Chapter 21 Epilogue: The Future of Human History as a Science
Yali's question gets to the heart of the human condition and is at the crux of post-Pleistocene human history.Now that we have completed this short tour of the continents, how shall we answer Yali?
I would say this to Yali: The marked differences between the long-term histories of the peoples of the continents are due not to inherent differences in the peoples themselves, but to differences in their environments.I suspect that if the Aboriginal population of Australia and the Aboriginal population of Eurasia could be swapped in the late Pleistocene, then the original Aboriginal Australians may now occupy not only Eurasia, but also most of the Americas and Australia, Whereas the original Eurasian aborigines may now be reduced to some ravaged scattered populations of Australia.For this kind of statement, you may dismiss it as meaningless at first, because this experiment is imagined, and the result I am talking about is impossible to prove.But historians can use the method of backtesting to evaluate related hypotheses.For example, we can examine what would happen if European farmers were moved to Greenland or the Great Plains of the United States, or if farmers originally from China moved to the Chatham Islands, the rainforests of Borneo, the volcanic lands of Java or Hawaii .These experiments proved that these peoples with a common ancestor either died out, or returned to hunter-gatherer groups, or went on to establish complex states depending on the environment.Similarly, if Aboriginal Australian hunter-gatherers were moved to Flinders Island, Tasmania, or southern Australia, they would either end up extinct, or become hunter-gatherers with the simplest technology in the modern world, or become Those who build ditches and intensively manage productive fishing grounds.
There are, of course, countless differences in the environments of the continents, and it is these differences that have shaped the trajectory of human societies.Listing every possible difference isn't enough to answer Yali's question, though.In my opinion, only 4 sets of differences are the most important.
The first set of differences are continent-to-continent differences in the species of wild plants and animals that can be used as starting species for domestication.This is because food production is decisive both in its ability to accumulate a surplus to feed specialized human resources not engaged in food production, and in its ability to form a population so large that even before any technological and political advantage has developed , Just relying on the number of people can have a military advantage.For these two reasons, all stages of development from small, immature chiefdoms to economically complex, socially stratified, and politically centralized societies were based on food production.
But most wild species of plants and animals proved unsuitable for domestication: food production has been based on a relatively small number of livestock and crops.It turns out that continents vary widely in the amount of wildlife available for domestication because of differences in size and in the extinction of large mammals during the late Pleistocene.The extinction of large mammals was far more severe in Australia and the Americas than in Eurasia or Africa.Therefore, in terms of biological species, Eurasia is the most endowed, Africa is next, America is next, and Australia is the least, as in the case of Yeli's New Guinea (New Guinea is 70% of Eurasia. one-third, and its original large mammals became extinct in the late Pleistocene).
On each continent, the domestication of plants and animals was concentrated in a few particularly favorable centers covering only a small fraction of the total area of the continent.As far as technological innovations and political institutions are concerned, most societies receive far more from other societies than they can invent themselves.The spread and migration within a continent thus played an important role in the development of its societies, which in the long run, by processes revealed in such simple form by the Maori musketeers, were ( where circumstances permit) to share each other's development results.That is, societies that originally lacked a certain advantage either received it from societies that had it, or (failed to do so) were replaced by these other societies.
So the second set of factors are those that affect the rate of spread and migration, which varies greatly from continent to continent.It is fastest in Eurasia due to its east-west axis and its relatively small ecological and geographical barriers.The principle is the simplest for the dispersal of crops and livestock, since this dispersal depends greatly on climate and therefore on latitude.The same holds true for technological inventions, if they can be exploited to their fullest potential without making changes to the particular environment.The rate of spread is slower in Africa and especially in the Americas due to the north-south main axis and geographical and ecological barriers of the two continents.This spread was also difficult in traditional New Guinea, where the rugged terrain and long main lines of high mountains prevented any significant progress in political and linguistic unification.
Related to these factors affecting intracontinental dispersal is a third set of factors affecting intercontinental dispersal that may also have contributed to the accumulation of a local collection of domesticated plants and animals and technologies.The ease of transmission varies from continent to continent because some continents are more isolated than others.In the past 6000 years, the easiest transmission was from Eurasia to sub-Saharan Africa, and most of Africa's livestock was acquired through this transmission.But the spread between the eastern and western hemispheres made no contribution to the complex societies of the Americas, which were separated from Eurasia at low latitudes by a wide ocean, and at high latitudes were separated by terrain and hunter-gatherer habitats. The climate is far from Eurasia.To primitive Australia, separated from Eurasia by a series of water barriers in the Indonesian archipelago, the only attested contribution of Eurasia to it was the dingo.
The fourth and final set of factors is the differences between continents in terms of size and total population.A larger area or population means more potential inventors, more competing societies, more innovations to adopt—and greater pressure to adopt and retain them, because Any society that fails to do so will tend to be eliminated by its competitors.This fate met the Pygmies of Africa and many other hunter-gatherers who were displaced by farmers.The opposite example is the stubborn and conservative ancient Norse farmers in Greenland, who also met the fate of being replaced by Eskimo hunter-gatherers, because in Greenland's conditions, these Eskimos' survival methods and survival techniques were better than these ancient Norsemen. much superior.Of the world's land masses, Eurasia has the largest area and the greatest number of competing societies, with Australia and New Guinea far behind, and Tasmania not far behind.The total area of the Americas, while large, is geographically and ecologically fragmented, effectively like several smaller continents not closely connected.
These 4 groups of factors constitute large differences in circumstances that can be objectively quantified and not disputed.My subjective impression is that New Guineans are generally smarter than Eurasians, and while people can dispute this, they cannot deny that New Guinea is much smaller than Eurasia, and New Guinea has a larger animal species than Eurasia. Subcontinents are much less.But mentioning these environmental differences inevitably leads historians to label them inflamed as "geographic determinism."This label seems to have unpleasant connotations, since it amounts to saying that human creativity is worthless, or that we humans are just passive robots helplessly programmed by climate, fauna, and flora.Of course, such doubts are unfounded.Without human ingenuity, we might all still be cutting meat and drinking blood with stone tools today, just as our ancestors did a million years ago.All human societies contain inventive individuals.It just so happens that some environments offer more starting species and more favorable conditions for exploiting inventions than others.
The answers seemed lengthier and more complicated than what Yali himself might have wanted to get.Historians, however, may think these answers are too short and too simple.Compressing the 13,000-year history of each continent into a book of more than 400 pages is equivalent to sharing one page for each continent about every 150 years. In this way, succinctness and simplification are inevitable.However, this compression also has a compensating benefit: long-term comparisons of regions yield insights that are not possible from short-term studies of single societies.
Of course, the series of controversies raised by Yali's question remain unresolved.At present, we can only propose some incomplete answers and matters for future research, rather than a fully developed theory.What needs to be worked on now is to develop human history as a science alongside the accepted historical sciences of astronomy, geology, and evolutionary biology.It seems appropriate, therefore, to conclude the book with a look at the future of the discipline of history and to conclude with some unresolved questions in general terms.
We have proposed four sets of factors that seem to be the most important to account for the differences between continents.The most immediate extension of this book, therefore, would be to further quantify these differences, thereby more convincingly demonstrating their role.To account for differences in starting species used for domestication, I have provided figures for the total number of large wild terrestrial mammalian herbivores per continent (Table 9.2) and large-grained cereals (Table 8.1) .A possible extension of this book would be to collect corresponding numbers of large-grained legumes (legumes) such as beans, peas, and vetches.Also, I mentioned some of the factors that disqualify large mammals from domestication candidates, but I did not tabulate how many of these candidates per continent were disqualified for each such factor.It is interesting to do so, especially for Africa, where the percentage of disqualified animals for domestication is higher than in Eurasia: among the factors that make some animals disqualified for domestication , which factors were most important in Africa, and what selections determined why African mammals so frequently lost their candidacy for domestication?Some quantifiable data should also be collected to verify my preliminary calculations showing different propagation velocities along the main axes of Eurasia, America, and Africa.
A second extension of the book will involve a smaller geographic and shorter time frame than the ones already covered in this book.For example, the following obvious question may have occurred to the reader: within Eurasia, why were European societies, those colonizing the Americas and Australia, and not Fertile Crescent societies or China and India? societies, technologically advanced, and politically and economically dominant in the modern world?If a historian had lived at any time from 85d00 BC to 1450 AD, if he was trying to predict the future trajectory of history, he would definitely think that the eventual dominance of Europe was the most unlikely outcome , because Europe was the most backward of the three regions of the Old World for most of the past 10,000 years.From 8500 BC until after 500 AD, Greece first and then Italy rose up. During this period, almost all the major inventions in western Eurasia—animal domestication, plant domestication, literature, metallurgy, wheels, countries, etc. etc. - all appear in or near the Fertile Crescent.Europe west or north of the Alps made no meaningful contribution to Old World technology or civilization until the watermill spread profusely after about 900 CE, it was just a Where the fruits of development are received.Even from AD 1000 to 1450, science and technology came to Europe overwhelmingly from Islamic societies between India and North Africa, not the other way around.In just those centuries, China was technologically ahead of the world and started food production almost as early as the Fertile Crescent.
So, why did the Fertile Crescent and China finally cede their huge lead of thousands of years to Europe, which started late?Of course, one can point to some immediate factors that contributed to the rise of Europe: its merchant class, capitalism and the gradual formation of patent protection for inventions, its failure to produce despotic monarchs and overwhelming taxation, and its The Greco-Judeo-Christian tradition of critical empiricist inquiry.Still, for all these proximate causes, one must ask the question of the ultimate cause: Why did these proximate causes appear in Europe and not in China or the Fertile Crescent?
In the case of the Fertile Crescent, the answer is clear.The Fertile Crescent had the head start due to its local concentration of domesticable flora and fauna.Once it loses that advantage, it no longer has any compelling geographic advantages to speak of.The disappearance of this lead in the westward movement of some powerful empires can be charted in detail.After the rise of some countries in the Fertile Crescent in the fourth millennium BC, the center of power remained in the Fertile Crescent at first, with the Babylonian, Hittite, Assyrian, and Persian empires taking turns.Power finally shifted irretrievably westward for the first time, as the Greeks under Alexander the Great failed to conquer all advanced societies from Greece eastward to India in the 4th century BC.With Rome's conquest of Greece in the 2nd century BC, power moved further west, and after the fall of the Roman Empire, power finally shifted to western and northern Europe.
Just compare the modern Fertile Crescent with the ancients' descriptions of it, and the main factors driving the westward movement of power become immediately apparent.Today, the terms "Fertile Crescent" and "world leader in food production" are ludicrous.Vast areas of what was once the Fertile Crescent are now deserts, semi-deserts, steppes, and heavily eroded or saline lands unsuitable for agriculture.The ephemeral wealth of certain countries in the region based on a single non-renewable source of oil masks the region's chronic poverty and inability to feed itself.
In ancient times, however, much of the Fertile Crescent and the Eastern Mediterranean, including Greece, was covered with forests.The transformation of this region from fertile woodland to eroded scrubland or desert has been described by paleobotanists and archaeologists.Its woodlands were cleared for agriculture, felled for building lumber, spared for firewood, or burned for plaster.Primary productivity (proportional to rainfall) is low due to low rainfall, so vegetation regeneration cannot keep pace with destruction, especially when there are large numbers of goats overgrazing.With the absence of trees and turf, soil erosion occurred, valleys silted up, and irrigated agriculture in low-rainfall environments led to a build-up of salt in the soil.These processes began in the Neolithic Age and have continued into modern times.For example, the last forests near Petra, the ancient Nabataean capital of Jordan in present-day Jordan, were cleared by the Ottoman Turks when they built the railway before World War I.
Thus, Fertile Crescent and Eastern Mediterranean societies unfortunately arose in an ecologically fragile environment.They destroy their own resource base, tantamount to ecological suicide.Beginning with the oldest societies in the East (Fertile Crescent), each Eastern Mediterranean society in turn undercut itself, and in the process, power moved westward.The northern and western parts of Europe did not suffer the same fate, not because their inhabitants were wiser, but because they happened to live in a favorable environment with abundant rainfall and rapid vegetation regeneration.After 7,000 years of food production, large areas of northern and western Europe can still sustain highly productive, intensive agriculture today.In fact, Europe got its crops, livestock, technology, and writing system from the Fertile Crescent, which in turn lost itself as a major center of power and invention.
This is how the Fertile Crescent lost its huge early lead over Europe.Why did China also lose this lead?China's backwardness is at first surprising because of China's undoubted advantages: food production seems to have appeared as early as in the Fertile Crescent; ecological diversity, resulting in a diverse array of crops, animals, and technologies; a vast area and abundance of products that feed the largest population in the world in this region; and an environment that is not as arid or ecologically fragile as the Fertile Crescent, making China was able to maintain highly productive and intensive agriculture nearly 10,000 years later, although its environmental problems were growing and more severe than in western Europe.
These favorable conditions and leading advantages made medieval China a technological leader in the world.China's long list of significant technological firsts includes cast iron, the compass, gunpowder, paper, printing, and many other inventions mentioned earlier.It also once led the world in political power, navigation and sea control. At the beginning of the 15th century, it sent across the Indian Ocean, as far as the east coast of Africa, each fleet consisted of several hundred ships up to 400 feet long and a total of 2,800 people.These voyages also predate Columbus's three humble boats across the narrow Atlantic Ocean to the east coast of America by several decades.Fasco da Gama led his three humble boats to sail eastward around the Cape of Good Hope in Africa, and Europe began to colonize East Asia.Why didn't Chinese ships sail west around the Cape of Good Hope and colonize Europe before Gamma?Why didn't Chinese ships cross the Pacific to colonize the west coast of America?In short, why is China ceding its technological lead to Europe, which was so far behind?
The fate of China's Western Fleet gives us a clue.From 1405 to 1433 AD, these fleets sailed from China seven times.Later, due to a partial political change that can occur anywhere in the world, the fleet's voyage was suspended: a power struggle broke out between two factions at the Chinese court (the eunuchs and those who opposed them).The former faction supported the dispatch and command of fleets on long voyages.Therefore, when the latter faction gained the upper hand in the power struggle, it stopped sending fleets, and finally dismantled the docks and banned ocean shipping.This event reminds us of legislation that killed public electric lighting in London in the 1880s, isolationism in the United States between the First and Second World Wars and many retrograde measures in many countries, all due to localized political disputes .But in China, the situation is different because the whole region is politically unified.One decision made the whole of China stop the voyage of the fleet.That momentary decision turned out to be irreversible, for there was no longer any shipyard to build ships to justify the folly of that momentary decision, nor any shipyard to serve as a center for rebuilding new ones.
Now contrast these events in China with what happened when some expeditionary fleets began their voyages from politically divided Europe.Christopher Columbus was born in Italy and then switched to the service of the Duke of Anjou in France and then King of Portugal.Columbus had asked the king to send a ship to let him sail west to explore.His request was rejected by the king, so he appealed to the Duke of Medina-Sedonia, who was also rejected, then he appealed to the Count of Medina-Seli, but was still refused, and finally he appealed to the Duke of Medina-Sedonia. As for the king and queen of Spain, they refused his first request, but finally granted him when he asked again.Had Europe been united under any of these first three rulers, its colonization of America might have failed from the start.
In fact, it was precisely because Europe was divided that Columbus succeeded for the fifth time in persuading one of the hundreds of princes and nobles to sponsor his voyage.Once Spain started the European colonization of the Americas in this way, other European countries saw the wealth flowing into Spain, and immediately 6 more European countries joined the ranks of colonizing the Americas.The same is true of European cannon, electric lighting, printing, small firearms, and countless other inventions: each invention is at first either neglected or opposed by the habits of the people in some parts of Europe, but once a certain region adopts it, it always eventually spreads to the rest of Europe.
These outcomes of Europe's division stand in stark contrast to those of China's unification.In addition to making the decision to stop overseas voyages, China's court also made decisions to stop other activities: abandoning the development of an ingenious water-powered spinning machine, stepped back from the brink of an industrial revolution in the 14th century, After leading the world in mechanical clocks, it was demolished or almost completely destroyed, and mechanical devices and general technology were not developed after the late 15th century.These potentially harmful effects of unification have revived in modern China, especially the frenzy of the "Cultural Revolution" of the 1960s and 1970s, when decisions by one or a few leaders shut down the nation's school system5 years long.
The constant unification of China and the permanent division of Europe have a long history.The most fertile regions of modern China were first politically unified in 221 BC and have remained so for most of the time since.China has had only one writing system since its inception, one dominant language for a long time, and a solid cultural unity for 2,000 years.In contrast, Europe has always been far from unity: in the 14th century it was still divided into 1,000 independent small states, in 1500 AD there were 500 small states, in the 1980s it was reduced to a minimum of 25 states, and Now, as I write this sentence, it has risen to nearly 40 countries.There are still 45 languages in Europe, each with its own modified alphabet, and the cultural differences are even greater.Europe's deep-seated obsession with division continues today as divisions within Europe continue to frustrate even modest attempts at European unity through the EEC.
So to understand the real problem of China's ceding political and technological preeminence to Europe is to understand the problem of China's long-term unification and Europe's long-term division.The answer is again represented by a map (see figure below).The coastline of Europe is jagged, and it has 5 major peninsulas, each of which is like an island suspended in the sea. On all these peninsulas, independent languages, races and governments have been formed; Greece, Italy, Iberia, Denmark and Norway /Sweden.China's coastline is much flatter, and only the nearby Korean peninsula has gained importance as a separate island.There are two islands in Europe (Great Britain and Ireland), both of which are large enough to maintain their political independence and maintain their own language and ethnic characteristics. One of the islands (Great Britain) has a large area, It is close to the European continent, so it has become an important independent European power.But even China's two largest islands, Taiwan and Hainan, are less than half the size of Ireland, neither of which is a significant independent polity; and Japan's geographical isolation places it in the modern It had previously been politically isolated from the Asian continent to a far greater degree than Great Britain was politically isolated from the European continent.Europe is divided into separate linguistic, ethnic and political units by some high mountains (Alps, Pyrenees, Carpathians and Norwegian border mountains), while China's mountains east of the Tibetan plateau are not so insurmountable obstacles.The center of China is connected from east to west by two navigable river systems (the Yangtze and Yellow Rivers) in fertile alluvial valleys, and from south to north by the relatively convenient connection between these two major river systems (finally connected by canals). Vehicle and ship combined transport into one.As a result, China was early and decisively influenced by two large productive core regions, which were only insignificantly separated from each other, and then competed and merged into a single center.Europe's two largest rivers, the Rhine and the Danube, are smaller and flow through far fewer places in Europe.Unlike China, Europe has many scattered small core regions, none large enough to have long-term decisive influence on other core regions, each of which has been the center of some independent countries in history.
Once China was finally unified in 221 B.C., no other independent state could possibly have arisen and long existed in China.Although there were periods of schism after 221 BC, there was always a reunification in the end.But the unification of Europe was beyond the power of determined conquerors such as Napoleon, Napoleon, and Hitler; even the Roman Empire at its height did not control more than half of Europe.
Thus, geographical accessibility and very general internal barriers gave China an initial advantage.The different crops, livestock, technologies, and cultural identities of North China, South China, the coastal areas, and the interior contributed to the eventual unification of China.For example, millet cultivation, bronze technology, and writing appeared in North China, while rice cultivation and cast iron technology appeared in South China.I devote a large part of this book to the problem of the diffusion of technology in the absence of insurmountable barriers.But China's geographic reach turned out to be a disadvantage, and a single decision by an autocrat could, and has done so more than once, thwart reforms and innovations.By contrast, the geographical fragmentation of Europe created dozens or hundreds of independent, competing small states and centers of invention.If one country does not pursue a certain reform and innovation, another country will do so, forcing its neighbors to do the same or be conquered or left behind economically.Europe's geographic barriers were enough to prevent political unity, but not enough to stop the spread of technology and ideas.Never before in Europe has an absolute monarch been able to cut off the creative source of the whole of Europe as in China.
These comparisons suggest that geographic accessibility can have both positive and negative effects on technological development.Therefore, in the long run, technology is likely to develop fastest in regions where geographical convenience is not too high and not too low, but moderate.The technological developments of China, Europe, and possibly the Indian subcontinent over the past 1,000 years are examples of the practical effects of high, medium, and low levels of geographic convenience.
Of course, there are other factors that also contributed to the different historical processes in different regions of the Eurasian defense.For example, the Fertile Crescent, China, and Europe have long been threatened, but to varying degrees, by barbaric invasions by horse-riding nomads of the steppes of Central Asia.One of these nomads (the Mongols) finally destroyed the ancient irrigation systems of Iran and Iraq, but none of the Asian nomads managed to gain a foothold in the forests of western Europe beyond the Hungarian plains.Environmental factors also include: the Fertile Crescent's intervening geographical location, which controls the trade routes linking China and India to Europe, and China's distance from other advanced civilizations in Eurasia, making China effectively a A huge isolated island within a continent.China's relative isolation is particularly relevant to its practice of adopting technology and then rejecting it, reminiscent of the exclusion of Tasmania and other islands (chapters 13 and 15). chapter).However, this brief discussion can at least show that environmental factors are related not only to the broadest patterns of history, but also to smaller-scale and shorter-period historical patterns.
The history of the Fertile Crescent and China also holds a salutary lesson for the modern world: Circumstances change, and being first in the past does not guarantee that you will be first in the future.One might even wonder whether the geographical inferences employed throughout this book have finally become irrelevant in the modern world, where ideas can be instantly disseminated on the Internet and goods can routinely be airlifted from continent to continent in one go. another continent.It appears that some entirely new rules have been imposed on competition among the nations of the world, and as a result new powers like Korea, Malaysia, and especially Japan have emerged.
However, when we think about it carefully, we find that these so-called new rules are just a modified version of the old rules.Yes, the transistor invented by Bell Laboratories in the eastern United States in 1947 leaped 8,000 miles to Japan to start the electronics industry—but it didn't make the leap any closer to Zaire or Paraguay to start new industries.The countries that leapt into the emerging powers are still those that were absorbed thousands of years ago into the old supremacy centers of power based on food production, or were recolonized by peoples from those centers .Unlike Zaire or Paraguay, Japan and other emerging powers were quick to exploit transistors because their subjects already had a long history of writing, metal machinery, and centralized government.The world's two earliest centers of food production, the Fertile Crescent and China, still dominate the modern world, either through their descendant states (modern China) or by being located in Countries in the immediate vicinity (Japan, Korea, Malaysia, and Europe), or those that were recolonized or ruled by their diaspora (US, Australia, Brazil).Prospects for world domination by sub-Saharan Africans, Aboriginal Australians and American Indians still look bleak.The hand of the historical process in 8000 BC still holds us tightly.
Among other factors related to answering Yali's question, cultural factors and the influence of individual ethnic groups appear to be more prominent.Let me talk about cultural factors first.The characteristics of human cultures vary widely around the world.Some cultural differences are undoubtedly the product of environmental differences, and I have discussed many examples of this in this book.But there is an important issue concerning the possible significance of local cultural factors that are not related to the environment.A minor cultural factor may emerge for local, momentary and insignificant reasons, but once it has arisen it becomes invariable, making it easier for society to accept some of the more important cultural choices, like applying chaos theory to As other scientific fields have shown.This cultural process belongs to the unknown factors of history, and it is these factors that tend to make history unpredictable.
As an example, I mentioned the standard typewriter keyboard problem in Chapter 13.Among the many competing keyboard designs, this standard keyboard stood out and began to be adopted for trivial and specific reasons, such as the technology of typewriter manufacturing in the United States in the early 1860s, the promotion of typewriters, and a Cincinnati's creation of the School of Sketching and Typing, a decision by a lady named Longley in 1882, and the triumph of Frank McGlynn, Mrs. Longley's distinguished typist student, for a much publicized Completely defeated Ms. Longley's non-standard-keyed typewriter competitor, Louis Taub, in the typing competition.That decision could have helped another typewriter keyboard to be invented at any one of innumerable stages from the 1860s to the 1880s; competitors.Once the decision was made, however, the Standard Typewriter keyboard gained such a firm status that it was adopted in computer keyboard design a century later.Specific reasons, equally insignificant, now untraceable due to age, may have been the reasons why the Sumerians adopted the base 12 system instead of the base 10 system (the base 12 system that gave rise to our modern的60分钟一小时、24小时一天、12个月一年和圆周360度），而中美洲普遍使用的运算系统则是20进制（产生了它的使用两个并行周期的历法，一个周期有20天，每天都有一个名称，一个周期是一年有365天）。
关于打字机、时钟和历法设计的这些细节并没有妨碍采用它们的社会在竞争中取得成功。但我们很容易想象出它们可能会产生的妨碍。例如，如果美国的打字机标准键盘都没有被世界上其他地方所采用——臂如说，如果日本或欧洲采用了效率高很多的德伏夏克键盘——那么，这个在19世纪作出的微不足道的决定，对于20世纪美国技术的竞争地位可能产生巨大的影响。
同样，对中国儿童的研究表明，如果教会他们用字母给汉语语音标音（称为拼音），他们就能比学习有几千个符号的传统的中国文字更快地学会写字。有人说，传统的中国文字的出现是因为它们便于区别大量的意义不同但发育相同的汉语词（同音异义词）。果真如此，那么汉语中丰富的同音异义词可能对中国社会中识字的作用产生了巨大的影响，但如认为中国环境中存在某种因素促使选择了一种同音异义词丰富的语言，似乎也未必如此。复杂的安第斯山文明没有能发明出文字，这是否可以用某种语言因素或文化因素来予以解释？否则就令人难以理解了。印度的环境中是否存在某种因素，使它容易接受涉及社会经济地位的种姓制度，而不顾对印度技术发展所造成的严重后果？中国的环境中是否存在某种因素，使它容易接受可能也对历史产生深期影响的儒家哲学和文化保守主义？为什么普度众生的宗教（基督教和伊斯兰教）在欧洲人和西亚人中而不是在中国人中成为殖民和征服的动力？
这些例子说明了涉及文化特质的范围广泛的问题。这些文化特质与环境无关，而且在开始时也几乎没有什么重要的意义，但它们可能逐步形成有影响的历久不衰的文化特点。它们的重要意义在于提出了一个重要的没有得到回答的问题。解决这个问题的最佳途径，就是集中注意力于那些在考虑了主要环境因素影响之后仍然令人费解的历史模式。
具有特质的个人的影响又是怎样的况？一个为人们所熟悉的例子是1944年6月20日行刺希特勒的图谋和同时在柏林举行起义的计划功败垂成。这两件事都是德国人策划的，们深信不可能打赢战争，于是就在德俄两国军队的东部战线仍然主要在俄国境内时，他们希望寻求和乎。希特勒被放在会议桌下的公文包里的一颗定时炸弹炸伤；如果公文包放得稍稍靠近希特勒的坐椅，他也许就被炸死了。如果希特勒真的被炸死，如果第二次世界大战在当时结束了，那么现代的东欧地图和冷战进程可能就大为改观了。
不大为人所知但甚至更加重大的事件是1930年夏天的一次交通事故。那是希特勒在德国夺权之前两年多发生的事。当时他坐在一辆轿车的“死亡座”上（前徘右边的乘客座位上），他的车和一辆满载的有挂车的卡车相撞。幸亏卡车及时刹车，才没有碾过希特勒的座车把它压死。鉴于希特勒的精神机能障碍在决定纳粹的政策与成功方面所达到的程度，如果那个卡车司机晚一秒钟刹车，即使万一发生了第二次世界大战，情况大概也会十分不同。
我们还可以想出其他一些个人，他们的特质和希特勒的特质一样显然对历史产生了影响，他们是：亚历山大大帝、、、基督、列宁、马丁·路德、印加帝国皇帝帕查库蒂、、·和祖鲁国王沙卡，就举这么几个。他们中的每一个人究竟在多大程度上真正改变了事件的进程，而不“只”是恰巧最合适的人在最合适的时间出现在最合适的地点？
一个极端是历史学家的观点：“世界的历史就是人（原文如此）在这个世界上所取得的成就的历史，实际上就是在这个世界上活动的伟人的历史。”另一个极端是普鲁士政治家奥托·冯·俾斯麦的观点，他与卡莱尔不同，他对政治的内幕活动具有长期的直接经验，他说：“政治家的任务就是倾听上帝在历史上走过的脚步声，并且当他在身旁经过时努力抓住他的上衣的后下摆，跟他一起前进。”
同文化的特质一祥，个人的特质也是历史进程中的未知因素。无论是从环境的力量来看，还是事实上从任何可以归纳起来的原因来看，个人的特质都会使历史变得无法说明。然而，就本书的论题来说，所谓个人的特质几乎是毫不相干的，因为即使是伟人理论的最热情的支持者也觉得难以用几个伟人来解释历史最广泛的模式。也许，亚历山大大帝的确轻轻推动了一下欧亚大陆西部已经有了文字、粮食生产和铁器的国家的历史进程；但他与这样的事实毫无关系：当澳大利亚还仍然维持着没有文字、没有金属工具的特猎采集部落时，欧亚大陆西部已经有了有文字的、从事粮食生产和使用铁器的国家了。不过，具有某些特质的个人的历史的影响究竟有多广泛和多持久，这仍然是一个可以讨论的问题。
历史这门学科一般认为不是一门科学，而是比较接近人文学科。历史最多可以划归社会科学，而在社会科学中，它又被列为最少科学性的一种。虽然研究政治的专业常常被称为“政治学”，而诺贝尔经济学奖也指称“经济学”，但历史系即使有也很少称自己为“历史学系”。大多数历史学家并不把自己看作科学家，也很少在一些公认的科学领域及其方法论方面受过训练。在许多警句中部有历史不过是一大堆细节这种认识：“历史不过是一个又一个讨厌的事实”，“历史或多或少都是骗人的鬼话”，“历史和万花筒一样毫无规律可言”，等等。
无可否认，从研究历史中去获得普遍原则，要比从研究行星轨道中去获得普遍原则来得困难。然而，在我看来，这些困难并不是决定性的。其他一些历史学科，包括天文学、气候学、生态学、演化生物学、地质学和古生物学，虽然也碰到了同样的困难，但它们在自然科学中的地位却是牢固的。不幸的是，人们对历史的概念常常是以物理学和其他几个运用同样方法的领域为基础的。这些领域的科学家往往由于无知面对某些领域不屑一顾，因为对这些领域这些方法是不适用的，因此必须寻找其他方法——例如我自己的研究领域生态学和演化生物学就是如此。不过，诸记住：“science”（科学）这个词的意思是“knoeledge”（知识）（来自拉丁语的scire即“to know”［知道］和scientia即“knowledge”［知识］），而知识是要通过任何对特定领域最合适的方法来获得的。因此，我对研究人类历史的人所面临的困难非常同情。
广义的历史科学（包括天文学之类的学科）具有许多共同的特点，把它们同非历史科学如物理学、化学和分子生物学之类区别开来。我可以跳出4个方面的差别来讨论：方法、因果关系、预测和复杂程度。
在物理学中，获得知识的主要方法是实验室实验，人们通过实验来处理结果有疑问的参数，用被认为恒定的参数来进行平行的对照实验，保留始终恒定的参数，复制对实验的处理和对照试验，并获得定量数据。这种方法在化学和分子生物学中也是十分有用的，它在许多人的思想里成了科学本身，因此实验常常被认为是科学方法的本质。但在许多历史科学中，实验室实验显然只能起很小的作用，或者完全不起作用。人不能阻碍银河系的形成，不能发动和制造飓风和冰河期，不能用实验的方法使几个国家公园里的灰熊灭绝，也不能再现恐龙的演化过程。人只能用别的方法获得这些历史科学方面的知识，如观察、比较和所谓的自然实验（这一点我回头再来讨论）。
历史科学研究的是一连串的直接原因和终极原因。在大部分物理学和化学中，“终极原因”、“目的”和“功能”这些概念是没有意义的，但它们对于了解一般的生命系统尤其是人类的活动，是至关重要的。例如，北极兔的毛色在夏天是棕色，到冬天就变为白色，但研究北极兔的演化生物学家并不满足于弄清楚从毛色色素的分子结构和生物合成途径的角度来研究的毛色的普通直接原因。更重要的问题是功能（逃避捕食者的保护色？）和终极原因（从没有季节性毛色变化的组代兔群开始的自然选择？）。同样，一个欧洲历史学家不会满足于把描写为经过代价巨大的泛欧战争之后刚刚获得了和平。了解形成对比的一连串导致的事件，对于了解为什么1918年后而不是1815年后的几十年内又一次爆发了代价甚至更大的泛欧战争是必不可少的。但化学家并不为两个气体分子的碰撞规定某种目的或功能，他们也不会去寻找这种碰撞的终极原因。
历史科学和非历史科学之间的另一个差异就是预测。在化学和物理学中，测验一个人是否了解某个系统就是看他能否成功地预测这个系统的未来变化。另外，物理学家还往往看不起演化生物学和历史，因为这两个领城似乎通不过这种测验。在历史科学中，人们可以提供一种事后的解释（例如，为什么6600万年前一颖小行星对地球的撞击会使得恐龙灭绝，而没有使其他许多物种灭绝），而事前的预测就比较困难了（如果我们没有过去的实际情况作为指引，我们可能会无法确定哪些物种可能会招致灭绝）。然而，对于未来什么样的资料发现会告诉我们过去所发生的事，历史学家和历史科学家的确作出了井检验了一些预测。
历史系统的性质使预测的企图变得复杂了。对于这些性质，可以用几种不同的方法来加以描写。我们可以指出的是，人类社会和恐龙都是极其复杂的，它们的特点是具有大量的互相反馈的独立变数。结果，较低组织层次上的小小变化可能会引起较高层次上的突变。典型的例子就是1930年险些让希待勒送命的交通事故中，那个卡车司机的刹车反应对第二次世界大战中死伤的1亿人的生命的影响。虽然大多数生物学家都同意生物系统归根到底完全决定于它们的物理性质并服从量子力学的定律，但这些系统的复杂程度实际上意味着这种决定论的因果关系并不能转化为可预测性。量子力学的知识并不能帮助人理解为什么引进的有胎盘食肉动物消灭了那么多的澳大利亚有袋目动物，或者为什么获得第一次世界大战胜利的是协约国而不是同盟国。
每一条冰川，每一团星云，每一次飓风，每一个人类社会，每一个生物物种，甚至每一个个人和某个有性生殖物种的每一个细胞，都是独一无二的，因为它受到那么多的变数的影响，而且是由那么多的可变部分构成的。相比之下，对于物理学家的任何基本粒子和同位素以及化学家的任何分子来说，实际存在物的所有个体彼此都是完全相同的。因此，物理学家和化学家能够在宏观的层次上系统地阐述带有普遍性的决定论的规律，但生物学家和历史学家只能系统地阐述统计学上的趋势。我能以很高的正确概率预测，在我工作的加利福尼亚大学医学中心出生的下1000个婴儿中，男婴的数目不会少于480个，也不会多于520个。但我没有办法事先知道我自己的两个孩子会是男孩。同样，一些历史学家指出，如果当地的人口够多，密度也够大，如果存在发展剩余粮食生产的潜力，那么部落社会也许比不存在上述情况时更有可能发展成为酋长管辖地。但是，每一个这样的当地人口都有其自身的独一无二的特点，其结果是酋长管辖地在墨西哥、危地马拉、秘鲁和马达加斯加的高原地区出现了，但却没有在新几内亚或的高原地区出现。
历史系统尽管有其终极的确定性，但其复杂性和不可预测性是不待言的。描述这种复杂性和不可预测性的另一个办法就是指出，长长的一连串因果关系可能把最后结果同存在于那一科学领域之外的终极原因分开。例如，一颗小行星对地球的撞击可能导致了恐龙的灭绝，但那颗小行星的轨道却是完全由古典力学的定律决定的。但如果有古生物学家生活在6700万年前，他们也不可能预测到恐龙的灭亡迫在眉睫，因为小行星属于一个在其他方面都与恐龙生物学关系疏远的科学领域研究的对象。同样，公元1300年至1500年之间的小冰期也是格陵兰岛上古挪威人灭绝的部分原因，但没有哪个历史学家，也许甚至也没有哪一个现代气候学家能够预到小冰期的到来。
因此，历史学家在确定人类社会史的因果关系时所碰到的困难，大致上类似于天文学家、气候学家、生态学家、演化生物学家、地质学家和古生物学家所碰到的困难。这些领域的每一个领域都在不同程度上受到以下几个方面的因扰：不可能进行可复制的对照实验的介入，大量变数带来的复杂性，每一个系统因而变得独一无二，结果不可能系统地阐述普遍的规律，以及难以预测突现性质和未来变化。历史预测和其他历史科学的预测一样，在大的时空范围内最为适宜，因为这时无数小的时空范围内的独一无二的特点趋于乎衡。正如我的预测下1000个新生婴儿的性别比例但却不能预测我自己两个孩子的性别那样，历史学家能够认识到使美洲和欧亚大陆社会在经过13000年的独立发展后发生碰撞所产生的广泛后果变得不可避免的因素，但却不能认识到1960年美国总统选择的后果。在1960年10月的一次电视辩论会上，四个总统候选人说了些什么之类的细节，可能会使尼克松而不是肯尼迪获得选举的胜利，但却没有谁说了些什么之类的细节，可以阻挡欧洲人征服印第安人。
研究人类史的人怎样才能从其他历史科学的科学家们的经验中获益呢？有一个证明有用的方法就是比较法和所谓的自然实验。虽然无论是研究银河系形成的天文学家还是人类史家，都不可能在有控制的实验室实验中来处理他们的系统，但他们都可以利用自然实验，把一些因存在或不存在（或作用有强有弱的）某种推定的起因而不同的系统加以比较。例如，流行病学家虽然不可以在实验中使人服用大量的盐，但仍然能够通过比较在盐的摄入方面已经存在巨大差异的不同人群，来确定盐的高摄入量的影响；而文化人类学家虽然不能用实验在许多世纪中向不同的人群提供丰富程度不同的资源，但仍然能够通过比较生活在自然资源丰富程度不同的岛屿上的近代波利尼西亚人，来研究资源的丰富程度对人类社会的长期影响。研究人类史的人可以利用多得多的自然实验，而不只是限于比较5个有人居住的大陆。在进行比较时不但可以利用数以百计的较小岛屿上的社会和从每个大陆都能到达的区域性社会，而且也可以利用一些在相当孤立状态中发展了复杂社会的大岛（如日本、马达加斯加、美洲的伊斯帕尼尼奥拉岛、新几内亚、夏威夷和其他许多岛屿）。
任何领域的自然实验，不管是生态领域的还是人类史领域的，生来就容易受到可能的方法论的批评。这些批评不但包括了从观察到的变数之间相互关系来推定因果关系链方面的问题，而且也包括了混淆除关系重大的变数外其他一些变数的自然变异的作用。这些方法论问题已为了某些历史科学而得到了详尽的讨论。特别是流行病学——通过比较不同的人群（通常用历史追溯研究法）来对人类疾病作出论断的科学——长期以来一直成功地运用正式的程序，来处理类似人类社会历史学家所碰到的问题。生态学家也十分注意自然实验问题，因为在许多情况下，用直接的实验介入法来处理相关的生态变量可能是不道德的、不合法的或不可能的，所以生态学家必须把自然实验作为一种方法来使用。演化生物学家近来也发展出一些更复杂的方法，根据对已知的演化史上的不同动植物的比较来作出结论。
总之，我承认，了解人类的历史要比了解某些科学领域的问题困难得多，因为在这些科学领城里，历史是不重要的，起作用的个别变量也比较少。不过，有几个领域已经设计出一些用来分析历史问题的成功的方法。因此，人们普遍承认，对恐龙、星云和冰川的系统阐述属于自然科学领域，而不属于人文学科。但是内省的方法使我们对其他人的行为方式比对恐龙的行为方式产生了多得多的真知灼见。因此，我很乐观，对人类社会的历史研究可以科学地进行，就像对恐龙的研究一样——同时，使我们认识到是什么塑造了现代世界以及是什么可能塑造未来世界，因而使今天我们自己的社会从中获益。
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