If we trace a ball dropping from one level to the next in the quincunx, we see that the displacement at the next level inherits the sum total of variations bestowed upon it by all the pegs along the way, which indicates that generation 2 does not inherit the luck of generation 1. However, luck is a transitory occurrence.

In Figure (a) (Galton’s conception), success is transmitted across generations, and luck variations accumulate indefinitely. This is perhaps natural if “success” is equated to wealth or eminence.

However, for the inheritance of physical characteristics like stature, we must replace Galton’s model with that in Figure (b). Here only the genetic component, shown here as talent, is passed down from one generation to the next. Luck affects each generation independently, in such a way that the chance factors in one generation have no way of affecting later generations, either directly or indirectly.

Both of these models are compatible with the bell-shaped distribution of heights. But the first model is not compatible with the stability of the distribution of heights (or success). The second model, on the other hand, managed to explain the stability of success from one generation to the next by explaining the stability of the genetic endowment of the population (talent).