[8][9] However, in normal individuals no effect on mental ability or behavior has yet been demonstrated in either this or another similarly studied microcephaly gene, ASPM.

John Derbyshire wrote that as a result of the findings, "our cherished national dream of a well-mixed and harmonious meritocracy [...] may be unattainable.

Bruce Lahn maintains that the science of the studies is sound, and freely admits that a direct link between these particular genes and either cognition or intelligence has not been clearly established.

[23] A later 2010 study by Rimol et al.[12] demonstrated a link between brain size and structure and two microcephaly genes, MCPH1 (only in females) and CDK5RAP2 (only in males).

In contrast to previous studies, which only considered small numbers of exonic single nucleotide polymorphisms (SNPs) and did not investigate sex-specific effects, this study used microarray technology to genotype a range of SNPs associated with all four MCPH genes, including upstream and downstream regulatory elements, and allowed for separate effects for males and females.