Horse running through field

Affinity Schleminity!

By Roger Lyons

It seems the old eugenic notion of “purity of blood” just won’t go away. For the last couple of years one website in particular has been featuring it as the one and only theory of nicks, and with a zeal that is–well, I’ve always wanted to use this word, but didn’t have a chance until now–mythomaniacal. I’m referring to the obsession with explaining nicks in terms of the “genetic affinities” that are supposedly exploited by crossing “close genetic relatives.”

The term “genetic affinity” might not seem as crass as the term “blood affinity,” but they are close etymological relatives nonetheless, their pedigree tracing to the idea that all good things spring from pure blood. This figure of speech originally served the purpose of invidious social class comparison. Needless to say, it’s un-American. It’s also un-French. It’s even un-German. It’s English.

To the unreflective pedigree analyst, it’s all but irresistible. You take the ancestry of an individual stakes winner, and then you find individual, similarly bred ancestors of both sire and dam (don’t worry, you’ll find them if you go back far enough), and you proclaim, “That’s why this horse is a stakes winner.” This game has no rules, and it’s open to all. It works for any ancestry, and, if you repeat it enough times, then some people will be persuaded.

But here’s my main beef with that approach. It violates the dictum that tests of a theory must, in principle, have equal opportunity to confirm and to disconfirm the theory. Within an anecdotal framework the theory of genetic affinity can be confirmed till the cows come home, but such tests could not possibly disconfirm it, precisely because close genetic relationships are ubiquitous in thoroughbred pedigree.

In my last blog post I took a statistical approach to deconstructing the supposed genetic affinity between Halo and Prince John. I might have chosen any combination of the many ancestors that have been trotted out in tandem over the years as examples of “close genetic relatives.” I concluded that there’s no genetic affinity between Halo and Prince John, but the argument goes farther than that. There’s no such thing as a genetic affinity. Period.

One needn’t appeal to the supernatural or to The Catalogue of Unacceptable Ideas in order to account for nicks. I’m convinced that the relation between types and traits is all we need. Let me illustrate.

During his career, the stallion Woodman sired foals out of 54 mares that descended in some way from Better Self (by Bimelech, a son of La Troienne, and out of Bee Mac, by War Admiral), and only one of those mares produced a superior runner by him, a strike rate far below his norm.

Another son of Mr. Prospector, Gone West, sired foals out of 61 mares in some descent of Better Self, and nine of those mares produced a superior runner by him, a strike rate well above his norm.

Now, here are the premises of a simple theory based on the relation of types and traits.

1. Better Self, rarely occurring in pedigrees closer than the fourth or fifth generation of mares, is so prepotent in regard to a certain trait or set of traits that individuals in any given descent routinely express that trait or set of traits.

2. Any given stallion tends to throw offspring within a certain range of type.

3. From a performance standpoint, the trait or set of traits so persistently conferred by Better Self may accord with, or even complement, the range of type of a given stallion’s offspring (Gone West), but it may affect the offspring of another stallion (Woodman) in an extremely unfavorable way.

It’s a simple theory. No hocus pocus. No need for the mysteries of genetic affinity. This theory probably isn’t exactly right, at least not comprehensively so, but its great advantage is that it’s subject to both confirmation and disconfirmation by way of tests combining statistical observation and biomechanical analysis.

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