These Austronesians, with their Austronesian language and modified Austronesian culture, were already established on Madagascar by the time it was first visited by Europeans, in 1500. This strikes me as the single most astonishing fact of human geography for the entire world. It's as if Columbus, on reaching Cuba, had found it occupied by blue-eyed, blond-haired Scandinavians speaking a language close to Swedish, even though the nearby North American continent was inhabited by Native Americans speaking Amerindian languages. How on earth could prehistoric people of Borneo, presumably voyaging in boats without maps or compa.s.ses, end up in Madagascar?

THE CASE OF Madagascar tells us that peoples' languages, as well as their physical appearance, can yield important clues to their origins. Just by looking at the people of Madagascar, we'd have known that some of them came from tropical Southeast Asia, but we wouldn't have known from which area of tropical Southeast Asia, and we'd never have guessed Borneo. What else can we learn from African languages that we didn't already know from African faces? Madagascar tells us that peoples' languages, as well as their physical appearance, can yield important clues to their origins. Just by looking at the people of Madagascar, we'd have known that some of them came from tropical Southeast Asia, but we wouldn't have known from which area of tropical Southeast Asia, and we'd never have guessed Borneo. What else can we learn from African languages that we didn't already know from African faces?

The mind-boggling complexities of Africa's 1,500 languages were clarified by Stanford University's great linguist Joseph Greenberg, who recognized that all those languages fall into just five families (see Figure 19.2 for their distribution). Readers accustomed to thinking of linguistics as dull and technical may be surprised to learn what fascinating contributions Figure 19.2 makes to our understanding of African history.

If we begin by comparing Figure 19.2 with Figure 19.1, we'll see a rough correspondence between language families and anatomically defined human groups: languages of a given language family tend to be spoken by distinct people. In particular, Afroasiatic speakers mostly prove to be people who would be cla.s.sified as whites or blacks, Nilo-Saharan and Niger-Congo speakers prove to be blacks, Khoisan speakers Khoisan, and Austronesian speakers Indonesian. This suggests that languages have tended to evolve along with the people who speak them.

Concealed at the top of Figure 19.2 is our first surprise, a big shock for Eurocentric believers in the superiority of so-called Western civilization. We're taught that Western civilization originated in the Near East, was brought to brilliant heights in Europe by the Greeks and Romans, and produced three of the world's great religions: Christianity, Judaism, and Islam. Those religions arose among peoples speaking three closely related languages, termed Semitic languages: Aramaic (the language of Christ and the Apostles), Hebrew, and Arabic, respectively. We instinctively a.s.sociate Semitic peoples with the Near East.

However, Greenberg determined that Semitic languages really form only one of six or more branches of a much larger language family, Afroasiatic, all of whose other branches (and other 222 surviving languages) are confined to Africa. Even the Semitic subfamily itself is mainly African, 12 of its 19 surviving languages being confined to Ethiopia. This suggests that Afroasiatic languages arose in Africa, and that only one branch of them spread to the Near East. Hence it may have been Africa that gave birth to the languages spoken by the authors of the Old and New Testaments and the Koran, the moral pillars of Western civilization.

The next surprise in Figure 19.2 is a seeming detail on which I didn't comment when I just told you that distinct peoples tend to have distinct languages. Among Africa's five groups of people-blacks, whites, Pygmies, Khoisan, and Indonesians-only the Pygmies lack any distinct languages: each band of Pygmies speaks the same language as the neighboring group of black farmers. However, if one compares a given language as spoken by Pygmies with the same language as spoken by blacks, the Pygmy version seems to contain some unique words with distinctive sounds.

Originally, of course, people as distinctive as the Pygmies, living in a place as distinctive as the equatorial African rain forest, were surely isolated enough to develop their own language family. However, today those languages are gone, and we already saw from Figure 19.1 that the Pygmies' modern distribution is highly fragmented. Thus, distributional and linguistic clues combine to suggest that the Pygmy homeland was engulfed by invading black farmers, whose languages the remaining Pygmies adopted, leaving only traces of their original languages in some words and sounds. We saw previously that much the same is true of the Malaysian Negritos (Semang) and Philippine Negritos, who adopted Austroasiatic and Austronesian languages, respectively, from the farmers who came to surround them.

The fragmented distribution of Nilo-Saharan languages in Figure 19.2 similarly implies that many speakers of those languages have been engulfed by speakers of Afroasiatic or Niger-Congo languages. But the distribution of Khoisan languages testifies to an even more dramatic engulfing. Those languages are famously unique in the whole world in their use of clicks as consonants. (If you've been puzzled by the name !Kung Bushman, the exclamation mark is not an expression of premature astonishment; it's just how linguists denote a click.) All existing Khoisan languages are confined to southern Africa, with two exceptions. Those exceptions are two very distinctive, click-laden Khoisan languages named Hadza and Sandawe, stranded in Tanzania more than 1,000 miles from the nearest Khoisan languages of southern Africa.

In addition, Xhosa and a few other Niger-Congo languages of southern Africa are full of clicks. Even more unexpectedly, clicks or Khoisan words also appear in two Afroasiatic languages spoken by blacks in Kenya, stranded still farther from present Khoisan peoples than are the Hadza and Sandawe peoples of Tanzania. All this suggests that Khoisan languages and peoples formerly extended far north of their present southern African distribution, until they too, like the Pygmies, were engulfed by the blacks, leaving only linguistic legacies of their former presence. That's a unique contribution of the linguistic evidence, something we could hardly have guessed just from physical studies of living people.

I have saved the most remarkable contribution of linguistics for last. If you look again at Figure 19.2, you'll see that the Niger-Congo language family is distributed all over West Africa and most of subequatorial Africa, apparently giving no clue as to where within that enormous range the family originated. However, Greenberg recognized that all Niger-Congo languages of subequatorial Africa belong to a single language subgroup termed Bantu. That subgroup accounts for nearly half of the 1,032 Niger-Congo languages and for more than half (nearly 200 million) of the Niger-Congo speakers. But all those 500 Bantu languages are so similar to each other that they have been facetiously described as 500 dialects of a single language.

Collectively, the Bantu languages const.i.tute only a single, low-order subfamily of the Niger-Congo language family. Most of the 176 other subfamilies are crammed into West Africa, a small fraction of the entire Niger-Congo range. In particular, the most distinctive Bantu languages, and the non-Bantu Niger-Congo languages most closely related to Bantu languages, are packed into a tiny area of Cameroon and adjacent eastern Nigeria.

Evidently, the Niger-Congo language family arose in West Africa; the Bantu branch of it arose at the east end of that range, in Cameroon and Nigeria; and the Bantu then spread out of that homeland over most of subequatorial Africa. That spread must have begun long ago enough that the ancestral Bantu language had time to split into 500 daughter languages, but nevertheless recently enough that all those daughter languages are still very similar to each other. Since all other Niger-Congo speakers, as well as the Bantu, are blacks, we couldn't have inferred who migrated in which direction just from the evidence of physical anthropology.

To make this type of linguistic reasoning clear, let me give you a familiar example: the geographic origins of the English language. Today, by far the largest number of people whose first language is English live in North America, with others scattered over the globe in Britain, Australia, and other countries. Each of those countries has its own dialects of English. If we knew nothing else about language distributions and history, we might have guessed that the English language arose in North America and was carried overseas to Britain and Australia by colonists.

But all those English dialects form only one low-order subgroup of the Germanic language family. All the other subgroups-the various Scandinavian, German, and Dutch languages-are crammed into northwestern Europe. In particular, Frisian, the other Germanic language most closely related to English, is confined to a tiny coastal area of Holland and western Germany. Hence a linguist would immediately deduce correctly that the English language arose in coastal northwestern Europe and spread around the world from there. In fact, we know from recorded history that English really was carried from there to England by invading Anglo-Saxons in the fifth and sixth centuries A.D. A.D.

Essentially the same line of reasoning tells us that the nearly 200 million Bantu people, now flung over much of the map of Africa, arose from Cameroon and Nigeria. Along with the North African origins of Semites and the origins of Madagascar's Asians, that's another conclusion that we couldn't have reached without linguistic evidence.

We had already deduced, from Khoisan language distributions and the lack of distinct Pygmy languages, that Pygmies and Khoisan peoples had formerly ranged more widely, until they were engulfed by blacks. (I'm using "engulfing" as a neutral all-embracing word, regardless of whether the process involved conquest, expulsion, interbreeding, killing, or epidemics.) We've now seen, from Niger-Congo language distributions, that the blacks who did the engulfing were the Bantu. The physical and linguistic evidence considered so far has let us infer these prehistoric engulfings, but it still hasn't solved their mysteries for us. Only the further evidence that I'll now present can help us answer two more questions: What advantages enabled the Bantu to displace the Pygmies and Khoisan? When did the Bantu reach the former Pygmy and Khoisan homelands?

TO APPROACH THE question about the Bantu's advantages, let's examine the remaining type of evidence from the living present-the evidence derived from domesticated plants and animals. As we saw in previous chapters, that evidence is important because food production led to high population densities, germs, technology, political organization, and other ingredients of power. Peoples who, by accident of their geographic location, inherited or developed food production thereby became able to engulf geographically less endowed people. question about the Bantu's advantages, let's examine the remaining type of evidence from the living present-the evidence derived from domesticated plants and animals. As we saw in previous chapters, that evidence is important because food production led to high population densities, germs, technology, political organization, and other ingredients of power. Peoples who, by accident of their geographic location, inherited or developed food production thereby became able to engulf geographically less endowed people.

When Europeans reached sub-Saharan Africa in the 1400s, Africans were growing five sets of crops (Figure 19.3), each of them laden with significance for African history. The first set was grown only in North Africa, extending to the highlands of Ethiopia. North Africa enjoys a Mediterranean climate, characterized by rainfall concentrated in the winter months. (Southern California also experiences a Mediterranean climate, explaining why my bas.e.m.e.nt and that of millions of other southern Californians often gets flooded in the winter but infallibly dries out in the summer.) The Fertile Crescent, where agriculture arose, enjoys that same Mediterranean pattern of winter rains.

Hence North Africa's original crops all prove to be ones adapted to germinating and growing with winter rains, and known from archaeological evidence to have been first domesticated in the Fertile Crescent beginning around 10,000 years ago. Those Fertile Crescent crops spread into climatically similar adjacent areas of North Africa and laid the foundations for the rise of ancient Egyptian civilization. They include such familiar crops as wheat, barley, peas, beans, and grapes. These are familiar to us precisely because they also spread into climatically similar adjacent areas of Europe, thence to America and Australia, and became some of the staple crops of temperate-zone agriculture around the world.

As one travels south in Africa across the Saharan desert and reencounters rain in the Sahel zone just south of the desert, one notices that Sahel rains fall in the summer rather than in the winter. Even if Fertile Crescent crops adapted to winter rain could somehow have crossed the Sahara, they would have been difficult to grow in the summer-rain Sahel zone. Instead, we find two sets of African crops whose wild ancestors occur just south of the Sahara, and which are adapted to summer rains and less seasonal variation in day length. One set consists of plants whose ancestors are widely distributed from west to east across the Sahel zone and were probably domesticated there. They include, notably, sorghum and pearl millet, which became the staple cereals of much of sub-Saharan Africa. Sorghum proved so valuable that it is now grown in areas with hot, dry climates on all the continents, including in the United States.

The other set consists of plants whose wild ancestors occur in Ethiopia and were probably domesticated there in the highlands. Most are still grown mainly just in Ethiopia and remain unknown to Americans-including Ethiopia's narcotic chat, its banana-like ensete, its oily noog, its finger millet used to brew its national beer, and its tiny-seeded cereal called teff, used to make its national bread. But every reader addicted to coffee can thank ancient Ethiopian farmers for domesticating the coffee plant. It remained confined to Ethiopia until it caught on in Arabia and then around the world, to sustain today the economies of countries as far-flung as Brazil and Papua New Guinea.

The next-to-last set of African crops arose from wild ancestors in the wet climate of West Africa. Some, including African rice, have remained virtually confined there; others, such as African yams, spread throughout other areas of sub-Saharan Africa; and two, the oil palm and kola nut, reached other continents. West Africans were chewing the caffeine-containing nuts of the latter as a narcotic, long before the Coca-Cola Company enticed first Americans and then the world to drink a beverage originally laced with its extracts.

The last batch of African crops is also adapted to wet climates but provides the biggest surprise of Figure 19.3. Bananas, Asian yams, and taro were already widespread in sub-Saharan Africa in the 1400s, and Asian rice was established on the coast of East Africa. But those crops originated in tropical Southeast Asia. Their presence in Africa would astonish us, if the presence of Indonesian people on Madagascar had not already alerted us to Africa's prehistoric Asian connection. Did Austronesians sailing from Borneo land on the East African coast, bestow their crops on grateful African farmers, pick up African fishermen, and sail off into the sunrise to colonize Madagascar, leaving no other Austronesian traces in Africa?

The remaining surprise is that all of Africa's indigenous crops-those of the Sahel, Ethiopia, and West Africa-originated north of the equator. Not a single African crop originated south of it. This already gives us a hint why speakers of Niger-Congo languages, stemming from north of the equator, were able to displace Africa's equatorial Pygmies and subequatorial Khoisan people. The failure of the Khoisan and Pygmies to develop agriculture was due not to any inadequacy of theirs as farmers but merely to the accident that southern Africa's wild plants were mostly unsuitable for domestication. Neither Bantu nor white farmers, heirs to thousands of years of farming experience, were subsequently able to develop southern African native plants into food crops.

Africa's domesticated animal species can be summarized much more quickly than its plants, because there are so few of them. The sole animal that we know for sure was domesticated in Africa, because its wild ancestor is confined there, is a turkeylike bird called the guinea fowl. Wild ancestors of domestic cattle, donkeys, pigs, dogs, and house cats were native to North Africa but also to Southwest Asia, so we can't yet be certain where they were first domesticated, although the earliest dates currently known for domestic donkeys and house cats favor Egypt. Recent evidence suggests that cattle may have been domesticated independently in North Africa, Southwest Asia, and India, and that all three of those stocks have contributed to modern African cattle breeds. Otherwise, all the remainder of Africa's domestic mammals must have been domesticated elsewhere and introduced as domesticates to Africa, because their wild ancestors occur only in Eurasia. Africa's sheep and goats were domesticated in Southwest Asia, its chickens in Southeast Asia, its horses in southern Russia, and its camels probably in Arabia.

The most unexpected feature of this list of African domestic animals is again a negative one. The list includes not a single one of the big wild mammal species for which Africa is famous and which it possesses in such abundance-its zebras and wildebeests, its rhinos and hippos, its giraffes and buffalo. As we'll see, that reality was as fraught with consequences for African history as was the absence of native domestic plants in subequatorial Africa.

This quick tour through Africa's food staples suffices to show that some of them traveled a long way from their points of origin, both inside and outside Africa. In Africa as elsewhere in the world, some peoples were much "luckier" than others, in the suites of domesticable wild plant and animal species that they inherited from their environment. By a.n.a.logy with the engulfing of Aboriginal Australian hunter-gatherers by British colonists fed on wheat and cattle, we have to suspect that some of the "lucky" Africans parlayed their advantage into engulfing their African neighbors. Now, at last, let's turn to the archaeological record to find out who engulfed whom when.

WHAT CAN ARCHAEOLOGY can tell us about actual dates and places for the rise of farming and herding in Africa? Any reader steeped in the history of Western civilization would be forgiven for a.s.suming that African food production began in ancient Egypt's Nile Valley, land of the pharaohs and pyramids. After all, Egypt by 3000 can tell us about actual dates and places for the rise of farming and herding in Africa? Any reader steeped in the history of Western civilization would be forgiven for a.s.suming that African food production began in ancient Egypt's Nile Valley, land of the pharaohs and pyramids. After all, Egypt by 3000 B.C. B.C. was undoubtedly the site of Africa's most complex society, and one of the world's earliest centers of writing. In fact, though, possibly the earliest archaeological evidence for food production in Africa comes instead from the Sahara. was undoubtedly the site of Africa's most complex society, and one of the world's earliest centers of writing. In fact, though, possibly the earliest archaeological evidence for food production in Africa comes instead from the Sahara.

Today, of course, much of the Sahara is so dry that it cannot support even gra.s.s. But between about 9000 and 4000 B.C. B.C. the Sahara was more humid, held numerous lakes, and teemed with game. In that period, Saharans began to tend cattle and make pottery, then to keep sheep and goats, and they may also have been starting to domesticate sorghum and millet. Saharan pastoralism precedes the earliest known date (5200 the Sahara was more humid, held numerous lakes, and teemed with game. In that period, Saharans began to tend cattle and make pottery, then to keep sheep and goats, and they may also have been starting to domesticate sorghum and millet. Saharan pastoralism precedes the earliest known date (5200 B.C. B.C.) for the arrival of food production in Egypt, in the form of a full package of Southwest Asian winter crops and livestock. Food production also arose in West Africa and Ethiopia, and by around 2500 B.C. B.C. cattle herders had already crossed the modern border from Ethiopia into northern Kenya. cattle herders had already crossed the modern border from Ethiopia into northern Kenya.

While those conclusions rest on archaeological evidence, there is also an independent method for dating the arrival of domestic plants and animals: by comparing the words for them in modern languages. Comparisons of terms for plants in southern Nigerian languages of the Niger-Congo family show that the words fall into three groups. First are cases in which the word for a particular crop is very similar in all those southern Nigerian languages. Those crops prove to be ones like West African yams, oil palm, and kola nut-plants that were already believed on botanical and other evidence to be native to West Africa and first domesticated there. Since those are the oldest West African crops, all modern southern Nigerian languages inherited the same original set of words for them.

Next come crops whose names are consistent only among the languages falling within a small subgroup of those southern Nigerian languages. Those crops turn out to be ones believed to be of Indonesian origin, such as bananas and Asian yams. Evidently, those crops reached southern Nigeria only after languages began to break up into subgroups, so each subgroup coined or received different names for the new plants, which the modern languages of only that particular subgroup inherited. Last come crop names that aren't consistent within language groups at all, but instead follow trade routes. These prove to be New World crops like corn and peanuts, which we know were introduced into Africa after the beginnings of transatlantic ship traffic (A.D. 1492) and diffused since then along trade routes, often bearing their Portuguese or other foreign names. 1492) and diffused since then along trade routes, often bearing their Portuguese or other foreign names.

Thus, even if we possessed no botanical or archaeological evidence whatsoever, we would still be able to deduce from the linguistic evidence alone that native West African crops were domesticated first, that Indonesian crops arrived next, and that finally the European introductions came in. The UCLA historian Christopher Ehret has applied this linguistic approach to determining the sequence in which domestic plants and animals became utilized by the people of each African language family. By a method termed glottochronology, based on calculations of how rapidly words tend to change over historical time, comparative linguistics can even yield estimated dates for domestications or crop arrivals.

Putting together direct archaeological evidence of crops with the more indirect linguistic evidence, we deduce that the people who were domesticating sorghum and millet in the Sahara thousands of years ago spoke languages ancestral to modern Nilo-Saharan languages. Similarly, the people who first domesticated wet-country crops of West Africa spoke languages ancestral to the modern Niger-Congo languages. Finally, speakers of ancestral Afroasiatic languages may have been involved in domesticating the crops native to Ethiopia, and they certainly introduced Fertile Crescent crops to North Africa.

Thus, the evidence derived from plant names in modern African languages permits us to glimpse the existence of three languages being spoken in Africa thousands of years ago: ancestral Nilo-Saharan, ancestral Niger-Congo, and ancestral Afroasiatic. In addition, we can glimpse the existence of ancestral Khoisan from other linguistic evidence, though not that of crop names (because ancestral Khoisan people domesticated no crops). Now surely, since Africa harbors 1,500 languages today, it is big enough to have harbored more than four ancestral languages thousands of years ago. But all those other languages must have disappeared-either because the people speaking them survived but lost their original language, like the Pygmies, or because the people themselves disappeared.

The survival of modern Africa's four native language families (that is, the four other than the recently arrived Austronesian language of Madagascar) isn't due to the intrinsic superiority of those languages as vehicles for communication. Instead, it must be attributed to a historical accident: ancestral speakers of Nilo-Saharan, Niger-Congo, and Afroasiatic happened to be living at the right place and time to acquire domestic plants and animals, which let them multiply and either replace other peoples or impose their language. The few modern Khoisan speakers survived mainly because of their isolation in areas of southern Africa unsuitable for Bantu farming.

BEFORE WE TRACE Khoisan survival beyond the Bantu tide, let's see what archaeology tells us about Africa's other great prehistoric population movement-the Austronesian colonization of Madagascar. Archaeologists exploring Madagascar have now proved that Austronesians had arrived at least by Khoisan survival beyond the Bantu tide, let's see what archaeology tells us about Africa's other great prehistoric population movement-the Austronesian colonization of Madagascar. Archaeologists exploring Madagascar have now proved that Austronesians had arrived at least by A.D. A.D. 800, possibly as early as 800, possibly as early as A.D. A.D. 300. There the Austronesians encountered (and proceeded to exterminate) a strange world of living animals as distinctive as if they had come from another planet, because those animals had evolved on Madagascar during its long isolation. They included giant elephant birds, primitive primates called lemurs as big as gorillas, and pygmy hippos. Archaeological excavations of the earliest human settlements on Madagascar yield remains of iron tools, livestock, and crops, so the colonists were not just a small canoeload of fishermen blown off course; they formed a full-fledged expedition. How did that prehistoric 4,000-mile expedition come about? 300. There the Austronesians encountered (and proceeded to exterminate) a strange world of living animals as distinctive as if they had come from another planet, because those animals had evolved on Madagascar during its long isolation. They included giant elephant birds, primitive primates called lemurs as big as gorillas, and pygmy hippos. Archaeological excavations of the earliest human settlements on Madagascar yield remains of iron tools, livestock, and crops, so the colonists were not just a small canoeload of fishermen blown off course; they formed a full-fledged expedition. How did that prehistoric 4,000-mile expedition come about?

One hint is in an ancient book of sailors' directions, the Periplus of the Erythrean Sea Periplus of the Erythrean Sea, written by an anonymous merchant living in Egypt around A.D. A.D. 100. The merchant describes an already thriving sea trade connecting India and Egypt with the coast of East Africa. With the spread of Islam after 100. The merchant describes an already thriving sea trade connecting India and Egypt with the coast of East Africa. With the spread of Islam after A.D. A.D. 800, Indian Ocean trade becomes well doc.u.mented archaeologically by copious quant.i.ties of Mideastern (and occasionally even Chinese!) products such as pottery, gla.s.s, and porcelain in East African coastal settlements. The traders waited for favorable winds to let them cross the Indian Ocean directly between East Africa and India. When the Portuguese navigator Vasco da Gama became the first European to sail around the southern cape of Africa and reached the Kenya coast in 1498, he encountered Swahili trading settlements and picked up a pilot who guided him on that direct route to India. 800, Indian Ocean trade becomes well doc.u.mented archaeologically by copious quant.i.ties of Mideastern (and occasionally even Chinese!) products such as pottery, gla.s.s, and porcelain in East African coastal settlements. The traders waited for favorable winds to let them cross the Indian Ocean directly between East Africa and India. When the Portuguese navigator Vasco da Gama became the first European to sail around the southern cape of Africa and reached the Kenya coast in 1498, he encountered Swahili trading settlements and picked up a pilot who guided him on that direct route to India.

But there was an equally vigorous sea trade from India eastward, between India and Indonesia. Perhaps the Austronesian colonists of Madagascar reached India from Indonesia by that eastern trade route and then fell in with the westward trade route to East Africa, where they joined with Africans and discovered Madagascar. That union of Austronesians and East Africans lives on today in Madagascar's basically Austronesian language, which contains loan words from coastal Kenyan Bantu languages. But there are no corresponding Austronesian loan words in Kenyan languages, and other traces of Austronesians are very thin on the ground in East Africa: mainly just Africa's possible legacy of Indonesian musical instruments (xylophones and zithers) and, of course, the Austronesian crops that became so important in African agriculture. Hence one wonders whether Austronesians, instead of taking the easier route to Madagascar via India and East Africa, somehow (incredibly) sailed straight across the Indian Ocean, discovered Madagascar, and only later got plugged into East African trade routes. Thus, some mystery remains about Africa's most surprising fact of human geography.

WHAT CAN ARCHAEOLOGY tell us about the other great population movement in recent African prehistory-the Bantu expansion? We saw from the twin evidence of modern peoples and their languages that sub-Saharan Africa was not always a black continent, as we think of it today. Instead, this evidence suggested that Pygmies had once been widespread in the rain forest of Central Africa, while Khoisan peoples had been widespread in drier parts of subequatorial Africa. Can archaeology test those a.s.sumptions? tell us about the other great population movement in recent African prehistory-the Bantu expansion? We saw from the twin evidence of modern peoples and their languages that sub-Saharan Africa was not always a black continent, as we think of it today. Instead, this evidence suggested that Pygmies had once been widespread in the rain forest of Central Africa, while Khoisan peoples had been widespread in drier parts of subequatorial Africa. Can archaeology test those a.s.sumptions?

In the case of the Pygmies, the answer is "not yet," merely because archaeologists have yet to discover ancient human skeletons from the Central African forests. For the Khoisan, the answer is "yes." In Zambia, to the north of the modern Khoisan range, archaeologists have found skulls of people possibly resembling the modern Khoisan, as well as stone tools resembling those that Khoisan peoples were still making in southern Africa at the time Europeans arrived.

As for how the Bantu came to replace those northern Khoisan, archaeological and linguistic evidence suggest that the expansion of ancestral Bantu farmers from West Africa's inland savanna south into its wetter coastal forest may have begun as early as 3000 B.C. B.C. (Figure 19.4). Words still widespread in all Bantu languages show that, already then, the Bantu had cattle and wet-climate crops such as yams, but that they lacked metal and were still engaged in much fishing, hunting, and gathering. They even lost their cattle to disease borne by tsetse flies in the forest. As they spread into the Congo Basin's equatorial forest zone, cleared gardens, and increased in numbers, they began to engulf the Pygmy hunter-gatherers and compress them into the forest itself. (Figure 19.4). Words still widespread in all Bantu languages show that, already then, the Bantu had cattle and wet-climate crops such as yams, but that they lacked metal and were still engaged in much fishing, hunting, and gathering. They even lost their cattle to disease borne by tsetse flies in the forest. As they spread into the Congo Basin's equatorial forest zone, cleared gardens, and increased in numbers, they began to engulf the Pygmy hunter-gatherers and compress them into the forest itself.

By soon after 1000 B.C. B.C. the Bantu had emerged from the eastern side of the forest into the more open country of East Africa's Rift Valley and Great Lakes. Here they encountered a melting pot of Afroasiatic and Nilo-Saharan farmers and herders growing millet and sorghum and raising livestock in drier areas, along with Khoisan hunter-gatherers. Thanks to their wet-climate crops inherited from their West African homeland, the Bantu were able to farm in wet areas of East Africa unsuitable for all those previous occupants. By the last centuries the Bantu had emerged from the eastern side of the forest into the more open country of East Africa's Rift Valley and Great Lakes. Here they encountered a melting pot of Afroasiatic and Nilo-Saharan farmers and herders growing millet and sorghum and raising livestock in drier areas, along with Khoisan hunter-gatherers. Thanks to their wet-climate crops inherited from their West African homeland, the Bantu were able to farm in wet areas of East Africa unsuitable for all those previous occupants. By the last centuries B.C. B.C. the advancing Bantu had reached the East African coast. the advancing Bantu had reached the East African coast.

In East Africa the Bantu began to acquire millet and sorghum (along with the Nilo-Saharan names for those crops), and to reacquire cattle, from their Nilo-Saharan and Afroasiatic neighbors. They also acquired iron, which had just begun to be smelted in Africa's Sahel zone. The origins of ironworking in sub-Saharan Africa soon after 1000 B.C. B.C. are still unclear. That early date is suspiciously close to dates for the arrival of Near Eastern ironworking techniques in Carthage, on the North African coast. Hence historians often a.s.sume that knowledge of metallurgy reached sub-Saharan Africa from the north. On the other hand, copper smelting had been going on in the West African Sahara and Sahel since at least 2000 are still unclear. That early date is suspiciously close to dates for the arrival of Near Eastern ironworking techniques in Carthage, on the North African coast. Hence historians often a.s.sume that knowledge of metallurgy reached sub-Saharan Africa from the north. On the other hand, copper smelting had been going on in the West African Sahara and Sahel since at least 2000 B.C. B.C. That could have been the precursor to an independent African discovery of iron metallurgy. Strengthening that hypothesis, the iron-smelting techniques of smiths in sub-Saharan Africa were so different from those of the Mediterranean as to suggest independent development: African smiths discovered how to produce high temperatures in their village furnaces and manufacture steel over 2,000 years before the Bessemer furnaces of 19th-century Europe and America. That could have been the precursor to an independent African discovery of iron metallurgy. Strengthening that hypothesis, the iron-smelting techniques of smiths in sub-Saharan Africa were so different from those of the Mediterranean as to suggest independent development: African smiths discovered how to produce high temperatures in their village furnaces and manufacture steel over 2,000 years before the Bessemer furnaces of 19th-century Europe and America.

With the addition of iron tools to their wet-climate crops, the Bantu had finally put together a military-industrial package that was unstoppable in the subequatorial Africa of the time. In East Africa they still had to compete against numerous Nilo-Saharan and Afroasiatic Iron Age farmers. But to the south lay 2,000 miles of country thinly occupied by Khoisan hunter-gatherers, lacking iron and crops. Within a few centuries, in one of the swiftest colonizing advances of recent prehistory, Bantu farmers had swept all the way to Natal, on the east coast of what is now South Africa.

It's easy to oversimplify what was undoubtedly a rapid and dramatic expansion, and to picture all Khoisan in the way being trampled by onrushing Bantu hordes. In reality, things were more complicated. Khoisan peoples of southern Africa had already acquired sheep and cattle a few centuries ahead of the Bantu advance. The first Bantu pioneers probably were few in number, selected wet-forest areas suitable for their yam agriculture, and leapfrogged over drier areas, which they left to Khoisan herders and hunter-gatherers. Trading and marriage relationships were undoubtedly established between those Khoisan and the Bantu farmers, each occupying different adjacent habitats, just as Pygmy hunter-gatherers and Bantu farmers still do today in equatorial Africa. Only gradually, as the Bantu multiplied and incorporated cattle and dry-climate cereals into their economy, did they fill in the leapfrogged areas. But the eventual result was still the same: Bantu farmers occupying most of the former Khoisan realm; the legacy of those former Khoisan inhabitants reduced to clicks in scattered non-Khoisan languages, as well as buried skulls and stone tools waiting for archaeologists to discover; and the Khoisan-like appearance of some southern African Bantu peoples.

What actually happened to all those vanished Khoisan populations? We don't know. All we can say for sure is that, in places where Khoisan peoples had lived for perhaps tens of thousands of years, there are now Bantu. We can only venture a guess, by a.n.a.logy with witnessed events in modern times when steel-toting white farmers collided with stone tool-using hunter-gatherers of Aboriginal Australia and Indian California. There, we know that hunter-gatherers were rapidly eliminated in a combination of ways: they were driven out, men were killed or enslaved, women were appropriated as wives, and both s.e.xes became infected with epidemics of the farmers' diseases. An example of such a disease in Africa is malaria, which is borne by mosquitoes that breed around farmers' villages, and to which the invading Bantu had already developed genetic resistance but Khoisan hunter-gatherers probably had not.

However, Figure 19.1, of recent African human distributions, reminds us that the Bantu did not overrun all the Khoisan, who did survive in southern African areas unsuitable for Bantu agriculture. The southernmost Bantu people, the Xhosa, stopped at the Fish River on South Africa's south coast, 500 miles east of Cape Town. It's not that the Cape of Good Hope itself is too dry for agriculture: it is, after all, the breadbasket of modern South Africa. Instead, the Cape has a Mediterranean climate of winter rains, in which the Bantu summer-rain crops do not grow. By 1652, the year the Dutch arrived at Cape Town with their winter-rain crops of Near Eastern origin, the Xhosa had still not spread beyond the Fish River.

That seeming detail of plant geography had enormous implications for politics today. One consequence was that, once South African whites had quickly killed or infected or driven off the Cape's Khoisan population, whites could claim correctly that they had occupied the Cape before the Bantu and thus had prior rights to it. That claim needn't be taken seriously, since the prior rights of the Cape Khoisan didn't inhibit whites from dispossessing them. The much heavier consequence was that the Dutch settlers in 1652 had to contend only with a spa.r.s.e population of Khoisan herders, not with a dense population of steel-equipped Bantu farmers. When whites finally spread east to encounter the Xhosa at the Fish River in 1702, a period of desperate fighting began. Even though Europeans by then could supply troops from their secure base at the Cape, it took nine wars and 175 years for their armies, advancing at an average rate of less than one mile per year, to subdue the Xhosa. How could whites have succeeded in establishing themselves at the Cape at all, if those first few arriving Dutch ships had faced such fierce resistance?

Thus, the problems of modern South Africa stem at least in part from a geographic accident. The homeland of the Cape Khoisan happened to contain few wild plants suitable for domestication; the Bantu happened to inherit summer-rain crops from their ancestors of 5,000 years ago; and Europeans happened to inherit winter-rain crops from their ancestors of nearly 10,000 years ago. Just as the sign "Goering Street" in the capital of newly independent Namibia reminded me, Africa's past has stamped itself deeply on Africa's present.

THAT'S HOW THE Bantu were able to engulf the Khoisan, instead of vice versa. Now let's turn to the remaining question in our puzzle of African prehistory: why Europeans were the ones to colonize sub-Saharan Africa. That it was not the other way around is especially surprising, because Africa was the sole cradle of human evolution for millions of years, as well as perhaps the homeland of anatomically modern Bantu were able to engulf the Khoisan, instead of vice versa. Now let's turn to the remaining question in our puzzle of African prehistory: why Europeans were the ones to colonize sub-Saharan Africa. That it was not the other way around is especially surprising, because Africa was the sole cradle of human evolution for millions of years, as well as perhaps the homeland of anatomically modern h.o.m.o sapiens h.o.m.o sapiens. To these advantages of Africa's enormous head start were added those of highly diverse climates and habitats and of the world's highest human diversity. An extraterrestrial visiting Earth 10,000 years ago might have been forgiven for predicting that Europe would end up as a set of va.s.sal states of a sub-Saharan African empire.

The proximate reasons behind the outcome of Africa's collision with Europe are clear. Just as in their encounter with Native Americans, Europeans entering Africa enjoyed the triple advantage of guns and other technology, widespread literacy, and the political organization necessary to sustain expensive programs of exploration and conquest. Those advantages manifested themselves almost as soon as the collisions started: barely four years after Vasco da Gama first reached the East African coast, in 1498, he returned with a fleet bristling with cannons to compel the surrender of East Africa's most important port, Kilwa, which controlled the Zimbabwe gold trade. But why did Europeans develop those three advantages before sub-Saharan Africans could?

As we have discussed, all three arose historically from the development of food production. But food production was delayed in sub-Saharan Africa (compared with Eurasia) by Africa's paucity of domesticable native animal and plant species, its much smaller area suitable for indigenous food production, and its north-south axis, which r.e.t.a.r.ded the spread of food production and inventions. Let's examine how those factors operated.

First, as regards domestic animals, we've already seen that those of sub-Saharan Africa came from Eurasia, with the possible exception of a few from North Africa. As a result, domestic animals did not reach sub-Saharan Africa until thousands of years after they began to be utilized by emerging Eurasian civilizations. That's initially surprising, because we think of Africa as the the continent of big wild mammals. But we saw in Chapter 9 that a wild animal, to be domesticated, must be sufficiently docile, submissive to humans, cheap to feed, and immune to diseases and must grow rapidly and breed well in captivity. Eurasia's native cows, sheep, goats, horses, and pigs were among the world's few large wild animal species to pa.s.s all those tests. Their African equivalents-such as the African buffalo, zebra, bush pig, rhino, and hippopotamus-have never been domesticated, not even in modern times. continent of big wild mammals. But we saw in Chapter 9 that a wild animal, to be domesticated, must be sufficiently docile, submissive to humans, cheap to feed, and immune to diseases and must grow rapidly and breed well in captivity. Eurasia's native cows, sheep, goats, horses, and pigs were among the world's few large wild animal species to pa.s.s all those tests. Their African equivalents-such as the African buffalo, zebra, bush pig, rhino, and hippopotamus-have never been domesticated, not even in modern times.

It's true, of course, that some large African animals have occasionally been tamed tamed. Hannibal enlisted tamed African elephants in his unsuccessful war against Rome, and ancient Egyptians may have tamed giraffes and other species. But none of those tamed animals was actually domesticated-that is, selectively bred in captivity and genetically modified so as to become more useful to humans. Had Africa's rhinos and hippos been domesticated and ridden, they would not only have fed armies but also have provided an unstoppable cavalry to cut through the ranks of European hors.e.m.e.n. Rhino-mounted Bantu shock troops could have overthrown the Roman Empire. It never happened.

A second factor is a corresponding, though less extreme, disparity between sub-Saharan Africa and Eurasia in domesticable plants. The Sahel, Ethiopia, and West Africa did yield indigenous crops, but many fewer varieties than grew in Eurasia. Because of the limited variety of wild starting material suitable for plant domestication, even Africa's earliest agriculture may have begun several thousand years later than that of the Fertile Crescent.

Thus, as far as plant and animal domestication was concerned, the head start and high diversity lay with Eurasia, not with Africa. A third factor is that Africa's area is only about half that of Eurasia. Furthermore, only about one-third of its area falls within the sub-Saharan zone north of the equator that was occupied by farmers and herders before 1000 B.C. B.C. Today, the total population of Africa is less than 700 million, compared with 4 billion for Eurasia. But, all other things being equal, more land and more people mean more competing societies and inventions, hence a faster pace of development. Today, the total population of Africa is less than 700 million, compared with 4 billion for Eurasia. But, all other things being equal, more land and more people mean more competing societies and inventions, hence a faster pace of development.

The remaining factor behind Africa's slower rate of post-Pleistocene development compared with Eurasia's is the different orientation of the main axes of these continents. Like that of the Americas, Africa's major axis is north-south, whereas Eurasia's is east-west (Figure 10.1). As one moves along a north-south axis, one traverses zones differing greatly in climate, habitat, rainfall, day length, and diseases of crops and livestock. Hence, crops and animals domesticated or acquired in one part of Africa had great difficulty in moving to other parts. In contrast, crops and animals moved easily between Eurasian societies thousands of miles apart but at the same lat.i.tude and sharing similar climates and day lengths.

The slow pa.s.sage or complete halt of crops and livestock along Africa's north-south axis had important consequences. For example, the Mediterranean crops that became Egypt's staples require winter rains and seasonal variation in day length for their germination. Those crops were unable to spread south of the Sudan, beyond which they encountered summer rains and little or no seasonal variation in daylight. Egypt's wheat and barley never reached the Mediterranean climate at the Cape of Good Hope until European colonists brought them in 1652, and the Khoisan never developed agriculture. Similarly, the Sahel crops adapted to summer rain and to little or no seasonal variation in day length were brought by the Bantu into southern Africa but could not grow at the Cape itself, thereby halting the advance of Bantu agriculture. Bananas and other tropical Asian crops for which Africa's climate is eminently suitable, and which today are among the most productive staples of tropical African agriculture, were unable to reach Africa by land routes. They apparently did not arrive until the first millennium A.D. A.D., long after their domestication in Asia, because they had to wait for large-scale boat traffic across the Indian Ocean.

Africa's north-south axis also seriously impeded the spread of livestock. Equatorial Africa's tsetse flies, carrying trypanosomes to which native African wild mammals are resistant, proved devastating to introduced Eurasian and North African species of livestock. The cows that the Bantu acquired from the tsetse-free Sahel zone failed to survive the Bantu expansion through the equatorial forest. Although horses had already reached Egypt around 1800 B.C. B.C. and transformed North African warfare soon thereafter, they did not cross the Sahara to drive the rise of cavalry-mounted West African kingdoms until the first millennium and transformed North African warfare soon thereafter, they did not cross the Sahara to drive the rise of cavalry-mounted West African kingdoms until the first millennium A.D. A.D., and they never spread south through the tsetse fly zone. While cattle, sheep, and goats had already reached the northern edge of the Serengeti in the third millennium B.C. B.C., it took more than 2,000 years beyond that for livestock to cross the Serengeti and reach southern Africa.

Similarly slow in spreading down Africa's north-south axis was human technology. Pottery, recorded in the Sudan and Sahara around 8000 B.C. B.C., did not reach the Cape until around A.D. A.D. 1. Although writing developed in Egypt by 3000 1. Although writing developed in Egypt by 3000 B.C. B.C. and spread in an alphabetized form to the Nubian kingdom of Meroe, and although alphabetic writing reached Ethiopia (possibly from Arabia), writing did not arise independently in the rest of Africa, where it was instead brought in from the outside by Arabs and Europeans. and spread in an alphabetized form to the Nubian kingdom of Meroe, and although alphabetic writing reached Ethiopia (possibly from Arabia), writing did not arise independently in the rest of Africa, where it was instead brought in from the outside by Arabs and Europeans.

In short, Europe's colonization of Africa had nothing to do with differences between European and African peoples themselves, as white racists a.s.sume. Rather, it was due to accidents of geography and biogeography-in particular, to the continents' different areas, axes, and suites of wild plant and animal species. That is, the different historical trajectories of Africa and Europe stem ultimately from differences in real estate.

EPILOGUE THE FUTURE OF HUMAN HISTORY AS A SCIENCE

YALI'S QUESTION WENT TO THE HEART OF THE CURRENT human condition, and of post-Pleistocene human history. Now that we have completed this brief tour over the continents, how shall we answer Yali? human condition, and of post-Pleistocene human history. Now that we have completed this brief tour over the continents, how shall we answer Yali?

I would say to Yali: the striking differences between the long-term histories of peoples of the different continents have been due not to innate differences in the peoples themselves but to differences in their environments. I expect that if the populations of Aboriginal Australia and Eurasia could have been interchanged during the Late Pleistocene, the original Aboriginal Australians would now be the ones occupying most of the Americas and Australia, as well as Eurasia, while the original Aboriginal Eurasians would be the ones now reduced to downtrodden population fragments in Australia. One might at first be inclined to dismiss this a.s.sertion as meaningless, because the experiment is imaginary and my claim about its outcome cannot be verified. But historians are nevertheless able to evaluate related hypotheses by retrospective tests. For instance, one can examine what did happen when European farmers were transplanted to Greenland or the U.S. Great Plains, and when farmers stemming ultimately from China emigrated to the Chatham Islands, the rain forests of Borneo, or the volcanic soils of Java or Hawaii. These tests confirm that the same ancestral peoples either ended up extinct, or returned to living as hunter-gatherers, or went on to build complex states, depending on their environments. Similarly, Aboriginal Australian hunter-gatherers, variously transplanted to Flinders Island, Tasmania, or southeastern Australia, ended up extinct, or as hunter-gatherers with the modern world's simplest technology, or as ca.n.a.l builders intensively managing a productive fishery, depending on their environments.

Of course, the continents differ in innumerable environmental features affecting trajectories of human societies. But a mere laundry list of every possible difference does not const.i.tute an answer to Yali's question. Just four sets of differences appear to me to be the most important ones.

The first set consists of continental differences in the wild plant and animal species available as starting materials for domestication. That's because food production was critical for the acc.u.mulation of food surpluses that could feed non-food-producing specialists, and for the buildup of large populations enjoying a military advantage through mere numbers even before they had developed any technological or political advantage. For both of those reasons, all developments of economically complex, socially stratified, politically centralized societies beyond the level of small nascent chiefdoms were based on food production.

But most wild animal and plant species have proved unsuitable for domestication: food production has been based on relatively few species of livestock and crops. It turns out that the number of wild candidate species for domestication varied greatly among the continents, because of differences in continental areas and also (in the case of big mammals) in Late Pleistocene extinctions. These extinctions were much more severe in Australia and the Americas than in Eurasia or Africa. As a result, Africa ended up biologically somewhat less well endowed than the much larger Eurasia, the Americas still less so, and Australia even less so, as did Yali's New Guinea (with one-seventieth of Eurasia's area and with all of its original big mammals extinct in the Late Pleistocene).

On each continent, animal and plant domestication was concentrated in a few especially favorable homelands accounting for only a small fraction of the continent's total area. In the case of technological innovations and political inst.i.tutions as well, most societies acquire much more from other societies than they invent themselves. Thus, diffusion and migration within a continent contribute importantly to the development of its societies, which tend in the long run to share each other's developments (insofar as environments permit) because of the processes ill.u.s.trated in such simple form by Maori New Zealand's Musket Wars. That is, societies initially lacking an advantage either acquire it from societies possessing it or (if they fail to do so) are replaced by those other societies.

Hence a second set of factors consists of those affecting rates of diffusion and migration, which differed greatly among continents. They were most rapid in Eurasia, because of its east-west major axis and its relatively modest ecological and geographical barriers. The reasoning is straightforward for movements of crops and livestock, which depend strongly on climate and hence on lat.i.tude. But similar reasoning also applies to the diffusion of technological innovations, insofar as they are best suited without modification to specific environments. Diffusion was slower in Africa and especially in the Americas, because of those continents' north-south major axes and geographic and ecological barriers. It was also difficult in traditional New Guinea, where rugged terrain and the long backbone of high mountains prevented any significant progress toward political and linguistic unification.

Related to these factors affecting diffusion within within continents is a third set of factors influencing diffusion continents is a third set of factors influencing diffusion between between continents, which may also help build up a local pool of domesticates and technology. Ease of intercontinental diffusion has varied, because some continents are more isolated than others. Within the last 6,000 years it has been easiest from Eurasia to sub-Saharan Africa, supplying most of Africa's species of livestock. But interhemispheric diffusion made no contribution to Native America's complex societies, isolated from Eurasia at low lat.i.tudes by broad oceans, and at high lat.i.tudes by geography and by a climate suitable just for hunting-gathering. To Aboriginal Australia, isolated from Eurasia by the water barriers of the Indonesian Archipelago, Eurasia's sole proven contribution was the dingo. continents, which may also help build up a local pool of domesticates and technology. Ease of intercontinental diffusion has varied, because some continents are more isolated than others. Within the last 6,000 years it has been easiest from Eurasia to sub-Saharan Africa, supplying most of Africa's species of livestock. But interhemispheric diffusion made no contribution to Native America's complex societies, isolated from Eurasia at low lat.i.tudes by broad oceans, and at high lat.i.tudes by geography and by a climate suitable just for hunting-gathering. To Aboriginal Australia, isolated from Eurasia by the water barriers of the Indonesian Archipelago, Eurasia's sole proven contribution was the dingo.

The fourth and last set of factors consists of continental differences in area or total population size. A larger area or population means more potential inventors, more competing societies, more innovations available to adopt-and more pressure to adopt and retain innovations, because societies failing to do so will tend to be eliminated by competing societies. That fate befell African pygmies and many other hunter-gatherer populations displaced by farmers. Conversely, it also befell the stubborn, conservative Greenland Norse farmers, replaced by Eskimo hunter-gatherers whose subsistence methods and technology were far superior to those of the Norse under Greenland conditions. Among the world's landma.s.ses, area and the number of competing societies were largest for Eurasia, much smaller for Australia and New Guinea and especially for Tasmania. The Americas, despite their large aggregate area, were fragmented by geography and ecology and functioned effectively as several poorly connected smaller continents.

Those four sets of factors const.i.tute big environmental differences that can be quantified objectively and that are not subject to dispute. While one can contest my subjective impression that New Guineans are on the average smarter than Eurasians, one cannot deny that New Guinea has a much smaller area and far fewer big animal species than Eurasia. But mention of these environmental differences invites among historians the label "geographic determinism," which raises hackles. The label seems to have unpleasant connotations, such as that human creativity counts for nothing, or that we humans are pa.s.sive robots helplessly programmed by climate, fauna, and flora. Of course these fears are misplaced. Without human inventiveness, all of us today would still be cutting our meat with stone tools and eating it raw, like our ancestors of a million years ago. All human societies contain inventive people. It's just that some environments provide more starting materials, and more favorable conditions for utilizing inventions, than do other environments.

THESE ANSWERS TO Yali's question are longer and more complicated than Yali himself would have wanted. Historians, however, may find them too brief and oversimplified. Compressing 13,000 years of history on all continents into a 400-page book works out to an average of about one page per continent per 150 years, making brevity and simplification inevitable. Yet the compression brings a compensating benefit: long-term comparisons of regions yield insights that cannot be won from short-term studies of single societies. Yali's question are longer and more complicated than Yali himself would have wanted. Historians, however, may find them too brief and oversimplified. Compressing 13,000 years of history on all continents into a 400-page book works out to an average of about one page per continent per 150 years, making brevity and simplification inevitable. Yet the compression brings a compensating benefit: long-term comparisons of regions yield insights that cannot be won from short-term studies of single societies.

Naturally, a host of issues raised by Yali's question remain unresolved. At present, we can put forward some partial answers plus a research agenda for the future, rather than a fully developed theory. The challenge now is to develop human history as a science, on a par with acknowledged historical sciences such as astronomy, geology, and evolutionary biology. Hence it seems appropriate to conclude this book by looking to the future of the discipline of history, and by outlining some of the unresolved issues.

The most straightforward extension of this book will be to quantify further, and thus to establish more convincingly the role of, intercontinental differences in the four sets of factors that appear to be most important. To ill.u.s.trate differences in starting materials for domestication, I provided numbers for each continent's total of large wild terrestrial mammalian herbivores and omnivores (Table 9.2) and of large-seeded cereals (Table 8.1). One extension would be to a.s.semble corresponding numbers for large-seeded legumes (pulses), such as beans, peas, and vetches. In addition, I mentioned factors disqualifying big mammalian candidates for domestication, but I did not tabulate how many candidates are disqualified by each factor on each continent. It would be interesting to do so, especially for Africa, where a higher percentage of candidates is disqualified than in Eurasia: which disqualifying factors are most important in Africa, and what has selected for their high frequency in African mammals? Quant.i.tative data should also be a.s.sembled to test my preliminary calculations suggesting differing rates of diffusion along the major axes of Eurasia, the Americas, and Africa.