The evolution of racial differences in intelligence

Source : Mankind Quarterly, Fall/Winter91, Vol. 32 Issue 1/2, p99, 23p (condensed here)

Author : Richard Lynn

Hominids first evolved in tropical and subtropical latitudes, most probably reaching sapiens status in the highlands of East Africa. From this ancestral population some groups migrated north into Eurasia and evolved there into the Caucasoids and Mongoloids. Colonizing temperate and cold environments, they encountered the cognitively demanding problems of survival in cold winters. These problems consisted principally of securing a food supply by hunting large animals and of keeping warm in winter by making fires, clothing and shelters. Survival in these difficult conditions acted as a selection pressure favoring enhanced intelligence and explains why the Caucasoids and the Mongoloids are the races which have evolved the highest intelligence.

Caucasoid peoples of North America, Britain, Continental Europe and Australasia obtain mean IQs of around 100. Mongoloid peoples in East Asia and in North America typically obtain mean IQs a little higher in the range of 101-108. They are also characterized by strong visuospatial abilities and weaker verbal abilities. The same pattern is found in the Amerindians, but the level of their intelligence is lower with a mean of about 90.

Negroid peoples are generally considered to have a mean IQ of approximately 85, but this is only true of those in the United States and Britain. African Negroids have a mean IQ in the region of 70. American and British Negroids are more properly considered as Negroid --Caucasoid hybrids, and hybridization has evidently raised their intelligence levels to about midway between the two parent races. The South East Asian races consisting of Micronesians, Melanesians, Polynesians, Maoris and Australian Aborigines typically have mean IQs in the range of 80-90.

These differences in intelligence test performance are corroborated by racial differences in the building of civilization. It is reinforced by the results of differences in reaction times between the three major races of Negroids, Caucasoids and Mongoloids. Reaction times provide a measure of the neurological efficiency of the brain in the analysis and processing of simple stimuli, and reaction times show the same progression of ability from Negroids to Caucasoids to Mongoloids as has been shown by intelligence tests. These results confirm the conclusion that the racial differences are neurologically and genetically based. If this is the case, the racial differences must have evolved in accordance with the general principles of natural selection which determine evolutionary development..

The general principles governing the evolution of intelligence have been established by Jerison (1973). He has shown that from time to time populations have moved into new niches which have entailed increased cognitive demands for survival. When this has occurred the populations have responded by evolving larger brains in relation to body size, i.e. Iarger "encephalisation quotients". Larger brains have the capacity for greater intelligence and have enabled the populations to deal with the cognitive demands of the new niche.

The single origin theory states that the evolution from Homo erectus to Homo sapiens probably took place in the highlands of East Africa, and that some Homo sapiens populations then migrated into Eurasia and replaced the Homo erectus and Neanderthal peoples (Stringer and Andrews, 1988). According to this theory Homo sapiens populations were established in southwest Asia, in the region of present day Israel and Lebanon, by about 92,000 years ago and from there further groups migrated throughout the world. By 60-40,000 years ago they were established in northeast Asia (Jorde, 1985), and by 40-30,000 years ago they were in Europe and Australasia (Mellars and Stringer, 1989), evolving and adapting all the time.

The central thesis of our argument is that either through a multi-regional or single origin process the Homo sapiens peoples in Eurasia had to adapt to the problems of survival in cold temperate and sub-arctic environments, while those in Africa evolved in tropical, sub-tropical or warm temperate environments. The thesis to be advanced is that the Caucasoid and Mongoloid peoples who evolved in Eurasia came to occupy a new niche which exerted selection pressure for improved intelligence to deal with the problems of survival in the cold northern latitudes. The thesis is an application to the problem of racial differences in intelligence in man of Jerison's principle that the cognitive demands of a new niche have been the selection pressure for increases in intelligence throughout evolutionary history.

Primates evolved rapidly following the extinction of the dinosaurs. They lived on plant foods and those which evolved into monkeys and apes remained largely plant eaters, supplemented to some extent with insects. A few primates, most notably baboons and chimpanzees, sometimes kill small mammals for food, but meat has never become more than a small part of their diet (Strum, 1981).

The conclusion that people in tropical and subtropical latitudes were never greatly reliant for their food supply on the hunting of animals for meat is supported by observations on contemporary hunter gatherers. Many non-cultivating populations living in tropical and subtropical environments subsist largely on plant foods of which numerous species are available throughout the year (Lee, 1968; Tooby and de yore, 1987). The ready availability of plant foods throughout the year, together with insects and eggs, meant that people in tropical and subtropical Africa never had to rely on meat for their food supply and did not come under strong selection pressure to develop the cognitive skills required to hunt large animals.

The life style of present day !Kung bushmen in the Kalahali desert provides a useful insight into the relative ease of securing food supplies for hunter gatherer peoples in tropical latitudes. As described by Lee (1968), women go gathering plant foods about one day in three, and men go on hunting expeditions for about one week in three. This is sufficient to provide food for the whole group, including infants, children and the old. The rest of the time can be spent relaxing about the camp. For these peoples the problems of obtaining food supplies are neither time consuming nor cognitively demanding.

The only hominid species to overcome the problems of survival in the cold temperate climates of Eurasia were Homo erectus and Homo sapiens. The problems of over wintering would have been considerable even during warm periods such as the present, but during the periodic glaciations these problems would have been much more formidable. Most of the last 80,000 years has been colder than today. During the main Wurm glaciation of approximately 24-10,000 years ago winter temperatures in Europe and north east Asia fell by 5-15Celcius. The terrain became cold grasslands and tundra with only a few trees in sheltered river valleys and the environment was broadly similar to that of present day Alaska (Nilsson, 1983). Survival in these conditions would have called for greater intelligence than was required in the tropical and sub-tropical climates of sub-Saharan Africa.

The problems of survival in the northern latitudes of Eurasia would have resided in the cold winters and consisted principally of obtaining food and keeping warm. Unlike the tropics and subtropics, plant foods were seasonal and not available for many months during the winter and spring. People therefore became wholly reliant on hunting large herbivores such as mammoth, horse and reindeer to secure their food supply.

The effective hunting of large herbivores would have presented cognitive problems. Large herbivores can run fast and are virtually impossible to catch simply by chasing after them. It is particularly difficult to hunt them in open grasslands such as were present in Northern Eurasia, where there is good visibility for several thousand yards and the herbivores have ample warning of approaching predators. Hunting in open grasslands is more difficult than hunting in the woodlands of the tropics and sub tropics where there is plenty of cover for hunters to hide in. The only way of hunting animals in open grasslands was to make use of natural traps into which the animals could be driven. One of the commonest traps was the narrow ravine where some of the beasts would stumble and could be speared by members of the group waiting in ambush. In addition, the herbivores could be surrounded and driven over cliffs, into bogs or into the loops of rivers (Geist, 1978; Mellars, 1989).

For effective hunting of large herbivores people would have needed to manufacture a variety of tools from stone, wood and bone for making spearheads and for cutting. When these peoples had killed a large herbivore they would have had to skin and butcher it into pieces of a size that could be carried back to the base camp. For this it was necessary to manufacture a variety of sophisticated cutting and skinning tools.

The second principal set of problems encountered in the northern latitudes would have centered round keeping warm. People had to solve the problems of making fires, clothes and shelters. The problems of starting fires and keeping them burning would have been considerably more difficult in Eurasia than in Africa. In addition clothing and shelters were unnecessary in sub-Saharan Africa but were made in Europe during the main Wurm glaciation. Needles were manufactured from bone for sewing together animal skins and shelters were constructed from large bones and skins (Geist, 1978; Mellars, 1989).

The manufacture of sophisticated tools and making fires, clothing and shelters would have been cognitively demanding. Those groups which could not succeed would have died out, leaving those with alleles for higher intelligence as the survivors. Through this process the Caucasoid and Mongoloid peoples of Eurasia would have evolved higher average intelligence levels than the Negroids exposed to a less cognitively demanding environment in sub-Saharan Africa.

Survival in the cold winters of Eurasia would surely have required an increase in all the three major components of intelligence, namely general, verbal and visuospatial ability. Hunting and tool making would have been undertaken principally by males and this would be why it has virtually always been found that the visuospatial abilities are stronger in males than in females (Lynn and Petersen, 1986).

General, verbal and visuospatial abilities are all higher in the Caucasoid peoples as compared with Negroids. The magnitude of the Caucasoid advantage is about the same for all three abilities, namely about 30 IQ points for the Negroid-Caucasoid comparison and about 15 IQ points for the difference between Caucasoids and Negroid-Caucasoid hybrids in the United States and Britain.

It is apparent that the intelligence of the Mongoloids evolved somewhat differently. The Mongoloid peoples have slightly higher general intelligence than the Caucasoids, markedly higher visuospatial abilities and somewhat weaker verbal abilities, and we must now consider how this pattern of abilities could have evolved. The reason that Mongoloids have more highly developed general intelligence than Caucasoids can be attributed to the colder winters they experienced and hence the stronger selection pressure for increased intelligence. Mid-winter temperatures in north east Asia are colder than in Europe, particularly inland in the area around Lake Baikal where the classical Mongoloids evolved.

It was in response to this severe cold that the Mongoloids evolved their distinctive morphological cold adaptations to reduce heat loss, such as the shortening of the limbs, the flattening of the nose into the face, the thick black hair, the reduction of the beard in males because moist exhaled air in very low temperatures freezes on the beard and then freezes the face; and the epicanthic fold, a thickening and extension of the eyelid near the nose which serves to reduce reflected glare from snow and ice (Coon, 1962; Krantz, 1980). These morphological adaptions are most pronounced among the classical Mongoloids, particularly the Buriats and the Tungus who lived in the coldest region of inland eastern Eurasia. They are less pronounced among the southern Chinese and among the Ainu, the original inhabitants of Japan for whom the climate was more maritime and therefore less severe.

The south east Asian races would have spent some time in temperate Asian environments before they migrated eastward. This would have exerted some selection pressure for enhanced intelligence, but the duration of their exposure to cold winters would have been relatively short as compared with the experience of the Caucasoids and Mongoloids.

The Indian Caucasoids had a longer period of exposure to the cold winters of northern India, which were significantly colder during the main Wurm glaciation than they are today. This explains why Indians invariably obtain higher intelligence levels than Negroids, whether they are in India or South Africa,,where their mean IQs are around 85 or in Britain where their mean IQs are around 95, as shown in our review.

It is well known that the Amerindians originated from peoples who crossed the Bering Straits and made their way southward into the Americas. The studies reviewed previously showed that the profile of intelligence of the Amerindians is similar to that of the Mongoloids in so far as they have strong visuospatial and weak verbal abilities. The whole profile is lower than that of Mongoloids by around 1 standard deviation, so that their general intelligence stands at around 90 as compared with a Mongoloid mean of around 105

The Amerindians escaped exposure to the severe cold of the main Wurm glaciation. Once they had crossed the Bering Straits and made their way down into the Americas they would have found life a good deal easier than their ancestors had been accustomed to in north east Asia. They would have found a number of herbivorous mammals such as mammoth, horse antelope, sloth, armadillo and bison who were quite unused to being hunted by man. So they would have found large numbers of inexperienced herbivores who were easy to catch and, in addition, as they moved southward they would have found that plant foods were more readily available. They ceased to rely exclusively on hunting for their food and adopted the easier life style of the hunter gatherer in which plant foods played a significant part in their diets (MacNeish, 1976; Hayden, 1981).

Thus in the new environment of the Americas survival would have been much easier. The Amerindians would have retained their elevated level of general intelligence, as compared with the Negroids, which their ancestors would have gained in north east Asia during the early Wurm glaciations. They would also have retained their well developed visuospatial abilities. These enabled them to continue as effective hunters and there would have been no selection pressure to evolve any different pattern of abilities.

Throughout the course the evolution new species have from time to time evolved with larger brains or, more strictly, higher encephalisation quotients, to accommodate greater intelligence. These increases in brain size have occurred to deal with the problems of survival in new cognitively demanding riches. It has been argued that one of these occasions took place when hominids migrated from tropical and subtropical Africa into the temperate and cold environments of Eurasia. These migrants; who evolved into the Caucasoid and Mongoloid peoples, have invariably been found to have higher average intelligence levels than populations descended from those who remained in tropical and subtropical latitudes. The question to which we turn now is whether the Caucasoids and Mongoloids evolved larger brains to accommodate their greater intelligence, as had happened on previous occasions in the history of evolution.

In the last century and the early decades of the present century there were a number of claims that Caucasoids had larger average brain sizes than Negroids but in recent years it has come to be widely claimed that these studies have been discredited (Gould, 1981). Nevertheless, the figures given by Gould for brain size for the major races indicate that Mongoloid and Caucasoid brain sizes are larger than those of Amerindians, and these in turn are larger than those of Negroids.

Finally, Beals, Smith and Dodd (1984) collected results from approximately 20,000 crania and classified them into geographical and climatic zones. They found the largest brain size in Mongoloids, followed in descending order by Caucasoids, Amerindians, south east Asians and Negroids.

Although brain size relative to body size correlates with intelligence across species, there has been a marked reluctance among anthropologists to admit that brain size is related to intelligence in man. In spite of these assertions, there is in fact quite solid evidence for a positive association between brain size and intelligence in Homo sapiens.

The argument is now complete. Brain size is positively correlated with intelligence in man, and the races show consistent differences in both brain size and intelligence. These differences appear to have arisen because the Caucasoids and the Mongoloids colonized a new and cognitively demanding niche when they migrated into the temperate and cold environments of Europe and Asia. In these harsh environments the less intelligent failed to survive, and this left the Caucasoids and the Mongoloids as the two most intelligent races and the only two races that have made any significant contribution to the development of civilization. The evolution of racial differences in intelligence in man has followed the same principle that has operated throughout evolutionary history, namely adaptation to a new and cognitively demanding niche.

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