>You might want to ask _why_ it is "very common and repeating". There is
>strong circumstantial evidence that it is "very common and repeating" for
>the same reason that most female honeybees are sterile workers; it is
>to the long-term advantage of the genome to express a phenotype that is
>not optimized for reproductive success but that enhances the reproductive
>success of its close relatives. There's no "just so" about this sort of
>phenotypic oddity; it's an evolutionary adaptation that is or was useful
>to us.
>A good starting point if you want to read about this is "The Extended
>Phenotype" by Richard Dawkins. If nothing else, it may make you question
>the many facile over-simplifications of Darwinian theory that we are
>constantly bombarded with because they support various ideological
>positions.
Totally. Spike has already brought this up.