Good reason exists to doubt whether genes advantage black Americans at sport as Jon Engine claims -- the phenomena of the birthday or age cut-off effect. There is nothing genetic about being born in August rather than September but it can profoundly change the odds on becoming a professional footballer or tennis player [as well as being treated for mental sub normality or dyslexia]. The cut-off effect shows that big population differences need not be genetic since they can arise from apparently small environmental ones. The mere existence of different numbers of blacks and white in a sport thus says nothing by itself about genetic advantage [that requires evidence of correlations between differences at the individual level between anatomy and physiological sport related traits and actual sporting success] -- dramatic population differences could equally be due to apparently insignificant environment factors such as date of birth. For example, in the English FA premier league over twice as many players, 285 are born in the three months Sept-Nov as the earlier three Jun-Aug, 136.

Gene wise they are the same. In a similar way, the Dutch tennis year starts from the beginning of the calendar year: half its young league players between 12 and 16 are born in the three months January to March (Dud link, 1994; Edwards, 1994). The same effect with different months (month cut-offs vary with sports) has been found in cricket with fast bowlers, tennis players and hockey players. If having a birthday in the wrong month can have such dramatic effects, what might be the effect of having a dark skin and the constant prejudice that means you are academically born dumb but bodily athletic? Such effects could be large due to similar mechanisms to those that create the birthday effect. This arises due to a self-amplifying advantage or disadvantage in the opportunity to learn a skill. Individuals in a group cannot all succeed or all failure.

Some are winnowed as better. These tend to those that are eldest in an age group -- those born in September against August because they are slightly more mature in body and motor skills. This initial advantage in turn accumulates and self-sustains in later years even when the initial maturity difference has ceased. The same effect occurs for reading and learning problems and could cause avoidable educational failure (Bell & Daniels, 1990; Williams, Davies, Evans & Ferguson, 1970).

At the start of infant school, a child born on August 31 will be in with kids born the previous September 1 -- at their age nearly a quarter of a life older. Worse, since vocabulary-based language skills only start developing fully somewhere between two and three: a July or August child will be competing against peers who have been speaking nearly twice as long. For the average child this might not matter, but for one with a problem it might educationally sink them. Less developed and delayed, they will be different, unable to keep up with peers and at risk of a cycle of self-reinforcing decline. When learning in groups, unable to keep up with others, they will stop learning and end up at the bottom of the class.

Any problems will magnify as they fall further and further behind. It can be seen in statistics: July and August children have a 50% greater chance than other children of being diagnosed or treated as having learning problems. To give some numbers of ESN (educational subnormal) children in special schools from one study (Williams, 1964: table 2). (Note the expected average should be within one child of 22 per month). Month number June 21 July 27 August 37 Sept 10 Oct 19 Nov 17 In Sweden which starts the school year in January, it is children born in the autumn that have the problem. The performance of black Americans on intellectual tests is known to relate to apparently insignificant environmental factors such as the number of blacks in their mother's class.

Moreover, blacks are keenly aware of the prevailing belief that they are not very smart -- something that is known to produce anxiety and related poorer performance -- see Steele, C. M. , & Aronson, J. [1995]. Stereotype threat and the intellectual test performance of African Americans. Journal of Personality and Social Psychology, 69, 797-811.

The existence of such an anxiety factors raises the question whether beliefs about sporting achievement might shape black American performance in sports though enhanced confidence and ambition. Though small, such an effect -- as with month age -- could self amplify itself resulting in profound statistic effects as the population level. Expectations, after all, about what an individual can do and cannot do have profound effects upon their determination and persistence in such things as training and so shape in a self-fulfilling way judgements made about what they can do -- and with that the opportunities to further develop them. Beliefs about self-efficacy as Albert Bandura has shown strongly effect what we achieve see Bandura, A.

(1982). Self-efficacy mechanism in human agency. American Psychologist, 37, 122-147. This is not to deny the possibility of a superior genetic ability in black Americans in sport: only that citing population statistics is without meaning. The real science must involve analysis at the individual level in terms of anatomy and physiological traits, sporting success, and degrees of African ancestry [a factor that varies markedly between black Americans]..