橡树生长缓慢和松鼠行动迅速这些问题大概也说明了为什么山毛榉和山核桃树同样未能驯化的原因，虽然欧洲人和美洲土著分别对这两种树种大量地加以利用以获得它们的坚果。

Finally, perhaps the most important difference between almonds and acorns is that bitterness is controlled by a single dominant gene in almonds but appears to be controlled by many genes in oaks. If ancient farmers planted almonds or acorns from the occasional nonbitter mutant tree, the laws of genetics dictate that half of the nuts from the resulting tree growing up would also be nonbitter in the case of almonds, but almost all would still be bitter in the case of oaks. That alone would kill the enthusiasm of any would-be acorn farmer who had defeated the squirrels and remained patient.

最后，杏仁和橡实的最重要差异也许是：杏仁的苦味由单一的优势基因所控制，而橡实的苦味似乎由许多基因所控制。如果古代农民栽种了偶然产生不苦的突变的杏仁或橡实，那么根据遗传规律，如果是巴旦杏树，结果，长成的树上的杏仁有一半可能也是不苦的，而如果是橡树，则几乎所有橡实可能仍然是苦的。仅仅这一点就足以使任何想要种橡实的农民的热情荡然无存，尽管他们已经赶走了松鼠并且保持耐心。

As for strawberries and raspberries, we had similar trouble competing with thrushes and other berry-loving birds. Yes, the Romans did tend wild strawberries in their gardens. But with billions of European thrushes defecating wild strawberry seeds in every possible place ^{(including Roman gardens)}, strawberries remained the little berries that thrushes wanted, not the big berries that humans wanted. Only with the recent development of protective nets and greenhouses were we finally able to defeat the thrushes, and to redesign strawberries and raspberries according to our own standards.

至于草莓和树莓，我们在与鸫和其他喜吃浆果的鸟儿的竞争中遇到了同样的困难。是的，罗马人的确在他们的园子里照料过野草莓。但是，由于千百万只欧洲鸫把野草莓的种子排泄在每一个可能的地方^{(包括罗马人的园子里)}，所以草莓始终是鸫想要吃的小浆果，而不是人想要吃的大浆果。由于近来保护网和温室的发展，我们才终于能够把鸫打败，并根据我们自己的标准来重新设计草莓和树莓。

WE'VE THUS SEEN that the difference between gigantic supermarket strawberries and tiny wild ones is just one example of the various features distinguishing cultivated plants from their wild ancestors. Those differences arose initially from natural variation among the wild plants themselves. Some of it, such as the variation in berry size or in nut bitterness, would have been readily noticed by ancient farmers. Other variation, such as that in seed dispersal mechanisms or seed dormancy, would have gone unrecognized by humans before the rise of modern botany. But whether or not the selection of wild edible plants by ancient hikers relied on conscious or unconscious criteria, the resulting evolution of wild plants into crops was at first an unconscious process. It followed inevitably from our selecting among wild plant individuals, and from competition among plant individuals in gardens favoring individuals different from those favored in the wild.

因此，我们已经看到，超市上的大草莓和野生的小草莓之间的差异只是一个例子，用来说明把人工培育的植物与其野生祖先区别开来的许多特征。这些差异首先来自野生植物本身之间的自然变异。有些变异，如浆果的大小和坚果的苦味方面的变异，可能很快就被古代的农民注意到了。其他变异，如种子传播机制或种子休眠方面的变异，在现代植物学兴起之前，可能并未被人类认出来。但是，不管古代旅行者对可食用的野生植物的选择是否依赖于自觉的或不自觉的选择标准，由此而产生的野生植物向作物的演化起先总是一种无意识的过程。这是我们对野生植物个体进行选择的必然结果，是园子里各植物个体之间竞争的结果，而这种竞争所偏爱的个体和在野外得天独厚的个体是不同的。

That's why Darwin, in his great book On the Origin of Species, didn't start with an account of natural selection. His first chapter is instead a lengthy account of how our domesticated plants and animals arose through artificial selection by humans. Rather than discussing the Galápagos Island birds that we usually associate with him, Darwin began by discussing—how farmers develop varieties of gooseberries! He wrote, “I have seen great surprise expressed in horticultural works at the wonderful skill of gardeners, in having produced such splendid results from such poor materials; but the art has been simple, and as far as the final result is concerned, has been followed almost unconsciously. It has consisted in always cultivating the best-known variety, sowing its seeds, and, when a slightly better variety chanced to appear, selecting it, and so onwards.” Those principles of crop development by artificial selection still serve as our most understandable model of the origin of species by natural selection.

这就是为什么达尔文在他的伟大著作《物种起源》中并不是一开始就解释自然选择问题的原因。他的第一章反而详细说明了我们的驯化动植物是如何通过人类的人为选择而出现的。达尔文不是讨论我们通常认为和他联系在一起的加拉帕戈斯群岛^[2]上的鸟类，而是一上来就讨论——农民是怎样培育出不同品种的醋栗的！他写道，“我已经看到园艺学著作中对园丁们在用这样差的材料取得这样了不起的成果方面的令人叹为观止的技术所表现出来的巨大的惊奇；但这种技术是简单的，就其最后结果来说，对这一技术的采用也几乎是无意识的。它在于总是去培育最出名的品种，播下它的种子，然后当碰巧出现了一个稍好一点的品种时，再去选择它，就这样地进行下去。”通过人为选择来培育作物的这些原则仍然可以成为我们的关于物种起源通过自然选择的最可理解的模式。

注释：

¹. 图坦卡蒙：古埃及第十八王朝国王，英国埃及学家H·卡特于1922年发现其陵墓，发掘时见其墓室完好，内有金棺、法老木乃伊和大量珍贵文物。——译者

². 加拉帕戈斯群岛，在厄瓜多尔西部，即科隆岛。——译者