The explanation is simple. Domestication implies neoteny, as observed in animals. Civilization effectively domesticates humans and makes them more neotenous, hence why Asians look young so long: they've been civilized continuously for longer than most white people. Looking young (neoteny) is an aspect of feminine beauty, so Asians also look more feminine, hence white men love Asian women and white women have zero attraction to Asian men. Black people, on the other hand, have not been civilized, so they are less domesticated, less neotenous, and look more masculine. So white women go for them.
