Ancestral Duplication Explained
Ancestral Duplication identifies every ancestor appearing more than once in a pedigree and scores how much influence each duplication actually carries, across both the sire and dam sides.
Naming a duplication is easy. Any pedigree chart shows you that a horse appears twice. The harder question, and the one this panel answers, is how much that duplication weighs and where the weight sits.
Why position matters more than presence
Two pedigrees can both be inbred to the same ancestor and behave completely differently. A duplication close up carries far more genetic weight than one several generations back, and a duplication loaded onto one side of the pedigree behaves differently to one spread across both.
That is the reasoning behind scoring rather than listing. A raw count of duplications treats a close-up 3x3 and a distant 6x6 as equivalent, which they plainly are not.
For the underlying concepts, see inbreeding, linebreeding and outcrossing.
What the panel shows
Total Duplicates. The overall duplication load in the pedigree. This is the density measure: how much of the pedigree is repeated material rather than distinct ancestors.
Parental Balance. How evenly the duplicated ancestors are distributed between the sire and dam sides. Balanced duplication tends to produce more consistent outcomes than duplication concentrated on one side, which is why this is reported as a figure in its own right rather than left for you to infer.
Male-Line Duplicates and Female-Line Duplicates. Duplication running through male pathways and through female pathways, counted separately. The distinction matters because the two reinforce different things. Male-line concentration strengthens sireline traits. Female-line concentration strengthens maternal traits and family consistency.
Top Male Duplicates and Top Female Duplicates. The individual ancestors carrying the most duplication weight, named, on each side. This is usually where you look first, because it tells you what the pedigree is actually built around.
X-Line Duplicates. Duplication assessed along the X-chromosome inheritance pathway.
Generation depth
The analysis can be run at several depths, from five generations out to eight, and a separate view assesses the dam's own pedigree.
Depth changes the picture considerably. Almost any two thoroughbreds share ancestors if you look far enough back, so a very deep view will find duplication everywhere and tell you little. A shallow view may miss a pattern that is genuinely doing work. Start at five generations, which is the depth most breeding theory is framed around, and go deeper only when you are testing something specific.
How to read what you find
Look at the top duplicates first. The named ancestors carrying most weight tell you what the pedigree is concentrating. If that ancestor is one you want reinforced, the duplication is working for you. If it is a horse known for transmitting a fault you are trying to breed away from, the same duplication is a liability.
Then check the balance. Heavy duplication concentrated on one side is a different proposition to the same load spread evenly, and Parental Balance is the fastest way to see which you have.
Then check the pathways. Whether the reinforcement is arriving through male or female lines shapes what it is likely to strengthen.
Do not treat density as a score. More duplication is not better, and neither is less. Dense linebreeding can reinforce elite traits and it concentrates risk at the same time. The right level depends on the mare, the traits sought, and what the duplicated ancestor transmits.
Where it sits
Ancestral Duplication appears as a panel within the Impact Profile, alongside the cross analysis. The two answer different questions about the same pedigree. Impact Analysis asks whether particular combinations have produced stakes winners. Ancestral Duplication asks how the pedigree is structured.
The Breeding Theory Finder builds on this, testing whether the duplication structure satisfies named breeding theories such as Rasmussen and Sex Balance.
Because it runs on hypothetical matings as readily as on named horses, the duplication structure of a proposed cross can be examined before a nomination is booked.