It's been proven that IQ tests are created with unintended bias toward the creators. A quick example is that white British children score higher on pen and paper tests whereas Sub-Saharan African children score higher on wire tests. The difference is only that one group is more used to working with pen and paper and other with wire as a cultural difference rather than a true intelligence gap.
Also,
https://en.wikipedia.org/wiki/Flynn_effectLots of good information there.