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This paper is an attempt to pinpoint a number of genetic markers needed to establish the top 8% (IQ > 130) level of intelligence, using an extended family across several generations. Idiopathic intelligence flagged by gustatory sensation has been asserted for some time (Mascie Taylor, 1994) and at least twenty four genes spread over three chromosomes respond to the bitter taste provided by many poisons of differing molecular structures.
In the early 1990s, several researchers showed that the ability to taste phenylthiourea was linked to IQ and in 1994 the author added the ability to roll one’s tongue to the framework. In 2000 multiple ability to taste a number of varied chemicals was bonded to a rising tested intelligence.
The author believed that this groundwork of increasing sensory perception might have been the neurological foundation of “intelligent behaviour” in the ancestral mammal because the cerebrum arose as an outgrowth from the primitive “smell brain”. Here ten markers have been used and tested in pairs. The intelligence test employed has been one attempted by this family for several decades to ensure continuity and has a standard deviation of 20. Adjustments were made for age and the subjects ranged from sixteen to sixty years of age. All were approached in their own homes or called to the home of the author.
Stankov (2001) has done an excellent survey of olfaction and intelligence, and stimulated the work reported in this paper.
Testing has been spread over months or years to avoid fatigue or making the subjects defensive, so that several generations have been brought up to expect measurement. The only resistance has been occasionally offered by spouses brought in from outside Pembrokeshire.
Tasting and smelling were kept as simple as possible. A few grains on the tongue or a sniff from a specimen bottle was enough. Most of the markers have a vile taste, so as little as possible was used. Wet or dry ear-wax was reported as “runny ears”, or not. Tongue tube or rolled tongue is self-explanatory.
Currently 658 people have been available for testing, but a number are still children and others have died before completing all the tests. The numbers actually employed are shown in Table 1. Gender was balanced.
For some time it has been recognised that tasting uracil is generally the reciprocal of tasting PTC.
The ability to taste 6np2tu (or not) has been located on chromosome 5 and wet or dry ear wax controlled by a gene on chromosome 16.
Within this series there is a correlation between uracil and 4HMP (d.f. 77, correlation 0.4173; p=0.001), but this may be particular to the family or a sampling artefact due to low numbers.
Table 1 shows the results of tests on the various samples of family members. The first row shows that 346 family members were tested for tube tongue. Of these 192 tested positive and their mean IQ was 127.2. The other 154 tested negative and their mean IQ was 119.1. So the average IQ of those testing positive was 8.1 points higher than the average IQ of those testing negative. The other rows in the table show similar analyses for the other traits tested.
The last column is a crude estimate of the probability that the difference between the mean IQs of those testing positive and those testing negative is due to chance. It can be seen that only for tube tongue and PTC is the difference significant at the 5% level – ie less than 5% probability of positive and negative testers having same mean IQ and observed difference being due to chance. But, for these two traits, the difference is highly significant.
Table 2 shows the effect of testing positive for two of these traits compared with testing negative for two of them. 45 different permutations were tested but only those shown in the table produced mean IQ differences between those testing double positive and those testing double negative that were significant at the 5% level. As might be expected, all but one of these involved either PTC or tongue tube.
Mice live a complex life of genetic recognition by odour, and humans can recall deep, old, poignant memories on the drift of a fleeting breeze, even if the sense of smell is now considered secondary. Galton (1883) emphasised the role for sensory processing in intellectual functioning, however that may be defined, but gustatory systems seem to have been treated with timidity even though the mammal originally used this as the dominating sense.
In this study, taste has been the major agent and its application has been kept at a simple level of positive perception or nothing. In some cases the negative reactions were so few that the author wondered if a pathological state was involved. Six tastes, two smells, a physiological difference and a common muscular distortion were employed to illustrate the theme.
The traits were analysed into forty-two pairings and thirty-six of these showed a relatively high IQ for the double positive. A low score for the double negative has been demonstrated elsewhere. (James 2000)
The gene or genes controlling wet/dry ear wax have been located on chromosome 16. This is the chromosome that also carries a gene concerned with short-term memory, an important component of intelligence. Variation in 6-n-propyl-2thiouracil tasting is linked to chromosome 5 – which one survey linked to schizophrenia. However, schizophrenia has been linked to so many chromosomes that this observation is probably not significant.
In an attempt to pick out the most heavily loaded alleles concerned with intelligence, the table showed two that, whatever they were combined with, were positively associated with enhanced IQ. Wet ear wax and 4hydroxy-2mercaptan-6propyl pyrimidine produced means of 129.3 and 132.2 respectively. The overall mean of the family is 122 so that this is quite a jump in operational efficiency. (Tongue tube positive provides the same mean as ear wax.)
It must be emphasised that these data have been collected from one slightly isolated extended family which is increasingly taking in foreign spouses, but other surveys in distant areas may show surprising cline effects. We may find different verbal or spatial components. FOXP2 (a major gene involved in the development of language, differing from the chimpanzee equivalent by only two amino acids within the last 200,000 years – see Wellcome News, April 2002) is on Chromosome 7 and Plomin has found an intelligence booster on Chromosome 6. Like immunity (another learning system), intellectual control may spin a web across the genome with “fall back” operational support if things go wrong in one section. Thus a child of bright parents may prove mediocre if one set of genes does not match.
From this survey. tongue tube and PTC only have a clear
association with elevated IQ and tongue tube may rest upon two genes (James
Nevertheless the other common markers have been eliminated from this exciting search.
1. ‘Inheritance of intelligence in a Pembrokeshire family’; James P (1996), The Linnean 12, 2:20-28
2. ‘Intelligent Behaviour and Possible association with minor inherited traits’; James P F (2000), Social Biology and Human Affairs 65, 2:20-30
3. ‘Receptors and transduction in taste’; Bernd Lindemann, Nature 13 September 2002
4. ‘An amino-acid taste receptor’; G Nelson et al, Nature Vol 416, March 2001, pp 199 et seq
5. ‘Association between some polymorphic markers and variation in IQ and its components in Otmoor Village’; Mascie-Taylor C G N et al (1994), Behaviour Genetics 7: 47-51
6. ‘Tongue tube/IQ’; James P F, Galton Institute Newsletter, December 1994
7. ‘Genetics and General Cognitive Ability (g)’; Robert Plomin and Frank M Spinath, Trends in Cognitive Sciences, Vol 6, No 4, April 2002
8. ‘What the Nose Knows: Olfaction and Cognitive Abilities’; Stankov L et al, Intelligence 29 (2003) 337-361
9. ‘Sugar Sweetness and Pleasantness: Evidence for different Psychological Laws’; Howard R Moskowitz et al (3 May 1974) Science Vol 184: 4136 pp 583-585
10. ‘Genetic Relatedness assessment through individual odour similarities in Mice’; G Heth et al, 595-603 Biological Journal of the Linnean Society April 2003 Vol 78 Number 4
11. ‘Nature Insight: Molecular Sensing”; Nature 13 Sept 2001
12. ‘The Human Genome’; Nature 15 February 2001
13. Enquiries into Human Faculty and its Development; Galton F (1883) New York Macmillan
14. Group Tests of Intelligence; P B Ballard, University of London Press (1957)
15. ‘Neural Mechanisms of General Fluid Intelligence’; J R Gray et al, Nature Neuroscience 6 316 March 2003