In some cases, we have fairly detailed records of Ashkenazi commercial activity. For example, concerning the Jews of Rous- silon circa 1270: "The evidence is overwhelming that this rather substantial group of Jews supported itself by money lending, to the virtual exclusion of all other economic activities. Of the 228 adult male Jews mentioned in the registers, almost 80 percent appear as lenders to their Christian neighbors. Nor were loans by Jewish women (mostly widows) uncommon, and the capital of minors was often invested in a similar manner. Moreover, the Jews most active as moneylenders appear to have been the most respected members of the community."16
The Jews in this period were prosperous. Historian H. Ben- Sasson pointed out that "Western Europe suffered virtual famine for many years in the tenth and eleventh centuries, [but] there is no hint or echo of this in the Jewish sources of the region in this period. The city dweller lived at an aristocratic level, as befitted international merchants and honored local financiers."17 Their standard of living was that of the lower nobility.18 The Ashkenazi Jews were thus spared malnutrition and occasional famine. This helped Jewish populations recover from their losses due to persecution; it may have affected selective pressures as well.
And persecution was a very serious matter. Although the Jews of this region were prosperous, they were not safe. The first major crisis was the First Crusade of 1096, which resulted in thedeaths of something like a quarter of the Jews in the Rhineland. Religious hostility, probably exacerbated by commercial rivalries, increased in Europe during this period, manifesting itself in the form of massacres and expulsions. This pattern of persecution kept the Ashkenazi Jews from overflowing their white-collar niche during the High Middle Ages, which otherwise would have happened fairly rapidly. It culminated in the expulsion of the Jews from most of Western Europe—from England in 1290, from France in 1394, and from various regions of Germany in the fifteenth century. The expulsions had greater effect on the demography of the region, in the long run, than massacres and persecutions. Jewish population growth rates were high due to both their prosperity and their belief system, as they favored large families, so their numbers tended to recover from attacks after a generation or two. But the potential for recovery decreased as Jews were excluded from more and more of Western Europe.
Many of the Jews who were expelled moved east, first to Austria, Bohemia, and Moravia, and later to the Polish- Lithuanian Commonwealth. The Polish rulers welcomed Jewish immigrants who could help modernize and reconstruct the country, which had been devastated by Mongol raids. Jews were welcomed as urban developers, investors, and initiators of trade. Other skilled immigrants were also welcomed, but some of those groups brought political risks, particularly the Germans because of their connection with the Teutonic Knights. The Jews were politically neutral and therefore safe.
As had been the case in Western Europe, the Jews of Poland had a very unusual occupational profile. None were farmers, and few were craftsmen, at least in the early centuries of that settlement. The very first to immigrate were mainlymoneylenders, but that soon changed. They became tax-farmers (something like a freelance tax collector), toll-farmers, estate managers, and proprietors of mills and taverns. According to the historian B. D. Weinryb, in the middle of the fourteenth century "about 15 percent of the Jewish population were earners of wages, salaries and fees. The rest were independent owners of business enterprises."19 They were the management class of the Polish-Lithuanian Commonwealth. Besides literacy, success in those specialized occupations depended upon skills similar to those of businessmen today, not least the ability to keep track of complex transactions and money flows.
Eventually, as the Ashkenazi population of the Polish- Lithuanian Commonwealth increased, more and more Jews became craftsmen—there are, after all, only so many managerial and financial slots. Still, for 800 to 900 years, from roughly 800 to 1650 or 1700, the great majority of the Ashkenazi Jews had managerial and financial jobs, jobs of high complexity, and were neither farmers nor craftsmen. In this they differed from all other settled peoples of which we have knowledge. In fact, it would have been impossible (back then) for the majority of any territorial ethnic group to have such white-collar jobs, because agricultural productivity would have been too low. Ninety percent of the population had to farm in order to produce enough to feed themselves and a thin crust of rulers, scribes, soldiers, craftsmen, and merchants. Selection for success at white-collar tasks could only have occurred if those scribes and merchants could somehow become an ethnic group, one defined by occupation rather than location.
Jews who were particularly good at these high-complexity jobs enjoyed increased reproductive success. As Weinryb noted: "More children survived to adulthood in affluent families thanin less affluent ones. A number of genealogies of business leaders, prominent rabbis, community leaders, and the like—generally belonging to the more affluent classes—show that such people often had four, six, sometimes even eight or nine children who reached adulthood. . . . On the other hand, there are some indications that poorer families tended to be small ones. ... It should also be added that overcrowding, which favors epidemics, was more prevalent among the poorer classes."20 In short, Weinryb wrote, "the number of children surviving among Polish Jews seems to have varied considerably from one social level to another."21 He also suggested that wealthier Jews were less crowded, as they lived in bigger houses; could keep their houses warmer; could afford wet-nurses; and had better access to rural refuges from epidemics. As an example, he cites a census of the town of Brody in 1764 showing that homeowner households had 1.2 children per adult member, while tenant households had 0.6.22
The occupational pattern of the Jews living in the Islamic world was different from that of the Ashkenazim. The Jews of Islam did not have a high concentration of white-collar occupations. Some had such jobs in some parts of the Islamic world, in some periods, but it seems it was never the case that most did in any given place and time. In part this was because other minority groups—Greek Christians, Armenians, and so on— competed successfully for these jobs, and in part it was because Muslims, valuing nonwarrior occupations more highly than medieval Christians did, took many of those jobs themselves. In addition, because there was less persecution overall, there were many more Jews in the Islamic world than in Europe—more Jews, in fact, than there were white-collar jobs.
In fact, to a large extent, and especially during years of relative Muslim decline from the fourteenth to the twentieth centuries, the Jews of Islam tended to have "dirty" jobs.23 These included such tasks as cleaning cesspools and drying the contents for use as fuel—a common Jewish occupation in Morocco, Yemen, Iraq, Iran, and Central Asia. Jews were also found as tanners, butchers, and hangmen and in other disagreeable or despised occupations. Such jobs must have had low IQ elasticity: Brilliant tanners and hangmen almost certainly did not become rich.
EMERGENCE OF INTELLECTUAL DIFFERENCES
The selection process we are interested in may have been under way during the Middle Ages, but its results were not yet evident in 1800. Of course, there were no IQtests then, but there were as yet no Ashkenazi discoveries in science or mathematics either.
Perhaps if anti-Semitism had not prevented Jews from a wide range of career choices, this would not have been the case. Severe restrictions on Jewish occupations and participation in public life were just beginning to be lifted. But another reason they were not found among the early European scientists and mathematicians was that the Ashkenazim had been uninterested in natural philosophy for some centuries. Indeed, at times Ashkenazi leaders were positively hostile to such inquiries. Ever since the work of Maimonides in the twelfth century, the majority of Jewish religious leaders had tended to subordinate philosophy to the literal interpretation of the Torah (the first five books of the Hebrew Bible).
A herem, or religious ban, had been placed on Maimonides' philosophical work after his death in 1204, while Solomon ben
Abraham Adret, a rabbi and scholar at the beginning of t
he fourteenth century, issued another herem on "any member of the community who, being under twenty-five years, shall study the works of the Greeks on natural science and meta- physics."24 Although the Ashkenazim put a tremendous amount of intellectual energy into Talmudic analysis during this period, we do not believe that the resulting body of work provides evidence of unusual mental acuity. Despite its historical significance and its importance to the Jewish culture and religion, it is fair to say that it hasn't drawn a great deal of interest outside of the Jewish community.
Another factor is that the Ashkenazi Jews were in the wrong place: Science and technology were sprouting in Western Europe, not in the Polish-Lithuanian Commonwealth. In fact, the Jews had been welcomed because Eastern Europe was backward and therefore in need of their skills.
All of these factors had begun to change by 1800. In 1791, France became the first country in Europe to grant legal equality to the Jews, and Napoleon's conquests spread that policy over much of Europe. Even in countries without full civil equality, such as Great Britain, Jews generally enjoyed increased rights. Movements within Judaism began to support Enlightenment values and escape from the ghetto, and things began to happen. As the British historian Eric Hobsbawm has said, "It is as though the lid had been removed from a pressure cooker."25
A trickle of Ashkenazi scientists and mathematicians began to appear in the first half of the nineteenth century—major talents like the eminent mathematicians Carl Jacobi and Leopold Kronecker. They originated in Germany, home to a comparatively small fraction of the Ashkenazim. Over time, more significant Jewish figures appeared in the arts and sciences. This might have happened more rapidly, except that the majority of Jews (after the partition of Poland) lived in Russia, which was slow to emancipate. Many Ashkenazim from Eastern Europe emigrated—some to Western Europe and some to the United States, Canada, Argentina, and South Africa. In those new lands they were much freer to exercise their talents, and by the beginning of the twentieth century, Ashkenazi Jews were playing a major role in all areas of science and mathematics. This trend strengthened in the second half of the twentieth century— even though the Nazis had murdered most of the Ashkenazim remaining in Europe—and it continues today.
A GENETICALLY DISTINCT GROUP
One standard counterargument to any thesis suggesting that the Ashkenazi Jews are in some way biologically different or special is that they are adherents of a religion rather than a race or ethnic group in the strictest sense, and that therefore they cannot be genetically distinct. Some have brought up conversion as a mixing mechanism, often mentioning Elizabeth Taylor or Sammy Davis Jr., prominent converts to Judaism, as contemporary examples. Raphael and Jennifer Patai argued in The Myth of the Jewish Race that an inflow of genes from neighboring populations, via conversion, intermarriage, and illicit sex, kept Jewish populations from developing distinct genetic features.26 It's true that Jews as a whole are not a single genetically distinct group; however, some subgroups are—in particular, the Ashke- nazim. Strong evidence exists in the prevalence of genetic diseases like Tay-Sachs and others, but there is much moreinformation these days as a result of new technologies for studying DNA. Take a look: SNPs don't lie.27
The plot shown on page 205 makes use of those alleles that are considerably more common in one group than in others to determine group membership. Ashkenazi Jews (represented by circles and squares, the cluster in the upper-right- hand corner) can easily be distinguished from the general European population (triangles). Irish, Scandinavians, Germans, and Brits occupy the upper left end of the archipelago, while Greeks and Italians are found at the lower left end. The Ashkenazi Jews are a distinct group; this is made especially clear by the cluster of dark squares, the group of Ashkenazi Jews with four Ashkenazi Jewish grandparents. For a very long time, Ashkenazi Jews (and most other Jewish groups as well) were endogamous, rarely marrying outside their faith or accepting converts. An endogamous group can remain genetically distinct, or become genetically different from neighboring peoples, if that social pattern persists. This is especially likely if some major fraction of the group's ancestors came from somewhere else (in this case, the Middle East) or if the selective pressures they've experienced have been different from those present in neighboring peoples.
There is reason to believe that a fair fraction («40 percent) of Ashkenazi ancestry is European, which we will discuss later, but it seems that for the most part those genes were added to the mix a long time ago, possibly back in the days of the Roman Empire. That notion is inherently plausible because many of the Jews in Rome arrived as enslaved prisoners of war, captured in the Great Revolt of AD 65-73 or in Bar-Kochba's revolt of AD 132-135. Many of those slaves eventually became freemen, and
European genetic substructure analysis
it is likely that they were predominantly male. Many must have married local European women. There should therefore be a significant southern European component in the maternal ancestry of Roman Jews and, later, Ashkenazi Jews.
Admixture has not kept the Ashkenazim from becoming genetically distinct. Even if a population starts out as a mixture of two peoples, as in this case, becoming endogamous (ending intermarriage) and staying so for a long time ensures that the population will become homogeneous. If the population's ancestry is 60 percent Middle Eastern and 40 percent European, for example, a few dozen generations of endogamy will result in a population in which each individual's ancestry is quite close to 60 percent Middle Eastern and 40 percent European. In other words, you eventually get a population that has a flavor all its own—even more so if it experiences special selective pressures.
This means that if you look at the most informative parts of the genome, you can tell whether a certain individual is Ashkenazi (as opposed to, say, a non-Jewish Italian, Greek, or German) just about every time, particularly if all his or her recent ancestors are Jewish. In the plot, the circles represent Ashkenazi Jewish individuals, but the shaded circles represent individuals whose grandparents were all Ashkenazi Jews as well. That distinction matters, because Jews haven't been nearly as endogamous over the past century as they were during the Middle Ages.
Could these same methods distinguish the Ashkenazi from other Jewish groups, such as Moroccan Jews or Yemeni Jews? The answer is almost certainly yes. Although that particular measurement has not yet been made, it should be easy to make that distinction because the genetic distance between Ashkenazi Jews and Yemeni Jews is considerably larger than that between Ashkenazi Jews and Western Europeans.
Members of the general public sometimes believe that individual genetic profiles do not necessarily reflect nationality. Somebody who is Swedish, for example, might be genetically closer to someone from Japan than to another Swede, according to this view of things. If this was true, it would apply to a group like the Ashkenazi Jews as well, even though they are not quite a "nationality." However, that belief is false. In fact, a case where a person of one nationality is closer genetically to someone of a distant nationality than to his or her own compatriots never happens. If you're Swedish, every Swede (not counting recent immigrants) is genetically closer to you than any person in Japan.
It's possible to be closer to someone in Japan if you consider only one gene: Both of you might have the same blood typewhile your next-door neighbor might not, for example. Nevertheless, it is somewhat more likely that your neighbor will have the same blood type as you, since the frequency of blood types varies according to nationality. If you look over the whole genome—about 20,000 genes—with a match with your neighbor being somewhat more likely for every single gene, the chance of the overall match with someone Japanese being closer than the match with your neighbor becomes vanishingly small. Think of it this way: When you make a bet at the casino, the odds favor the house, although not overwhelmingly so. You might win that first bet—it's not that unlikely. But what is the chance that you'll win most of the time over the course of a year—win the majority out of thousands of bets, with the odds against you on
every one? The probability of that happening is vanishingly small, which is why the house always wins in the long run.
As a practical matter, if you can distinguish between the members of two populations by looking at them, genetic analysis will be able to do so as well. And sometimes it will be able to make such distinctions when you can't tell by looking at them. The question as to whether the Ashkenazim are genetically distinct is now settled: We know from the data that they are. But that by itself it not enough to prove our thesis that they are more intelligent than the rest of us, or even that they are significantly different in any other way—not by a long shot. Being measurably different is not necessarily the same as being significantly different, and knowing that systematic genetic differences exist does not automatically tell us what their consequences are.
However, this initial set of data could have disproved our thesis. If the genetic evidence had indicated that the Ashkenazi
Jews could not constitute a genetically distinct group—if there had been significant continuing gene flow—then we would have to concede that our proposed mechanism (natural selection) could not have occurred. But the initial dataset did not disprove our thesis. So what does the genetic evidence say about Ashke- nazi intelligence?
The 10,000 Year Explosion Page 18