I have been asked about Popular Sire Syndrome, so here's my understanding.
(just speaking about dogs)
Each dog inherits its genes from its parents - two copies from each. The genes give the dog its distinctive qualities, bodily function, temperament, appearance, performane etc. Out of the thousands and thousands of genes that make up the dog, some are dominant and some recessive. The dominant ones show up immediately while the recessive one only show up when they meet up with another recessive at the same place in the dogs' DNA.
The Popular Sire is a Big Winner, he is much admired by everyone as being as near perfect as you can get (Judges have said so!!). He has a string of titles, everyone wants to use him and most of his puppies display his good qualities and become big winners too. Everyone who is someone has the Popular Sire in their puppies' pedigrees - it looks good! Everyone is happy!
BUT one generation on, where do breeders go? The dogs are half siblings - never mind.... my big winner and yours will produce even more big winners with Popular Sire on both sides of the pedigree!! Can't go wrong, can it?
Yes it can! All dogs carry detrimental genes - some serious, some not so much. If detrimental genes become obvious, we avoid them, but many are recessive and do not show, so we don't know they are there until they meet up - one from the sire and one from the dam - each parent being a carrier.
The Popular Sire passes on his good genes AND his bad genes. He does it very quickly, spreading them into perhaps all, or most, of the 'lines' of a breed. This is made possible by the ease of transport and through competition and publicity etc, these days. Hey! We all know about Popular Sire! We even import his sperm if we can't get our bitches to him!!
In former times the Big Winner moved in relatively small areas and was used over a longer period of time - time to evaluate his progeny and he himself!
The sire is not responsible for the whole puppy, its dam has an equal input and, rather than jumping on the bandwagon to get that name in the pedigree, breeders should take a much more care in choosing a stud that fits in with their brood bitch.
So what should we do?
1) Study carefully why a dog is a Big Winner
2) Study the Breed Standard, including function, and decide which points in your bitch (which is, of course IS the Best!) need strengthening.
3) Be aware that in reducing the number of individuals in a puppy's pedigree (in/close-breeding) you reduce the diversity of the gene pool.
4)The chance of producing something bad increases with every generation on, but that bad thing, when it shows up, will already be a problem and be widespread!
5) Not least - by concentrating on Popular Sire, many quality potentional studs are ignored - Quality dogs who have much to offer - specially a necessary contribution to the diversity of the gene pool.
It is not so difficult to find an Irish Setter stud given the great number of Irish Setters there are around the world - consider the plight of IRWS! Good studs are like gold dust! However, in the analysis of the breeding in 2006, out of the 18 litters bred in the UK, 2 dogs had sired 2 litters, 1 dog had sired 3 litters and 15 litters all had a different sire. In IRWS we are very conscious of the gene pool and breed diversity!
How do you see the Irish Setter gene pool and its breed diversity?