"People who received two Cs from their parents, about a quarter of the population, scored on average 1.3 points higher than the next group - half of the populat

"People who received two Cs from their parents, about a quarter of the population, scored on average 1.3 points higher than the next group - half of the population with only one C in this section of the gene. The last quarter of people, with no Cs, scored another 1.3 points lower." I'm sure it's a significant step in cognitive research finding a gene that correlates to differences in intelligence but is a 2.6 point spread that big a deal?