[A.J.Armitage]

If I may volunteer an answer; It's a statistical inevitability. Aberrations of this order are bound to occur within a sampling of any billion or so people.

From what I see, it's more than a few aberrations. But anyway, why are there bound to be some?

[Barnacle]

But anyway, why are there bound to be some?

Because with in any sample group you will have an average, or typical example that generally defines that group, as depicted in the illustration below.

Although the bulk population of that group will be concentrated near the mean center, and will be generally representative, smaller populations that deviate from the norm can be found to the left and right of the center. This principle is applicable to most natural occurrences, whether the subject is the height of adult males or the number of miles you can get from tires.