Felix Volkbein
07-31-2014, 05:04 AM
In his book on eugenics, Richard Lynn speculates that such a ceiling probably exists:
However, although the average running speed of thoroughbreds has increased, there has been no improvement in the fastest running speeds, which have remained the same for about a century. Records are not broken virtually every year, as they are in Olympic events. The fastest horse ever was Sovereign, who lived between the two World Wars. The reason the fastest running times have not improved is that all the genes (alleles) for the fastest running speeds must have been present in the 1791 thoroughbred population. These have been increased by selective breeding, while at the same time the alleles that reduce speed have been reduced. It is very unlikely that new mutant genes for faster speeds have appeared. Because running speeds are determined by a number of characteristics, each determined by a number of genes, the chances of a horse inheriting all the best genes for running speed are very low; and it is a matter of chance when these, together with optimum environmental factors, appear in a particular horse.
The experience of the breeding of thoroughbreds over the past two centuries serves as a useful model for what could be anticipated if eugenic measures were introduced for humans. In the case of intelligence, there would not be any increase in the highest intelligence hitherto achieved. The highest IQs ever recorded are about 200, the intelligence level estimated for Blaise Pascal (Cox, 1926) and Francis Galton (Terman, 1917a). An IQ of 200 means that a child of a particular age is at the intellectual level of the average child of twice this age (e.g., a four-year-old is at the level of the average eight-year old). We should not expect that a eugenic program would increase the highest achievable IQ to 300 or 400. This is because all the right genes and the most favorable environmental conditions have already appeared from time to time and produced people like Pascal and Galton. What a eugenic program would accomplish would be the reduction or elimination of the genes for low intelligence. The average intelligence level of the population would be improved, just as the average running speed of thoroughbreds has been improved; but there would be no increase of the highest IQs, just as there has been no improvement in the running speeds of the fastest thoroughbreds.
However, although the average running speed of thoroughbreds has increased, there has been no improvement in the fastest running speeds, which have remained the same for about a century. Records are not broken virtually every year, as they are in Olympic events. The fastest horse ever was Sovereign, who lived between the two World Wars. The reason the fastest running times have not improved is that all the genes (alleles) for the fastest running speeds must have been present in the 1791 thoroughbred population. These have been increased by selective breeding, while at the same time the alleles that reduce speed have been reduced. It is very unlikely that new mutant genes for faster speeds have appeared. Because running speeds are determined by a number of characteristics, each determined by a number of genes, the chances of a horse inheriting all the best genes for running speed are very low; and it is a matter of chance when these, together with optimum environmental factors, appear in a particular horse.
The experience of the breeding of thoroughbreds over the past two centuries serves as a useful model for what could be anticipated if eugenic measures were introduced for humans. In the case of intelligence, there would not be any increase in the highest intelligence hitherto achieved. The highest IQs ever recorded are about 200, the intelligence level estimated for Blaise Pascal (Cox, 1926) and Francis Galton (Terman, 1917a). An IQ of 200 means that a child of a particular age is at the intellectual level of the average child of twice this age (e.g., a four-year-old is at the level of the average eight-year old). We should not expect that a eugenic program would increase the highest achievable IQ to 300 or 400. This is because all the right genes and the most favorable environmental conditions have already appeared from time to time and produced people like Pascal and Galton. What a eugenic program would accomplish would be the reduction or elimination of the genes for low intelligence. The average intelligence level of the population would be improved, just as the average running speed of thoroughbreds has been improved; but there would be no increase of the highest IQs, just as there has been no improvement in the running speeds of the fastest thoroughbreds.