Discussions of race and intelligence, as well as claims of genetic differences in intelligence along racial lines, have appeared in both popular science and academic research since the inception of IQ testing in the early 20th century. The concept of "race" is a social construct, and "intelligence" has no agreed-upon definition; the validity of IQ tests as a metric for general intelligence is itself disputed. In particular, there is no scientific evidence that the average IQ scores of different racial or ethnic population groups can be attributed to any claimed genetic differences between those groups.