At Our Wits' End, page 6
Of course, this doesn’t mean that we would expect chimpanzees to eventually become as clever as us and then enslave us, like in Planet of the Apes. Growing a large brain, which is associated with intelligence, would involve directing energy away from growing big muscles, for example. In the unstable, dangerous, but relatively intellectually undemanding environment of chimpanzees—where basic needs like warmth or food are met—this would be damaging. So, there would be no selection for super-intelligent chimps—instead an optimum level of intelligence would be maintained.
Hunter-Gatherers
Moving on from chimpanzees, this combination of social, sexual, and natural selection for intelligence and health is very obvious in the least developed human social organisations: hunter-gatherers. These peoples mainly live off foraging from the local environment and, occasionally, meat brought into the community by male hunters. In some cases, they have developed very primitive forms of agriculture, tending a small garden in territory they regard as their own. But, in general, territory is held collectively by the band.[11]
These groups are unstable, often splitting into separate groups over minor arguments, and they have very high levels of child mortality. Around 50% of children die from accidents or poor resistance to disease. In addition, in many of these tribes, such as the Yanomamö of Venezuela, unhealthy or simply unwanted infants will be killed by their mothers or allowed to starve. There is also a tendency for stepfathers, who may even have killed the father in a fight and taken his wife, to kill young stepchildren.[12] For all of these reasons, in the groups from which modern humans evolved there is selection in favour of the appropriate level of strength, aggression, and good genetic health.
But we can also see how there would be selection for intelligence. Partner intelligence does not seem to be considered significant for short-term relationships. In the latter case, physical qualities which betoken good genetic health are what is most important. However, when looking for somebody with whom to have a long-term relationship—where children might result, for example—females are more interested in males’ social status (and by extension his intelligence) than vice versa. This is likely because a male of high status will, in general, be more able, and more willing, to invest resources in the female and her offspring.[13] And she will benefit from this investment when she is pregnant and has young children, meaning that she and the children will be more likely to survive. Accordingly, the female (and her offspring) will be more likely to pass on their genes. For this reason, there are sex differences in the qualities that we find attractive in partners. Although there are all kinds of shades of grey in between, overall it really is true that men go for looks and women go for money and status or the potential to achieve these.[14] Men go for looks because they have less to lose from the sexual encounter. Thus, unless they intend to invest in the family, their best strategy is to have sex with as many healthy and fertile—and thus good-looking and young—women as possible.14
In order to understand this selection for intelligence more, let’s focus on the Yanomamö or, as other tribes term them, ‘the fierce people’. They are a group of about 35,000 people living in up to 250 separate villages on the Brazil–Venezuela border. They are extremely violent, with men settling disputes by smashing each other on top of the head with logs until one of them loses consciousness or dies. This leaves the heads of the males as a mass of scars which they show off as evidence of their fortitude. The hierarchy is clearly based around access to females. The ‘headman’ will have about three wives and roughly eight children, while lower ranking men will have one or even no wives and a smaller number of children.[15] This means that only the strongest, healthiest, and most intelligent men will make a significant impact on the gene pool. As Darwin put it, in describing these kinds of tribes:
‘The strongest and most vigorous men, those who could best defend and hunt for their families, and, in later times, the chiefs or headmen, would have succeeded in leaving a greater number of offspring than would the weaker, poorer and lower members of the same tribes. The chiefs of nearly every tribe throughout the world succeed in obtaining more than one wife.’[16]
This can also be seen among the Bushmen of the Kalahari Desert, who live in small bands and migrate from one watering hole to another. One study of this group found that infant mortality was 45%, and that 62% of adult males produced no children at all. There is an excess of females, due to male deaths on hunting trips, and, as such, the headman will have an excess of wives.[17] Reviews of hunter-gatherers all agree that most of these peoples follow status-based polygamous mating systems.[18]
We are not aware of any intelligence test which proves that the headman would be cleverer than his subordinates, but there’s certainly good circumstantial evidence that this is the case. One of the means by which men in these tribes attract women is by being good at hunting. They can use the (rare) meat they obtain on hunting trips as presents for those they like, or as food for their children. The anthropologist Janet Siskind explains in her ethnography of the Sharanahua of Peru that: ‘Prestige accrues to the generous hunter. Prestige is not a vague goal at Marcos, it brings a definite reward, the possibility of gaining women as lovers and/or wives. The successful hunter is usually the winner in the competition for women.’[19] Such abilities would also impress the males whom they would hope to lead. But, clearly, skill at hunting would involve not just good physical health but also intelligence. The ability to hit the target or make the best weapons would be predicted by spatial intelligence and lightning reaction times. Building and maintaining the weapons would require high impulse control and planning for the future. Reaching the top of the hierarchy would require the social skill involved in making alliances and understanding the best time to pose a challenge, while good verbal intelligence would be necessary to persuade rival males or outdo them in tests of wit. So, we would expect the headmen to have relatively high intelligence by the standards of the tribe, and it would be these very people who would be disproportionately passing on their genes.
This view is backed up by qualitative evidence from anthropologists, who have lived with these hunter-gatherers. Napoleon Chagnon is an American anthropologist who did long-term ethnographic fieldwork with the Yanomamö in the 1960s. In his ethnography, he writes: ‘Kaobawa, on the other hand, has the special status of being the group’s headman ... Kaobawa thinks for the others in the village, many of whom are not able to perceive some of the less obvious implications of situations. In political matters, he is the most astute man in the group, but he so diplomatically exercises his influence that others are not offended.’[20] Kaobawa is strongly implied to be the most intelligent man in the village. American evolutionary psychologist David Buss has summarized that, ‘In tribal societies, the headman or leaders are inevitably among the most intelligent in the group.’[21]
We must also think in terms of group selection—i.e. where selection operates on groups of individuals. Chagnon found that the Yanomamö and similar hunter-gatherer groups are in a constant state of war against rival villages. This being the case, if the level of aggression were roughly similar then we would expect the healthier and more intelligent of the two villages to triumph and slaughter the males from the other village. This would be an obvious example of ‘group selection’. This is because the more intelligent village would develop superior war strategies, produce better weapons, and engage in better planning.
Pastoralists
Pastoralists are nomadic peoples who keep a variety of domesticated animals such as goats and chickens. They frequently migrate from place to place in order to find fresh pastures for their herds. They are a more complex form of society than that of hunter-gatherers; they reflect a greater degree of specialisation, and there are clearer differences in social status within these groups. These differences strongly impact whether or not people have children and we have already noted that social status is partly predicted by intelligence.
The first pastoralists appeared in Neolithic times, around 10,000 years ago, in the so-called ‘Fertile Crescent’ on the shores of the Mediterranean. Pastoralists can sustain larger populations than hunter-gatherers because they can produce a surplus of food in order to feed these larger populations. A modern example of such a people is the Rendille camel herders of Northern Kenya. In this society, there is very strong selection both for physical prowess and intelligence. At the age of around 11, a boy undergoes a bloody rite of passage, in public, in order to transition from being a boy to being a warrior. He must sit perfectly still as he is circumcised. If he betrays the slightest emotion then he will shame his family and himself. At best he will be an outcast, who cannot marry, and, at worst, he will be killed by his furious and humiliated relatives. Clearly, this would select for physical prowess and thus good health. Once the male graduates to warrior status, he can get married, but only once he can pay the ‘bride price’, which is paid in camels. Only about 50% of Rendille males ever accrue enough camels to be able to pay the bride price, and so, in general, only the more socioeconomically successful males will father children at all.[22] We have already seen that socioeconomic status is predicted by intelligence, so this system would have the indirect effect of preventing those of both low intelligence and poor health from having children.
A number of these pastoralist peoples have become agriculturalists. This means that there is even greater surplus and so an even larger population, though there will tend to be a greater concentration on one particular kind of crop. There are hundreds of studies of these kinds of people and almost all concur that there are polygamous mating systems through which the wealthier males achieve the highest fertility. In addition, there are arduous rites of passage which weed out the males who are low in physical health. Accordingly, there is selection for intelligence and physical vigour. We would, in fact, expect selection for intelligence to be stronger among agriculturalists than among hunter-gatherers. To pursue agriculture successfully, you require far higher impulse control and a much stronger degree of orientation towards the future, such that you can achieve a surplus, ready for times of famine. As you are settled, and cannot move with the seasons, you have to keep warm and thus manufacture appropriate clothes and more complex and versatile dwelling structures. In order to marry, you must be highly successful in agriculture, being able to pay the bride price, and this would require far higher intelligence—as reflected by the heightened ability to plan and practise self-discipline—than would hunting ability.[23]
Early Nation States
As agriculture improved further, such a large food surplus could be achieved that there was no need for everybody to even work in agriculture. Increasing numbers of people were able to pursue specialisms that had nothing to do with agriculture directly or simply employ others to work on their land while they lived a life of ease. As such, around 5,000 years ago we begin to see the development of city states, especially around the Fertile Crescent. A clear social class system develops. At the top, there are the kings, the nobility, and the leading religious and military figures, then there are the wealthy farmers, merchants, and craftsmen, then there are labourers and poorer farmers, and at the very bottom are slaves who are literally owned by members of the higher classes. These societies were generally polygamous and there is sound evidence that members of the higher social classes enjoyed many wives and extremely high fertility.[24]
We need look no further than the Old Testament in search of evidence for this. King Solomon (c.990–931 BC) ran a harem of around a thousand sexual partners:
‘King Solomon, however, loved many foreign women besides Pharaoh’s daughter—Moabites, Ammonites, Edomites, Sidonians and Hittites. They were from nations about which the Lord had told the Israelites, “You must not intermarry with them, because they will surely turn your hearts after their gods.” Nevertheless, Solomon held fast to them in love. He had seven hundred wives of royal birth and three hundred concubines, and his wives led him astray.’ (I Kings, 11)
Other Old Testament kings also had very high numbers of wives, though nothing to match Solomon. King Rehoboam of Judah, for example, had 18 wives and 60 concubines. Among the Incas of Peru there were legal regulations on the extent of polygamy. Emperors could have as many wives and concubines as they desired while military officers were permitted between 30 and 15, depending on their rank.[25] In China, emperors maintained harems of hundreds of women who would be rotated according to their time in the menstrual cycle. As such, they would have hundreds of children.[26] It is recorded that the Moroccan emperor Moulay Ishmael the Bloodthirsty (1634–1727) fathered 888 children. These were produced by hundreds of concubines and 9 wives, including ‘Mrs Shaw, an Irish woman’ who was taken as a slave by Barbary pirates during a raid on her native land.[27]
As the societies become more complex, the social differences become greater, which leads to another form of selection both for intelligence and health. The upper classes simply had considerably better access to nutritious food than the lower classes, who would eat a poor diet, be close to starvation, and live in very unhealthy conditions. Many studies have compared skeletons from higher and lower class graves and demonstrated that the upper class skeletons displayed evidence of better nutrition and were also taller, because they had been able to reach their maximum genotypic height due to good nutrition. Among the Maya in Central America, upper class skeletons were, on average, 7cm taller than lower class skeletons.[28] This association between social class and height can also be seen in Early Modern England. The average sailor on the English ship The Mary Rose, which sank in 1545, was 5ft 7 inches tall.[29] However, Henry VIII was 6ft 3 inches,[30] Edward IV, Henry’s grandfather, was 6ft 3-and-a-half inches,[31] and Mary, Queen of Scots was almost 6ft.[32] These significant differences in nutrition would have had a direct effect on the ability to conceive, on the likelihood that a child would survive into adulthood, and on life expectancy. They would have meant that there was a form of social selection in favour of the wealthy and, therefore, in favour of the more intelligent. And this would have been in addition to the impact of sexual selection, with upper class men having greater access to females. Thus, it can be argued that intelligence would be more strongly selected for in these early states than was the case among agriculturalists or pastoralists, as a consequence of the development of a social class system with significant differences in living standards.
The Christian World
In some respects, the adoption of Christianity by the Roman Empire may be regarded as damaging to selection for intelligence, and we will explore possible reasons for the fall of the Roman Empire in Chapter Eleven. Christianity began as a religion of the poor and dispossessed and, thus, it made sense to espouse monogamy, as this was in the interests of the poor. Under a system of polygamy, as we have seen, the wealthier men will monopolise the females, leaving low status men unable to pass on their genes. As such, the adoption of monogamy by the Roman Catholic Church would have decreased the intensity of selection for intelligence.
Secondly, clerical celibacy was imposed by the Council of Carthage around the year 400, though it had been strongly encouraged as early as 306. Those who were already priests were banned from getting married, or having sex with their wives if they were already married.[33] Priests would have been among the most educated, and thus the most intelligent, people in the society at the time and so imposing celibacy upon them would have weakened selection for intelligence. Some priests did sire illegitimate children anyway, as we will explore shortly.
Thirdly, the Church prohibited abortion, which would have led to the births of many—often illegitimate—children from unwanted pregnancies.[34] These would be more likely to be the children of those of relatively low intelligence who had acted in the moment and not considered the future consequences. However, this may be balanced by the fact that the Church also banned contraception, to the extent that Europe simply lost the knowledge of it. The more intelligent would have been more efficient in using this than the less intelligent. It is widely accepted in the medical literature that those of low intelligence are at most inefficient users of contraception.[35] The more intelligent may even have been more inclined to use it because, due to being wealthier, it is probable that they would have experienced lower levels of infant mortality.[36]
However, in spite of this, there is evidence that the selection for wealth continued in the form of de facto polygamy. Despite the official monogamy, the nobility would generally have mistresses in addition to their wives; often servant girls working in their households. William the Conqueror, who invaded England in 1066, was the illegitimate son of Robert, Duke of Normandy, and succeeded his father to the Dukedom. Until the Reformation, it was so socially acceptable for the upper class to have illegitimate children by mistresses that these ‘noble bastards’ or ‘royal bastards’ would be acknowledged by their father, take their father’s surname, be raised in his household, and be provided for by him, often lavishly. Historians Katharine Carlton and Tim Thornton examined 876 wills from northern England made over the period 1450 to 1640. Of these, 11% had specifically marked illegitimate beneficiaries. Of these 96 wills, 8 belonged to nobles, 27 to knights, 23 to esquires, and 38 to gentlemen—the latter three being the ranks of the gentry, the English ‘lower nobility’, in descending order.[37] The historian Stephen Staves has noted that upper class men in Early Modern England would generally have ‘roughly as many illegitimate children as legitimate ones’.[38]
