Another one of my favorite chapters in Racehorse Breeding Theories was the last chapter, Chapter 16, “Evaluating Breeding Theories–Looking for the Real Patterns Underpinning Tesio’s Greatness,” by Ross Staaden, B.V.Sc., Ph.D.
The Tesio part of that chapter was great. A lot of BS has been written about Tesio. Sometimes I think that almost as much BS has been written about Tesio as has been written about Jesus Christ. This chapter exposed a lot of the BS written about Tesio for exactly that.
But what I liked MOST about that chapter was Staaden’s dozen rules for evaluating breeding theories. I would like to quote them all, but I will settle for one paragraph from his eighth rule, which is: The further back into the pedigree a theory has to go, the more likely it is rubbish.
“With every generation, the influence of a particular ancestor is halved. More importantly, in every mating, it is a different half, a different subset of the great ancestor’s genes, a different group of chromosomes handed down. A sire passes different traits to different offspring, and especially to different grand-offspring. His sons, for example, have at least half of his genes for every trait, but their offspring may get none of the grandsire’s genes for a particular trait.”
“With every generation, the influence of a particular ancestor is halved.” Staaden does not state WHY this is so. Probably because everyone knows the reason and assumes it to be DOGMA.
The reason why the influence of a particular ancestor is halved with every generation is ONLY because there are TWICE as many ancestors in each generation: two in the first generation, four in the second generation, eight in the third generation, etc.
And that is the ONLY thing a geneticist means when he states that the influence of a particular ancestor is halved with very generation. It is halved because each generation has TWICE as many ancestors. Therefore, the probability that a particular gene is handed down from ancestor to foal halves with each succeeding generation.
Clear as MUD so far????? I wish to point out two things at this point in the discussion. The first is that the geneticist’s definition of “influence” has NOTHING to do with ACTUAL RACING PERFORMANCE. It is merely an expression of the probability of inheriting a specific gene from an ancestor. It makes no statement whatsoever as to whether that specific gene will help or hurt racing performance (or have no effect whatsoever on racing performance).
Now let us consider the remainder of that paragraph:
“More importantly, in every mating, it is a different half, a different subset of the great ancestor’s genes, a different group of chromosomes handed down. A sire passes different traits to different offspring, and especially to different grand-offspring. His sons, for example, have at least half of his genes for every trait, but their offspring may get none of the grandsire’s genes for a particular trait.”
Genetic inheritance in the Thoroughbred is a crapshoot (as I stated in my last post), and the paragraph above details some of the reasons why. Ancestors beyond the first generation do not transmit racing ability with any degree of regularity or reliability.
I discussed some of the reasons for that in my last few posts. Here is another one. A common misconception exists that full siblings are 100% related. NOT TRUE. On average they are 50% related (have half of their genes in common). They could be 100% related, although the chances of that are very slim. They could be 0% related, although the chances of that are equally slim.
The second thing I wish to point out is that the geneticist’s definition of “influence” (probability of a gene being inherited) does not take into account the fact that some generations are more important than others. Some generations are more important than others specifically if you are trying to estimate the probable racing class of a foal from its pedigree.
Even more specifically, the first generation is more important than the second generation, the second generation is more important than the third generation, etc. The fourth and fifth generations are items of idle curiosity only. And you can DEFINITELY FORGET anything beyond the fifth generation when it comes to estimating the probable racing class of a foal from its pedigree.
This can be easily demonstrated. The best demonstration can be found in Chapter 2 of Racehorse Breeding Theories, pages 29-30. I will elaborate somewhat on that demonstration.
Mr. Prospector was by Raise a Native out of Gold Digger, by Nashua. As everyone knows, Mr. Prospector was one of the best sires of the 20th century.
Mr. Prospector had four full brothers who also went to stud. They were Search for Gold, Red Ryder, Kentucky Gold, and Vaal Reef. I list them in order of merit, though the former two were only mediocre and the latter two were considerably worse than that.
So imagine that you are looking at the second generation of a pedigree, and the first two names you see on top are Raise a Native and Gold Digger. You are probably very pleased, thinking this foal is by Mr. Prospector, who has “the right stuff” and transmits it with some regularity.
The problem is that you are allowed to look at the second generation ONLY. You are NOT allowed to look at the first generation. You are trying to decide whether to buy this foal. Thinking that the foal is probably by Mr. Prospector, you decide to do so and pay $500,000 for it.
After you buy the foal, then you are allowed to look at its first generation. Imagine your consternation after you have paid $500,000 for this foal and are allowed to look at its first generation and you see that it is NOT by Mr. Prospector, but by Search for Gold, Red Ryder, Kentucky Gold, or Vaal Reef. You have just paid about $495,000 too much for this foal (or maybe $499,000, depending on which of the four sires it is).
The point is that the names Raise a Native and Gold Digger in the second generation are not nearly as important as the name Mr. Prospector in the first generation. If you think the second generation is just as important as the first generation, I have for sale just for you some wonderful oceanfront property in Arizona.
Let us imagine another scenario. This time around you are allowed to look at the fifth generation ONLY and not at any of the closer generations. Among the 32 ancestors in the fifth generation you see four pairs of Raise a Native–Gold Digger. You jump to the conclusion that the foal in question must be 4x4x4x4 to Mr. Prospector. Imagine your consternation once you have bought the foal and are allowed to see the rest of its pedigree that it is NOT 4x4x4x4 to Mr. Prospector. Four of its eight sires in the fourth generation are Search for Gold, Red Ryder, Kentucky Gold, and Vaal Reef.
Not that a foal inbred 4x4x4x4 to Mr. Prospector is necessarily a GOOD proposition. But it is a BETTER proposition than a foal with Search for Gold, Red Ryder, Kentucky Gold, and Vaal Reef as four of its eight sires in the fourth generation. The important point here is that the fourth generation is more important than the fifth generation. And the first generation is VASTLY more important than the fourth or fifth generations.
So we have two facts here. The first is that “influence” (as defined by geneticists) decreases by half with each succeeding generation ONLY because there are twice as many ancestors in each succeeding generation. Not too many people will argue with that.
The second fact is that when seeking to evaluate a foal from its pedigree and predict its probable racing class, for all practical purposes the first generation is the most important generation and is more important than the second generation, which is more important than the third generation, etc. If you want to argue with that fact . . . you probably think that the Pope shits in the woods too.
The next question is: What logical conclusion(s) can be drawn from these two facts???? I am usually not much of a practitioner of the Socratic Method, but in this case I am. I am calling upon readers to take the next step for themselves and to answer the question above.