Every ancestor contributes a proportion of a dog's expected genetic makeup — parents 50%, grandparents 25%, halving with each generation. When an ancestor appears multiple times through linebreeding, their contribution increases. Ancestor Contribution calculates each ancestor's total proportional contribution and derives a single diversity index: fe.
Where pi is each ancestor's proportional genetic contribution as a decimal. Even contributions → small sum of squares → high fe. Concentrated contributions → large squared terms → low fe.
With a full 10-generation pedigree and no inbreeding, fe grows closer to the number of unique ancestors. When linebreeding concentrates contributions, fe drops.
The Inbreeding Analysis page ranks top contributing ancestors by blood percentage. Parents will typically be at the top (~50% each). The interesting information is in non-parent ancestors — grandparents and beyond with unusually high contributions, suggesting linebreeding or popular sire effects. Click "Show all" for the complete list.
Dog → Genealogy → Inbreeding Analysis
Ancestor Contribution appears alongside the PCI block, showing fe, unique ancestors, diversity ratio, parental contributions, and the ranked top ancestors list.