The Frontal Cortex

The Genetics of Race Horses

I always assumed that the best race horses simply had the best genes. It seemed like the kind of domain where nature trumped nurture, where the genetics of fast twitch fibers and heart size was more important than the details of training. But my assumptions were exactly backwards:

The offspring of expensive stallions owe their success more to how they are reared, trained and ridden than good genes, a study has found.

Only 10% of a horse’s lifetime winnings can be attributed to their bloodline, research in Biology Letters shows.

By far the biggest factor was the horse’s environment – the way they were trained, the choice of races entered and which jockeys were employed.

Hat Tip: Kottke


  1. #1 Emily
    December 20, 2007

    Yet I bet more than 10% of the horse’s dollar value and eventual stud fee can be attributed to bloodline.

  2. #2 Coturnix
    December 20, 2007

    Yes, all the current racehorses are descendants of 3 stallions and ~100 mares about two centuries ago. Thus, all thoroughbreds are essentially clones – the same deck of cards reshuffled over and over again. Sure some of the reshufflings make byas and others chestnuts, some are sweet, some are nasty, and yes, some may be a little faster than others, but the differences are miniscule, i.e., so small that environment can easily trump those differences.

  3. #3 dave X
    December 20, 2007

    Aren’t the racing horses a pretty small subset of all horses? A trainer or jockey couldn’t make a Clydesdale win, but race horses have been bred and selected for their fast-twitch fibers and endurance tuned far beyond the genotypic horse.

    It seems that once you are racing a pool of 30th generation racehorses, then nurture would have a significant effect. or

  4. #4 The Ridger
    December 20, 2007

    Most thoroughbred breeders really don’t know much about the genetics, anyway. First off, many mares are never raced at all. Then handicapping makes it hard to judge the horses – and the habit of racing them as adolescents means it’s hard to judge their ability and how they’ll pass it on. Think of the number of brilliant stallions whose sons are mediocre. It’s not for nothing that Tbred breeders talk about “catching lightning in a bottle” – it’s a crapshoot.

  5. #5 Dave Briggs
    December 21, 2007

    I am not surprised that you are surprised! I would have thought the same thing, but I was in bodybuilding for 10 years and saw the nurture side first hand. I trained at Gold’s gym in Venice California, amongst the biggest and strongest in the world. I also trained professional bodybuilders there.
    Genetics is sited by those that don’t move up the ranks as quickly as they would like, not knowing the real secret. The secret is train like you are trying to kill your body and then give it all the nutrients it needs to survive and grow. Genetics plays a certain role, you have to have 2 arms and 2 legs, etc., but it is what is done to your physiology that makes the difference.
    Look at Arnold. I saw the first file he ever made and even he would agree that he was about the most awkward, nervous actor anyone had ever seen. He used the same determination in the films as the bodybuilding and look where he got.
    Psychology has been debating nature or nurture for decades, and they both have their place. But in the physiological realm, bodies were made to adapt.
    Dave Briggs :~)

  6. #6 Vnend
    December 22, 2007

    Not exactly playing fair with the stats, but, in almost any form of competition, 10% is a huge advantage. The Kentucky Derby takes about 2 minutes to run, but a horse that is 12 seconds off that pace isn’t going to be on the track. Genetics may “only” account for 10% of the difference, but when the margin of victory is 1% and less…

    Bottom line? To be successful enough to make money in a competitive environment you need all the help you can get. Starting out with a strong bloodline isn’t going to ensure success, but that 10% is an edge people want.

  7. #7 Pawlie Kokonuts
    December 22, 2007

    Not surprising to me. (I was tempted to sign as Bob Bafford, the famous horse trainer, but, um, …my upbringing prevented me.)

  8. #8 john macmillan
    August 21, 2010

    I train racehorses and used to be a jockey, I was always told the difference between good trainers/jockys was not that they got slow horses to win,but that they did not get fast ones beaten!! From what I have seen there are a lot of very small factors which can help to win a race so even if genetics is only a small part it still matters

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