We estimate the degree of relatedness between every pair of individuals in a study to identify unexpected relatedness. Three identity-by-descent (IBD) coefficients (Z0, Z1 and Z2), the probabilities of sharing 0, 1 or 2 alleles that are identical by descent, are estimated using a method of moments procedure implemented with PLINK software [Purcell, et al. 2007] and compared with their expectations and evolutionary variance (see Supporting Information). Some pedigree errors can be corrected by consulting original records, while others are corrected based on the inferred genetic relationships.
