The Mean Gene?

By D. Caroline Coile, PhD.

Reprinted with permission from Dog World.
Copyright 2005 D. Caroline Coile. All rights reserved. Reproduction of this article in whole or in part is strictly prohibited. To subscribe to Dog World, go to www.dogchannel.com.

While certain genes and enzyme, can affect canine behavior, proper training and socialization during puppyhood greatly influences a dog's future personality and temperament.

Imagine being told you had to get rid of your dog. Not because of anything he did, but simply because of his breed and genes.

It's happened in many communities to owners of dogs labeled inherently vicious, banned by breed-specific legislation. Different breeds have been targeted, but the reason is always the same: the assumption that aggression is hereditary in dogs of certain types or breeds. In most cases, legislators' evidence comes not from scientific studies, but from media reports and fatal attack statistics. The problem is that media reports often inaccurately label dogs as belonging to certain breeds or types. And although between 38 to 50 percent of fatalities are ascribed to "pit bulls" and Rottweilers, more than 35 other breeds have also been responsible for fatalities, according to the National Canine Research Foundation.

Dog advocates justly argue that breed-specific legislation is ineffective and unfair. It has the additional drawback of making genetic studies dealing with canine aggression a political hot bed. The most basic of questions used to determine if a trait is genetically influenced is whether it responds to selection -a question that at first glance seems easily answered by looking at differences in aggressive tendencies among breeds bred for different levels of aggression. If only it were that simple.

First, there's the problem of defining aggression. Researchers have subdivided canine aggression into as many as 13 different types. One of the most wellknown subdivisions uses eight categories: fear-elicited, dominance, possessiveness, protectiveness, intra-specific, punishment-elicited, pain-elicited, and predation. Different breeds appear more likely to display different types of aggression. For example, Doberman Pinschers, Toy Poodles, Lhasa Apsos and English
Springer Spaniels are more likely to show dominance aggression, whereas German Shepherd Dogs are more likely to show protective aggression.

But as anyone who has tried to battle breed-specific legislation knows, reporting breeds as more or less prone to any kind of aggression is no easy task. First there's the problem of breed identity. Second there's the problem of breed popularity. Golden Retrievers have a fairly high rate of dog bite reports; but then there are more Golden Retrievers compared to most other breeds.

Breeds can instead be ranked as a percentage according to registration statistics, but not all dogs are registered and breed popularity can be regional a problem when looking at regional statistics of dog bites. To adjust for regional variation, yet another method is to compare the number in each breed presented to a veterinary school for aggression versus the number presented for medical reasons. This, too, skews the statistics because some breeds will be more likely to have medical conditions that can be treated at veterinary teaching hospitals. Nonetheless, some breeds appear near the top of the list for aggression no matter what statistical analysis is used.

Why should that surprise us? One of the main tenets of selective dog breeding is that continued selection through generations has given us breeds that are as behaviorally suited to a job as they are physically. Some jobs require higher degrees of assertiveness or aggression. In addition, breeders know too well the effects bottlenecks, founder effects, and genetic drifts can have on any small isolated population. Just as they can account for undesirable physical traits, so can they account for undesirable behavioral traits.

But most scientists agree there's no such thing as a "mean gene" although one discovery comes tantalizingly close. Monkeys and rats with low or absent levels of the enzyme monoamine oxidase have a greater tendency to behave aggressively as compared to those with normal levels. MAO regulates the breakdown of the neurotransmitters serotonin, norepinephrine, and dopamine, all important in behavior. Although a rare circumstance in humans, in one family several members lacked the gene for producing MAO they included a man who raped his sister and stabbed a mental institution warden with a pitchfork; another who tried to run over his boss; and two others who were arsonists. No doubt, however, such family members exist with normal levels of MAO as well.

It's not always a yes or no issue with MAO. A promoter region near the MAO gene can switch the gene on and off, controlling the amount of MAO. But humans - and we would argue, dogs - are more than beings simply controlled by their genes. In a long-term study, low MAO men from abusive childhoods tended to become violent adults, whereas those from nurturing childhoods did not. Men with normal MAO levels did not tend to become violent no matter what their upbringing. Thus, as with all things behavioral, it is the interaction between genes and the environment that is the major determinant.

What about MAO in dogs? No data yet exists comparing MAO levels in different breeds, or in aggressive versus non-aggressive individuals. If it did, and if certain lines were abnormally low, breeders might use that as a breeding guide. More likely, they would remember the lesson from the human study and make sure the dogs were raised in a manner that would buffer the effects of their genes - something all breeders should do anyway.

Besides, MAO is just one of several genetically influenced chemicals that may influence behavior, at least of mice and men. Far less is known about specific genes that influence behavior in dogs. In 1999 the first such gene was identified, a D4 dopamine receptor gene called D4DR - a gene that has been related to novelty seeking behavior in humans. In comparing two breeds generally acknowledged to differ in scores of reactivity, the Shiba Inu and Golden Retriever, the more reactive Shiba was found to have more of the long-D allele than the generally less-reactive Golden.

As more canine genes are identified, more will doubtless be associated with behavior and even aggression. Meanwhile, what does this mean for dog breeders? All dogs are aggressive to some extent, and in some circumstances. The acceptable degree and desirable circumstances will differ from owner to owner and according to the dog's function.

Part of our problem today is what some authors have termed the "Disneyfication" of dogs, in which dogs are considered "furkids" and expected to act with Lassie-like, or at least Gandhi-like, benevolence. Yet there's a truth all breeders must cope with: dogs are dogs, and dogs will act aggressively at times. That's one reason humans selected them as their best friends. Perhaps Plato put it best 2000 years ago: "The disposition of noble dogs is to be gentle with people they know, and the opposite with those they don't know ......"

B. Caroline Coile, Ph.D., is a breeder, owner and handler of top-winning Salukis and the author of 19 books. Send questions to D. Caroline Coile at breedersnotebook@bowtieinc.com.