On the principle underlying the tabular method to compute coancestry.

The tabular method to compute coancestry between two individuals is based on the principle that coancestry may be computed as the average coancestry between one individual and the parents of the other, on the condition that the former individual is not a direct descendent of the latter. It follows that coancestry also may be computed as the average of the four coancestries between the parents of the two individuals, on the condition that each individual is not a direct descendent of the other. The requirement for these conditions is explained.