Do you know what you don't know?

By Carol Beuchat PhD

True or False?

 

As breeders use inbreeding to improve consistency in their litters, they are also increasing their ability to improve traits through selective breeding.

 

When people try to make sense of something, they dig out whatever information they have in their head and apply it. If what's in your head is all derived from personal experience, that's the information you use. If what's in your head is from education, you use that together with experience.

Let's take a simple example. If you flip a fair coin, you will get heads half the time and tails half the time. But if you flip a coin 10 times you are unlikely to get 5 heads and 5 tails. We don't see this as a violation of some grand design because we think we understand chance. Yet if you start flipping a coin and get 97 heads in a row, your brain might be screaming at you to predict the next toss will be tails. But if you have had a course in probability or statistics, you will know that even after 97 heads in a row, you are not more likely to get tails than on any other toss.

When I posed the question at the top in the ICB Breeding for the Future Facebook group, I was surprised to see that many people thought the statement was true and just as many thought it was false. Also, many of the explanations used words or phrases like "believe", "think", "this makes sense", "it's logical that...", and so on, and there were also examples from personal experience to support an answer. But the people who chose true and those that chose false can't both be right.

The whole point of science is to figure out how the world works through observation and experimentation, and one thing we all know (or should) is that there are many things we might think we "know" from limited personal experience that turn out not to be true. The process of science multiplies "experience" many times to provide more reliable information about something. A trained scientist should be keenly aware of the difference between what they think might be true about something based on experience, a hunch, or a few observations (and they might call it a hypothesis), and what is true (or accepted to be true) based on rigorous science. But for the layperson, this difference is not always so obvious. And it's easy to "confirm" what you might want to believe to be true through something called "confirmation bias".

Without the factual information about something, we all tend to fall back on experience, logic, opinions, and beliefs, and we are even more convinced that we understand something when it is confirmed by others. But many times we really don't know enough about something to know how likely we are to actually be correct.

Henry David Thoreau said something that I really like because it's the perspective I bring to the way I think about science: 

To know that we know what we know, and that we do not know what we do not know, that is true knowledge.

Half of knowledge is knowing the things that are known. But the other half of knowledge is knowing that there is much you don't know, and that you can't even know what those things are.

So back to the statement at the top. What's the answer? Is it true or false?

If money is the currency of commerce (because it lets you buy things), then allelic diversity is the currency of selection. You can't change a trait (improve or otherwise) if there is no variation among individuals in the relevant alleles. Inbreeding has the advantage of improving consistency in a litter because it reduces the variation in alleles. But at the same time, there is less variation in the alleles that you need for selection. As inbreeding in a population increases, your ability to change a trait (for better or worse) using selective breeding decreases.
 
Breeders understand the advantages of inbreeding for consistency, but many fail to see that as their dogs become more and more similar genetically, they are less and less able to change traits through selection. You will hear people say things like "once you lose your fronts, they are hard to get back," or "temperament problems are hard to correct". These are statements about highly polygenic traits; they are influenced by MANY genes, and if the genes for those traits are homozygous in a population, no amount of selective breeding will improve them because you have no variation to select from.

If you understand this concept, you will understand that there is a critical balance you need to achieve in order to have good type in your dogs as well as the ability to improve particular traits. Livestock breeders try to keep inbreeding below 5-10%. Nature tends to keep the level of inbreeding in healthy wildlife populations much lower, usually less than 1%. Most purebred dog breeds have an average level of inbreeding greater than 10%, and many are in the range of 25% and even 50% or more (!!!). You might have good consistency, but it's really hard to produce something much better than what you have with these high levels of inbreeding. Because of this, relentless inbreeding is a dead end.

There's another fact that is handy to know in thinking about this problem. As inbreeding increases, so does something called "linkage disequilibrium" (LD). Linkage disequilibrium is the tendency for alleles to be inherited in groups instead of independently and randomly. So you might be trying to eliminate something in your line by selecting against it, but some of the genes you don’t want are in a block of genes with one you are selecting for. You can either keep both, or lose both, but selection will not improve one while eliminating the other. Inbreeding increases the size of these blocks of genes that move around together. Populations with higher genetic diversity have lower LD, so they are able to respond faster and with more precision to selection than inbred populations. Yes, there is more variation (less consistency), but the opportunity for genetic gain (improving a trait through selection) is much greater. You can buy exactly what you want if you have lots of money that gives you choice.

The statement at the top is false for two simple reasons. Inbreeding reduces your ability to improve traits because of a) lower allelic diversity and b) higher linkage disequilibrium.

The people who understood the principles of genetics that the question addresses were able to answer it easily and with a simple statement of that rule. They didn't offer opinions or logic or personal anecdotes (some of which actually "proved" the wrong answer), they didn't wander around in the weeds of ambiguity, or get mired in what looked like contradictions expressed as "what about this, but what about that?" They relied on a simple principle of genetics to address the question. They probably didn't know this from their personal experience, because it would take breeding many, many litters and good knowledge of other principles of genetics to come to this conclusion. They knew this through education, which also provided the evidence needed for them to understand why it is true.
 
I keep pounding away at the importance of education. Without it, you have no way to know whether the things you "know" are actually true or false. Many people chose "True" in answer to the question, and they probably think they are correct. If they don't know the science, they will continue to believe that.
 
Every breeding you do is an (expensive) experiment. If the rules you breed by are actually incorrect, it's going to be hard to produce what you want. And you'll also use what you think you know to come up with reasons why things didn't work as expected. Knowing this little bit of information about the relationship between inbreeding and the allelic diversity needed for selection, you should have a different perspective on the process you use to make breeding decisions. In fact, your perspective will change even more if you know more of the rules.
 
I posed this question because I was curious to see how people would respond. I really didn't expect to see so many votes for both True AND False, or the number of explanations offered that didn't really support the answer. What is clear is that many people did not know the simple fact that would have made this question easy, and worse - they don't know that they don't know. No doubt, many people are basing breeding decisions on "information" that is simply untrue. How effective and efficient can a breeding program be if it is based on incorrect information?
 
What would you say to these statements: true or false? After you decide, follow the links.
 
Hybrid vigor does not occur in dogs.
"I know what's in my lines"
Breed only the best to the best and spay/neuter the rest.
Recessive mutations should be removed from the gene pool.
There is quality in a singleton puppy.
The dam is more important than the sire.
Inbreeding does not increase health problems in purebred dogs.
We have to protect genetic purity of breeds with closed stud books.
 
You will hear all of these statements in discussions about dog breeding. They are all false because they violate simple principles of genetics that are true whether you believe them or not. How can you breed the best possible dogs if you don’t know the rules of the game?
 
There is no better way to spend some of the time and money you invest in dogs than in your own education. This is why ICB teaches courses. Take them. The COI Bootcamp course is free and you can take it any time. Take the two courses ICB offers in population genetics. Invest in yourself and become a smarter breeder.

Know the things that are true, and know that you don't know what you don't know.

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