How much genes account for IQ?

Recently I watched videos about genes on Youtube. Robert Plomin describes that genes account for nearly 50% of an IQ. People usually predict around 41%. The enviornmental effect was smaller than we think. Furthermore, as people get older, genes account more for IQ. These findings are very counterintuitive. As people get older, they choose a more gene-friendly environment or they shape their environment to be gene-friendly. This hypothesis explains counterintuitive findings. If you are interested in this topic, watch this video.