[two individual entities d1 and d2 stand in a shares_ancestor_with relation if and only if there exists some a such that d1 derived_by_descent_from a and d2 derived_by_descent_from a.]
[Count of number of days intervening between the start of the stage and the time of fertilization according to a reference model. Note that the first day of development has the value of 0 for this property.]
[Count of number of months intervening between the start of the stage and the time of birth according to a reference model. Note that the first month of post-birth development has the value of 0 for this property, and the period during which the child is one month old has the value 1.]