In stark rebuttal to the growing “genetic diversity” cult in animal breeding (a thinly-veiled and politically motivated animal rights attack on purebreds) a study into Thoroughbred pedigrees contradicts an accusation levelled at purebred dog breeders, especially show breeders – that “pedigree worship” and the overuse of popular sires and subsequent inbreeding to consciously concentrate the genes of specific dogs is responsible for a phenomenon called “bottlenecking” and a loss of genetic diversity.
What is bottlenecking? When one does extended pedigree research to discover all the animals in a population trace a great preponderance of their ancestry to a handful of ancestors, making them all highly inbred and closely related, no matter what the first 4 generations of a pedigree indicate for ancestors. For example, 10 generation pedigrees in my breed often produce COI – “coefficient of inbreeding” calculations exceeding 50% – mathematically indicating that the dog is more inbred than if it were produced by a father to daughter mating.
(A dog pedigree with COI shown – the “bottleneck” sire Ch.Sky Rocket’s Upswing will repeat dozens of times if you follow all of the lines back through the generations.)
The theory is that genetic bottlenecks are created of arbitrary decisions of breeders to inbreed for short term gain or simple “beauty traits” (making show breeders the convenient villains) and that the phenomenon can be prevented by intentionally low COI matings and selection for performance traits – argued to be highly complex and thus, destroyed by intense homozygosity (inbreeding).
The political aspect enters when the diversity cultists argue that breed organizations and governments prohibit breeders from using inbreeding as a methodology – this is already occuring in some European countries as the animal rights movement conquers old battlefields and goes looking for new ones.
Well, meet the Thoroughbred.
2003 Kentucky Derby winner Funny Cide
Seldom closely inbred, the history of the high performance Thoroughbred is well known and documented. Stud books have been maintained for centuries. The breed was founded on three sires of the 17th century, the Darley Arabian, the Byerly Turk and the Godolphin Barb. Dna evidence has now confirmed what was already suspected by pedigree researchers;
According to a study published in The Irish Times on Dec. 13, 2001, “the Darley Arabian can lay claim to 95 percent of the paternal lineages.”
The Darley ArabianThe study, using DNA analysis, traced the lineage of a million British horses dating back two centuries, in the largest analysis of pedigrees made.
“The most striking thing is that we were able to confirm the dominance of the three most important founder stallions, but what is new is that one of them is responsible for 95 percent of all the male lineage,” said Patrick Cunningham, professor of animal genetics at Trinity College, where the study was conducted.
The role of performance selection has not prevented the bottleneck effect – indeed, it may have created it. When animals are chosen for breeding on the basis of highly specific traits, be they aesthetic or performance related, the sons of one sire will tend to outperform those of others and will gradually push out their lines.
Horse breeders did not know they were concentrating their lines to one sire to this extent, nor were they doing so intentionally. The theory of performance driven breeding should have resulted in a fairly even distribution of the three founding sires – instead, two lines are nearly extinct.
The phenomenon has been repeated in every species traced, including relatively “inbred” humans where it is thought that our gene pool passed through a prehistoric bottleneck of about 1000 ancestors and where Ghengis Khan has an estimated 16 million descendants.
Not that this suggests you should go cruising for chicks at the family reunion.