For the past century raw scores on IQ tests have been rising; this score increase is known as the "Flynn effect," named after Jim Flynn. In the United States, the increase was continuous and approximately linear from the earliest years of testing to about 1998 when the gains stopped and some tests even showed decreasing test scores. For example, in the United States the average scores of blacks on some IQ tests in 1995 were the same as the scores of whites in 1945.[61] As one pair of academics phrased it, "the typical African American today probably has a slightly higher IQ than the grandparents of today's average white American."[62]
https://en.wikipedia.org/wiki/Race_and_intelligence
IQ is a culture thing not a brain thing