- is the coefficient of inbreeding of the individual;
- is the number of common ancestors of the individual's parents;
- indexes the common ancestors;
- is the number of generations from the father to common ancestor ;
- is the number of generations from the mother to common ancestor ; and
- is the coefficient of inbreeding of common ancestor .
Equation (1) is hard to compute and has been criticised by more recent writers. The coefficient of inbreeding of the children of unrelated but inbred parents is set to zero. Therefore, at Familypedia we use the following coefficient:
- is the Familypedia coefficient of inbreeding for ; and
- is the Wright coefficient of inbreeding of the parents as defined by Equation (1) for .
Equation (2) is easy to compute as it only uses information about the parents and their relationship. The Wright coefficients can be seen from Table 1.
Table 1. Wright coefficient of inbreeding for selected cases
|Relationship between parents||Coefficient of inbreeding|
|Double first cousins||0.125000000|
|First cousins once removed||0.031250000|
|First cousins twice removed||0.015625000|
|Second cousins once removed||0.007812500|
|Second cousins twice removed||0.003906250|
|Third cousins once removed||0.001953125|