If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
How do dog breeders breed dogs?
I've looked around for a NG devoted to discussing the finer points of
breeding but have been unable to find one. Hopefully this one has enough serious breeders to suggest answers or even better, provide an authoritative rebuttal. The problem is the following post, posted in another NG, which was in response to a serious scientific study which allegedly has found an "intelligence gene" in persons of Jewish ethnicity. I don't wish to enter into a discussion of that fact, right or wrong, nor into the other biological details, most of which are over my head. I was however struck by the characterization of dog breeding which I believe to be erroneous. I'd like the input of someone more knowledgeable than I on this point. Hence this post. Begin quote********* Well, the Tay-Sachs part, yes. But the idea that inbred groups of people might differ from each other in their (various) mental abilities as much as they do appearance, height, and physical abilities, doesn't seem that far-fetched to me. As I said, after all, beagles are pretty dumb. And border collies, on average, are pretty darn smart. I agree that inbred groups are likely to have disproportionate ratios of some alleles, but you need pretty heavy selection to get the kind of uniformity you see in a dog breed. You can see a little of such selection where a population has lived in a particular climate for a very long time, but it's selection for only a few traits, like heat loss or resistance to malaria. These ethnic groups are generally as diverse as anybody else otherwise, as can be seen from blood group and HLA markers. You can't select for everything, when creating a breed. Border collies were selected for their intelligence and willingness to cooperate with the shepherd, alertly noting his signals and obeying them. Beagles were selected for acute sense of smell and willingness to follow a scent. These traits are exaggerated forms of behaviours found in wolves. Beagles are useless as sheepdogs, and border collies are lousy trackers. Note that desirable traits have to be continually maintained by selection -- most working breeds of dogs have separate populations now, show dogs selected for their conformity to the written standards for appearance and working dogs, which are selected to maintain the behaviour traits for which the breed was developed. To create a uniform population like a dog breed, you start with a very small initial population, usually only a few individuals, inbreed very closely (parent to child, parent to grandchild), and select strongly for desired traits, discarding all but a few best matches to your ideal when deciding which animals will produce the next generation. These conditions don't occur naturally, especially not in humans. Even small populations on islands and religious groups that practice complete endogamy avoid inbreeding as much as possible and don't practice artificial selection. They begin to show unusual rates of a few genetic traits, usually undesirable ones, after many generations, and a very small island population may start to have a sort of family look about them, but they are nowhere near as uniform as an animal breed. Jews are a very poor candidate for a human "race" or "breed". It's long been established that genetically they are closely similar to the ethnicities they live among, and for obvious reasons. There's some effect due to migrations in the past thousand years, as Jews were expelled from most western European countries in late medieval times and moved east and south. But even visually, eastern European Jews look like eastern Europeans, North African Jews look like North Africans and Chinese Jews look like Chinese. Blood group data demonstrate this very clearly. As for all these Nobel laureate Jews, well, I can assure you that there is no shortage of Jews who are not so smart. If a culture very strongly values a trait, members of that culture will be pushed to develop that trait in themselves, and rewarded for doing so, and those individuals with talent in that direction will have the opportunity to excel. This applies to any talent or trait -- intellectual ability, athletic ability, aggressiveness, artistic talent, religious tendencies, whatever. The Scandinavians are the same people they were 800 years ago, but they are no longer noted for the ability to go into berserk rages and slaughter the defenseless in droves oblivious to their own safety, although this was a prized and widely expressed talent in Viking times. This notion that Tay-Sachs is associated with intelligence is just hand waving, as far as I can see. Until there's some actual data, we have no reason to believe it's anything but wishful thinking. I've also heard the theory that Tay-Sachs is associated with resistance to tuberculosis, another link for which there's no evidence. I suspect that Tay-Sachs is just another bad recessive trait that hasn't had enough selection against over long enough time to be eliminated. Against the Third World like conditions that prevailed in Europe until a few generations ago -- large families and high mortality rates in infants and young children -- deaths from Tay-Sachs would be lost in the noise. People don't select themselves for desirable traits, after all. Even if a culture strongly values some trait, and rewards men who excel at it with greater opportunities to contribute to the next generation, most everybody, and almost all women, still marry and have children. You may want to marry the person who best displays the ideal of your culture, but you'll settle for what you can get. You don't make any progress in developing a genetically uniform population, like a livestock breed, that way. Jews, like any disfavored group, tell just-so stories to comfort themselves. One is to point out that in medieval Europe, people with noted intellectual talents would enter monasteries and leave the gene pool, presumably making the general population stupider than the Jews. This of course ignores the fact that most medieval Europeans were peasants who had no opportunity to express scholarly abilities in monasteries or elsewhere, and most people who became monks or nuns did so for other reasons and found reading a real chore, if they ever became literate at all. Another just-so story is that the prohibition on pork is a wise tradition, or even an example of special divine consideration, for preventing trichinosis. Well, an injunction to boil water before drinking it, or the inside word on smallpox vaccination would have saved orders of magnitude more lives that trichinosis could ever have taken. Incidentally, most cases of Tay-Sachs now occur amongst people of French Canadian origin, because Jews are using modern techniques to select against it in themselves. I sincerely doubt that the Jews are getting stupider, or the Quebecois are getting smarter. (Btw, it would be easy to test this theory that Tay-Sachs heterozygotes have better intellectual abilities than others. Find a bunch of high school students who are self-identifying Jews and offer free Tay-Sachs testing in exchange for a peek at their SAT scores. It shouldn't be difficult to find many thousands of subjects, and if there's a real correlation, there should be a significant difference in Tay-Sachs rates between the upper and lower tenth percentile. Betcha there isn't, but nobody knows until somebody does the research.) End quote*************** |
#2
|
|||
|
|||
I think you'll find the more serious discussions of dog breeding in the
email groups for the various breeds, rather than on the NGs. This is because of those pesky little alleles; the ones that most concern a Golden Retriever breeder are not necessarily the ones that most concern the Chihuahua breeder. Tha Canine Genome project has now wound up and the next step, the Canine Phenome project is in it's earliest phases... and will concentrate on the individual breeds and their genetic patterns. National breed clubs are scurrying to put together the money for their breeds' participation.... This is where our hope to work away from genetic problems lies, given that the same problem can vary from breed to breed in it's genetic cause.... and that some disorders are almost limitted to one or two breeds. Good luck in finding a "home" where the topic fits well.... Jo Wolf Martinez, Georgia |
#3
|
|||
|
|||
Jo Wolf said in rec.pets.dogs.breeds:
I think you'll find the more serious discussions of dog breeding in the email groups for the various breeds, rather than on the NGs. This is because of those pesky little alleles; the ones that most concern a Golden Retriever breeder are not necessarily the ones that most concern the Chihuahua breeder. There are more than a few extremely knowledgeable-about-genetics posters here. Good luck in finding a "home" where the topic fits well.... OP: You don't have to take the discussion elsewhere, just give it a few days for the posters I mentioned to show up. "Intelligence genes," as they pertain to *dogs* will be an interesting topic for this group. -- --Matt. Rocky's a Dog. |
#4
|
|||
|
|||
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Missing his parents | Lemony Fresh | Dog behavior | 7 | March 3rd 05 05:03 AM |
male/female German Sheperd agressive behavior | tux | Dog behavior | 69 | June 24th 04 08:47 PM |
light reading dogs giets | Alpha | Dog behavior | 0 | March 3rd 04 09:41 PM |
light reading dogs giets | Alpha | Dog behavior | 0 | March 3rd 04 09:41 PM |
light reading dogs giets | Alpha | Dog behavior | 0 | March 3rd 04 09:41 PM |