Societies used to know these things - it's the basis for hereditary rule and class systems. Marx and others have persuaded many people that it's not true, but it is. We all see it, but it's currently fashionable (and often legally required) to deny it. We need to get (back) to systems that take this into account - true meritocracy,(reply>), @Braveheart that's true - meritocracy is an improvement over hereditary aristocracy, but you would see upper class children accede into the upper class. Not all, but mostly. A generation ago we used to talk about "being from a good family" - you rarely hear that today.