Japanese scientists report that variations in individual genes seem to determine the color of the grapes. Their study speculates that black grapes have evolved white grapes due to a variant that suppresses the production of pigments called anthocyanins. It also shows that red grapes are not an intermediate step in the evolution process. Instead, it is actually the second mutation that restores the production of anthocyanins, which grow red grapes. Shozo Kobayashi found that one of the genes involved in the production of anthocyanins was only expressed in certain species of red grapes but did not appear in white grapes. In the white grape variety, a series of invasive DANs called "reverse nests" insert themselves into the gene to prevent the grapes from producing pigment. A further examination of the red grapes revealed traces of the molecules left by the retrograde insert before leaving the gene. Researchers speculate that, if not all, this variant gene has spread to the vast majority of white grape-growing plants around the world.